Patented Optical Design Delivering Ultra High-Resolution Height Measurement Line Confocal Imaging (LCI) technology is a patented optical metrology ...

The proposed single-phase microstructure in Fig. 2a has the advantage of being easy to fabricate while effectively realizing a non-zero C56. However, it is also possible to design metamaterial microstructures with different geometries or materials (see Supplementary Fig. 6 for other microstructure candidates). In addition, we choose aluminum as the target isotropic background material and 100 kHz as the target resonance frequency in Fig. 2b–e. However, the proposed coupled resonance is applicable to other materials and frequencies (see Supplementary Note 6 for the applicability and limitation of the proposed method). Supplementary Table 2 provides the required physical properties of the anisotropic medium to realize the coupled resonance at various target materials and frequencies. The geometric parameters of the metamaterial microstructure with another geometric shape or at another target frequency can be obtained by utilizing the same shape optimization algorithm28.

Crampin, S. et al. Observation of dilatancy-induced polarization anomalies and earthquake prediction. Nature 286, 874–877 (1980).

I am a beginner and i own a canon 750d with 18-55 lens. Thinking it is inadequate, i have a plan to buy a zoom lens. Have two options, both used lens 1. Canon 55-250 2.Canon 75-300 f/4-5. 6 Please help me choose one. And also is it advisable to buy a used lens?

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Most comments from from subjective consumerist mentality. Some are thoughtful, logical and correct. Just clickbait anyway and technically makes little sense and of course the grammar ‘ gotten ‘ etc. ( a meaningless contradictory term ) It is of course American, not English

Such lenses will let in twice to three times as much light as a fast professional zoom lens with an aperture of f/2.8. While many zoom lenses feature optical image stabilization systems to help you in low-light conditions, such systems are useless if you have a moving subject.

Singh, R. et al. Improving the contrast ratio of OLED displays: an analysis of various techniques. Opt. Mater. 34, 716–723 (2012).

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Hi, I am planning to buy Nikon D5600. I prefer to click candid shots. It can be person, landscape or traffic, I shoot birds rarely. Monuments are of utmost interest to me to tell history. May I know what lenses should I buy.

On many consumer zoom lenses, you will often see something like f/3.5-5.6, which represents the maximum aperture of the lens at different focal lengths. For example, a lens like Nikon 18-55mm f/3.5-5.6 will have a maximum aperture of f/3.5 at the shortest focal length of 18mm, while at the longest range of 55mm, its aperture will be limited to f/5.6.

In more detail, condition (1) is required to suppress the transmission and reflection of longitudinal waves under the shear wave incidence, and it can be satisfied by zero longitudinal-shear mode-coupling stiffness constants of the metamaterial (i.e., C15=C16=0). Condition (2) is necessary to accomplish the magnitude balance between transmitted SV and SH waves in the isotropic background. To this end, the slow and fast eigenmodes should be polarized in two diagonal directions in the y–z plane. If the eigenmodes are not diagonally polarized in the y–z plane, the magnitudes of slow and fast eigenmodes are determined differently, leading to distorted circular polarization (see Supplementary Fig. 1). For diagonal polarization inside the metamaterial, its shear stiffness constants of SV and SH waves should be equal (i.e., C55=C66). The detailed derivation is described in Supplementary Note 2. The intermediate conclusion so far is that conditions (1) and (2) can be achieved with C15=C16=0 and C55=C66, respectively.

Agreed. After getting bit more into photography, I am not happy about the kit len, specially it can’t go below f4 most of time, replacing it with a fast ones cost so much but adding a couple fast primes (like 24mm f2.8 and 50mm f1.8) with only a couple hundred dollars offer so much more for walk around shootings and more chances for creativity.

Crampin, S. & Peacock, S. A review of shear-wave splitting in the compliant crack-critical anisotropic Earth. Wave Motion 41, 59–77 (2005).

Lee, J., Kweun, M.“., Lee, W. et al. Perfect circular polarization of elastic waves in solid media. Nat Commun 15, 992 (2024). https://doi.org/10.1038/s41467-024-45146-w

Many beginner photographers often wonder why they do not seem to be able to get beautifully separated subjects when using their kit zoom lenses. Due to the small maximum aperture and lower quality lens optics, it is often impossible to get good-looking, “creamy” backgrounds with consumer zoom lenses.

Greenfield, N. J. Using circular dichroism spectra to estimate protein secondary structure. Nat. Protoc. 1, 2876–2890 (2006).

Kim, J. et al. Ultralight and ultra-stiff nano-cardboard panels: mechanical analysis, characterization, and design principles. Acta Mater. 248, 118782 (2022).

Most fast, professional zoom lenses, such as 14-24mm, 24-70mm and 70-200mm, have a fixed maximum aperture of f/2.8. Fast, professional prime lenses on the other hand, can go as wide as f/0.95. For this reason, they offer not just better light gathering abilities, but also shallow depth of field, which can result in photographs with beautifully rendered background highlights known as “bokeh“.

Many photographers believe that being forced to “zoom” in or out using the old-fashioned way, by walking, is a good way of learning composition and finding better angles. It also supposedly helps one get used to a lens better and use it to its full potential.

Cao, L., Wan, S., Zeng, Y., Zhu, Y. & Assouar, B. Observation of phononic skyrmions based on hybrid spin of elastic waves. Sci. Adv. 9, eadf3652 (2023).

a, The fabricated aluminum-metamaterial-aluminum sandwich system. The bottom right inset represents a zoomed-in cylindrical hole array (the scale bar is 10 mm). b, The installation of the shear-wave ultrasound actuator. c, The measured time-transient output shear-wave displacement through the metamaterial (normalized to the magnitude of the input shear-wave displacement). The measured data is indicated by dots that change color from blue to red over time phase ϕt, while the theoretical steady-state displacement trajectory assuming full transmission is indicated by a magenta circle.

If everything were in favor of prime lenses, no one would use zooms. Despite their extra weight and cost, they are extremely popular and can be very convenient to use. There are several areas where even the best fixed focal length lenses have no way to beat a good zoom. Below are the advantages offered by variable focal length lenses.

Thanks to this, choosing between a zoom and a prime lens is now harder than ever. In this beginner guide, I talk about prime versus zoom lenses in detail, explaining their differences, along with some image samples.

Savage, M. K. Seismic anisotropy and mantle deformation: what have we learned from shear wave splitting? Rev. Geophys. 37, 65–106 (1999).

where ϕL and ϕS are the phase correction of longitudinal and shear waves for wave propagation through the metamaterial, respectively. Here, we define the transmission (reflection) coefficients of L, SV, and SH waves as tL, tSV and tSH (rL, rSV and rSH). For the generation of exact circular polarization, the transmission coefficients of two shear waves should satisfy \(|{t}_{{{{{{\rm{SV}}}}}}}|=|{t}_{{{{{{\rm{SH}}}}}}}|\) and \(|\angle {t}_{{{{{{\rm{SV}}}}}}}-\angle {t}_{{{{{{\rm{SH}}}}}}}|=0.5\pi\). For full energy efficiency of the polarization conversion, all other transmission and reflection coefficients except tSV and tSH should be zero, i.e., \({t}_{{{{{{\rm{L}}}}}}}={r}_{{{{{{\rm{L}}}}}}}={r}_{{{{{{\rm{SV}}}}}}}={r}_{{{{{{\rm{SH}}}}}}}=0\). The scattering matrix is determined by the physical properties of the anisotropic metamaterial29,30,31. In Fig. 1d, we used the physical properties of the metamaterials as \(\rho=2107\,{{{{{{\rm{kg}}}}}}}\,{{{{{\rm{m}}}}}}^{-3}\), \({C}_{55}={C}_{66}=21.1\,{{{{{\rm{GPa}}}}}}\), and \({C}_{56}=-12.6\,{{{{{\rm{GPa}}}}}}\).

Thus before buying a lens, it might be worth checking out our lens reviews, although most modern lenses are indeed sufficiently sharp.

But, if you need a single lens for a variety of applications, a zoom lens would likely be better. That’s why most wedding shooters simply love 24-70mm f/2.8 zooms, since this range on a full-frame camera can do almost everything from group shots to portraits.

As an elastic analogy of an optical birefringent plate, in 1964, Einspruch proposed a conceptual scheme for generating a circularly polarized elastic wave using tungsten buffers1. However, the classical birefringent plate has an intrinsic trade-off between its bulkiness and the accuracy of the circularly polarized elastic waves it generates. The elastic birefringent plate is typically bulky because elastic waves in solids have much longer wavelengths than electromagnetic waves. Strong birefringence is required to avoid bulkiness, but it inevitably sacrifices the accuracy of the generated circular polarization. The detailed theoretical analysis of the intrinsic limitations of the classical birefringent plate is described in Supplementary Note 1. Since the first identification of shear-wave splitting due to the seismic birefringence of the Earth’s crust2 and upper mantle3 in 1980, the observation of elliptically or circularly polarized elastic waves in the anisotropic Earth has been studied for decades4,5,6. In addition, some researchers have reported the realization of circularly polarized elastic waves in metals at low temperatures7 and artificially structured chiral materials8,9,10,11,12. Despite these efforts, the utilization of circularly polarized elastic waves is still difficult due to the lack of a method to effectively generate elastic circular polarization in common isotropic solids, which constitute most load-carrying elements in engineering applications.

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a Schematic diagram of a 3D anisotropic elastic metamaterial sandwiched by an isotropic background to realize the perfect polarization conversion from linear to circular. The anisotropic metamaterial is composed of obliquely perforated microstructures. b Schematic diagram of the coupled resonance theory. The total displacement field (green) inside the anisotropic metamaterial is decomposed into the displacement fields of the half-wavelength-matched slow eigenmode (yellow) and quarter-wavelength-matched fast eigenmode (orange). c Physical properties of the anisotropic metamaterial satisfying the derived theoretical conditions with respect to nSE and nFE. The isotropic background is aluminum. d Frequency responses of the transmission coefficients under the SV wave incidence to the anisotropic metamaterial satisfying the coupled resonance theory with \({n}_{{{{{{\rm{SE}}}}}}}={n}_{{{{{{\rm{FE}}}}}}}=1\).

Heffern, M. C., Matosziuk, L. M. & Meade, T. J. Lanthanide probes for bioresponsive imaging. Chem. Rev. 114, 4496–4539 (2014).

Very informative as always. However, newcomers to this hobby would not be prepared to spend lots of money of Canon L lens if they have little knowledge of how to use their gear competently so it would make more common sense to not just show expensive lens like the the two you used to entice us to open your post!

We evaluated the effective physical properties of the designed 3D anisotropic metamaterial to confirm that the metamaterial is compatible with the proposed coupled resonance theory. To this end, we extended the scattering parameter retrieval method, which was established for 2D elastic metamaterials29,30,31, to 3D elastic metamaterials (see Methods for details). The calculated effective density and stiffness constants of the designed metamaterial are \(\rho=3024 \, {{\rm{kg}}}\space{{\rm{m}}}^{-3}\), \({C}_{55}={C}_{66}=16.6 \, {{{{{\rm{GPa}}}}}}\), and \({C}_{56}=-4.7 \, {{{{{\rm{GPa}}}}}}\) at the frequency of 100 kHz. Through the effective physical properties of the metamaterial, the phase changes of the slow and fast eigenmodes through the metamaterial were estimated as \(\varDelta {\phi }_{{{{{{\rm{SE}}}}}}}=2.004\pi \, \approx \,2\times \pi\) and \(\varDelta {\phi }_{{{{{{\rm{FE}}}}}}}=1.499\pi \, \approx \,3\times 0.5\pi\). In other words, the metamaterial fulfills the coupled resonance theory with \({n}_{{{{{{\rm{SE}}}}}}}=2\) and \({n}_{{{{{{\rm{FE}}}}}}}=3\), which eventually leads to perfect polarization conversion from linear to circular in aluminum. Figure 2e shows that the simulated transmission spectra of the metamaterial correspond well with the theoretical transmission spectra that exhibit the coupled resonance with \({n}_{{{{{{\rm{SE}}}}}}}=2\) and \({n}_{{{{{{\rm{FE}}}}}}}=3\) at 100 kHz.

A zoom lens, on the other hand, has a variable focal length. By turning the zoom ring, you move optical elements inside the lens to achieve a different angle of view. This means that you can make objects appear larger by turning the zoom ring in one direction, or fit more objects into the frame by turning it in the opposite direction.

Though I’m not a professional photographer but still I would like to discuss some issues about prime and zoom lenses which may not exactly like you told us here.

Beginner photographers are often faced with a choice between buying a fixed focal length lens or a zoom lens. As you can see from this article, both have their advantages and disadvantages, so choosing between the two can be quite difficult indeed.

Shear-wave ultrasound actuators (Olympus® V1548) with a diameter of 25.4 mm were bonded on the left and right sides of the specimen by shear-wave couplant (Olympus® SWC-2). An SV wave with a 5-cycle sinusoidal waveform was generated by the function generator (Agilent Technologies 33220 A). The transmitted SV and SH waves through the metamaterial were recorded by the digital oscilloscope (LeCroy WaveRunnerTM 620Zi). The signal transmitted through the metamaterial in Fig. 3c was normalized to the signal transmitted through the reference aluminum specimen (\(200\times 200\times 400 \, {{{{{{\rm{mm}}}}}}}^{3}\)) without the metamaterial. The average value of a total of five measurements was used.

Commercial software (COMSOL Multiphysics) based on finite element analysis was used for the numerical analysis. For the physical properties of aluminum, the mass density of 2700 kg m−3, Young’s modulus of 70 GPa, and Poisson’s ratio of 0.33 were used. In Fig. 2b, periodic conditions were applied in the y- and z-directions while waves propagated in the x-direction, and low-reflecting boundaries were applied on the right and left ends of the simulation model. Color surfaces in Fig. 2b, c represent normalized displacements (normalized to the displacement magnitude of the incident wave), and black arrows represent total displacement vectors. In Fig. 4, the specimen is an aluminum cube with a side length of 150 mm. The crack-like defect is a cavity with a size of \(30\times 3\times 100\) mm3. The size of the transducer is \(10\times 100\times 100\) mm3. The size of the metamaterial is also \(10\times 100\times 100\) mm3. The shear-wave ultrasound transducer generates an enveloped 5-cycle sinusoidal SV wave with a center frequency of 100 kHz.

Generalist wildlife shooters also love zooms such as the new Nikon 180-600mm f/5.6-6.3, since it can capture a wide variety of subjects from large mammals to birds. Specialist wildlife photographers love primes like the 600mm f/4 because its speed, image quality, and fast aperture help a lot with smaller subjects like birds.

Chen, Y., Frenzel, T., Guennneau, S., Kadic, M. & Wegener, M. Mapping acoustical activity in 3d chiral mechanical metamaterials onto micropolar continuum elasticity. J. Mech. Phys. Solids 137, 103877 (2020).

I started years ago and used kit lens until I learned from experts like yourself what to do. Competent I am now ( in the wise words of Yoda…), I understand that it is the person behind the camera and not expensive L lens which get the job done. Nevertheless, if you have the money falling from a tree… Three I have.

where f indicates a frequency. Most importantly, we could explicitly determine the physical properties (ρ and C) of the anisotropic metamaterial from conditions (1), (2), and (3) as follows (see Supplementary Note 3 for derivation):

Model: IOS Semi-APO FLUO E-PLANDescription: Objectives for brightfield, darkfield and epifluorescence observationMagnification / Numerical Aperture• 4X ...

By the way all the professional mainly using fast primes for taking high quality images not for cheaper price, since fast primes have bigger aperture therefore not onlyelp in dim light situations but also provide shallower depth of filed and sharp image across the frame. Normally lenses with focal length less than 100 mm in most cases may weigh less than the zoom in the same focal length range, but those of 100mm up mostly are not so light than a zoom.

Prime lenses have a single specified focal length, like 50mm. They come in all kinds sizes and focal lengths, from fisheye to super-telephoto. Here are some of the most popular prime lenses for different camera mounts:

Surprisingly, many beginners often desire monstrous lenses like 70-200mm f/2.8 with image stabilization. True, these lenses are extremely sharp, have insanely fast autofocus motors and can survive plenty of abuse. However, they are also much more noticeable due to their sheer size, and their heavy weight can cause back and neck pain and even long-term injuries.

Deng, B. et al. Inverse design of mechanical metamaterials with target nonlinear response via a neural accelerated evolution strategy. Adv. Mater. 34, 2206238 (2022).

I prefer various focal points so I would use a zoom lens. I am a beginner at using my canon EOS system and taken a few pictures. I never really paid that much attention to the lens as long as the picture was a great shot. But reading up on the lens, I like the zoom over the prime.

The width, height, and length of the fabricated aluminum-metamaterial-aluminum sandwich system are 200 mm, 200 mm, and 400 mm. The cylindrical holes were directly machined by a super-drilling process with additional wire cutting (Mitsubishi DWC-300HA) and milling machining (DOOSAN MYNX 6500). Three different-sized holes were arranged at an interval of 5.43 mm along the x-axis parallel to the wave propagation direction, and forty-five hole arrays were arranged at an interval of 4.36 mm in the diagonal direction along the positive y- and positive z-axis. Considering the hole-size limit of the fabrication, the radii of the cylindrical holes of 1.43 mm, 1.73 mm, and 1.47 mm were determined.

Those fast primes, say those telephotos which have focal length more than 100 mm normally are much more expensive than the zooms of the same focal length range. You see one 100mm f2and one 200mm f2 ou f4 are not cheaper than a 70-200mm zoom: Sony 100-400 mm zoom is cheaper than Sony 400mm prime and Sony 200-600mm zoom also is cheaper than one 60mm prime!

As an unprecedented application of a circularly polarized shear wave in non-destructive testing, we suggest the detection of arbitrarily oriented cracks, which are difficult to detect using a linearly polarized shear wave alone. In ultrasonic non-destructive testing, the crack is detected by receiving the reflected ultrasonic shear wave from the crack. Nonetheless, it is impossible to detect the crack using a linearly polarized shear wave if the polarization direction and the orientation of the crack are parallel32. To overcome this limitation in non-destructive testing, we propose employing a circularly polarized shear wave, as illustrated in Fig. 4a. Here, we used finite element analysis to simulate ultrasonic testing. Notably, a circularly polarized shear wave can interact with cracks of any orientation because its polarization direction rotates in space and time. For comparison, reflected signals from parallel, diagonal, and perpendicular cracks are simulated with and without the use of circular polarization, as shown in Fig. 4b. The signal reflected from the crack was extracted as the difference between the reflected signals with and without the crack. Without the use of a circularly polarized shear wave, the presence of the parallel crack cannot be identified because there is no reflected signal from the parallel crack. However, a circularly polarized shear wave can distinguish all the reflected signals from parallel, diagonal, and perpendicular cracks. Cracks of any orientation can now be inspected at once using circular polarization, allowing for faster and more accurate ultrasonic non-destructive testing.

An IR lens captures infrared light that is virtually impossible to see with the naked eye. While a normal camera lens captures images of objects that radiate ...

a An illustration of crack-like defect detection using linearly polarized (left) and circularly polarized (right) shear waves. θ represents the orientation of the crack. b The simulated reflected signals from parallel, diagonal, and perpendicular cracks without (left) and with (right) the proposed metamaterial. The specimen is aluminum, and the metamaterial designed in Fig. 1d is used at 100 kHz.

Chen, H., Fung, K. H., Ma, H. & Chan, C. Polarization gaps and negative group velocity in chiral phononic crystals: layer multiple scattering method. Phys. Rev. B 77, 224304 (2008).

Very good article. I have gone the zoom route for the incredible versatility. Many many situations do not allow to zoom with your feet. I have bought 3 zooms and all are top quality zooms from 10 to 400mm. I do have 2 primes, a fisheye and a 100mm f2.8 L macro. For me this works great but I believe everyone should make their own choice. Again a good article. Thank you.

In this paper, the concept of elastic metamaterials15,16 is utilized to implement the proposed coupled resonance within an anisotropic medium. 3D micro-structuring of elastic metamaterials has provided overwhelming physical properties beyond common homogeneous materials, such as strong ultralight behavior17,18, auxetic behavior19,20, nonlinearity21,22, mechanical chirality23,24, and fluid-like behavior25,26. We propose an obliquely perforated microstructure of a 3D anisotropic elastic metamaterial to simultaneously exploit two distinct resonances. Numerical analysis verifies that the coupled resonance theory is realizable with the proposed 3D anisotropic elastic metamaterial. We fabricated an aluminum-based metamaterial composed of hundreds of high-aspect-ratio holes for experimental validation. We observed circularly polarized ultrasonic shear waves at one end surface of an aluminum-metamaterial-aluminum sandwich system under the linearly polarized shear wave incidence at the other end surface. Ultrasonic shear waves have been widely used for structural health monitoring and nondestructive testing27. Traditionally, the generation of shear waves has been limited to linear polarization along specific directions. This limitation presents a notable drawback: such waves are ineffective in detecting cracks aligned parallel to their polarization direction. Building on our findings presented in this study, we will show that the use of circularly polarized shear waves can identify cracks that remain undetected by their linearly polarized counterparts.

Reinbold, J., Frenzel, T., Munchinger, A. & Wegener, M. The rise of (chiral) 3d mechanical metamaterials. Materials 12, 3537 (2019).

Multiple sets of physical properties of anisotropic metamaterials for the perfect polarization conversion in isotropic aluminum (\({\rho }_{0}=2700\,{{{{{{\rm{kg}}}}}}}\,{{{{{\rm{m}}}}}}^{-3}\), \({C}_{55}^{0}={C}_{66}^{0}=26.3\,{{{{{\rm{GPa}}}}}}\), and \({C}_{56}^{0}=0 \, {{{{{\rm{GPa}}}}}}\)) are depicted in Fig. 1c. The target resonance frequency and metamaterial thickness were chosen as \(f=100\,{{{{{\rm{kHz}}}}}}\) and d = 0.01 m, respectively. In Fig. 1d, we calculate the transmission spectra of the metamaterial with nSE=nFE=1 where tSV and tSH denote transmission coefficients of SV and SH waves. The result demonstrates that the magnitude balance (\({|{t}_{{{{{{\rm{SV}}}}}}}|}^{2}={|{t}_{{{{{{\rm{SH}}}}}}}|}^{2}=0.5\)) with the 90° out-of-phase relation (\(|\angle {t}_{{{{{{\rm{SV}}}}}}}-\angle {t}_{{{{{{\rm{SH}}}}}}}|=0.5\pi\)) is achieved at the resonance frequency of 100 kHz, resulting in the generation of exact circular polarization in isotropic aluminum with full energy efficiency. See Supplementary Note 4 and Supplementary Figs. 2 and 3 for transmission and reflection responses of the metamaterial over the broader frequency range of 0 to 400 kHz.

A fast prime lens will allow you to shoot subjects in low light environments without introducing blur, thanks to a larger / wider aperture. Due to typically simpler optical designs, prime lenses can easily “open” up to f/2 or even f/1.2.

Noting that the spinning nature of elastic waves has recently received considerable attention41,42,43,44,45,46,47,48, our findings can be a promising strategy to efficiently generate various elastic spins. For instance, it may be possible to generate a circularly polarized bulk shear wave from a linearly polarized bulk longitudinal wave by comprehensively utilizing the longitudinal-to-shear mode conversion and the linear-to-circular polarization conversion. Furthermore, in a special 3D solid medium with the same longitudinal and shear stiffness, a novel circularly polarized bulk elastic wave composed of longitudinal and shear waves can be observed.

So what’s the really reason? If we analize then we will find out that all the decisive point is lying on the maximum aperture of the lens but not because of whether it is a prime ou zoom. We all know the nikon 58mm f0. 95 noct costs 9000 dollars and it’s a standard prime and it’s much more expensive than the nikon 2470f2.8 zoom!

Ando, M., Ishikawa, Y. & Wada, H. S-wave anisotropy in the upper mantle under a volcanic area in Japan. Nature 286, 43–46 (1980).

buy the canon 100 to 400 usm f4.4 / 5.6 you wont be dissapointed ,I have been using one for 6 years now on wildlife coupled with a canon 7d and just love it

Unlike the lack of exploration in circularly polarized elastic waves, circularly polarized light has been intensively explored and fertilized optical techniques that linearly polarized light cannot do, including 3D projection33, high-performance display34,35, high-resolution molecular structure analysis36,37,38, and quantum computing39,40. Accordingly, our work is expected to open a new horizon for the elastic version of all circular-polarization-based optical devices. As an example of a potential application, the detection of an arbitrarily oriented crack using circularly polarized ultrasonic shear waves, which is otherwise difficult to realize, was demonstrated.

When a linearly polarized elastic wave propagates in the x-direction through a 3D isotropic solid, waves in which the medium vibrates in the x-, y-, and z-directions are referred to as longitudinal (“L”), shear horizontal (“SH”), and shear vertical (“SV”) waves, respectively. A circularly polarized elastic wave is a combination of two orthogonal linearly polarized elastic waves that have the same magnitude and propagation speed but a 90° phase difference. In an isotropic solid, however, longitudinal waves always propagate faster than shear waves. Consequently, elastic circular polarization can be formed by only two shear waves, SV and SH waves, propagating at the same speed. Our idea is to realize a perfect conversion between linear and circular polarization of shear waves, as well as the decoupling between longitudinal and shear waves in a target isotropic solid (mass density of ρ0 and stiffness of C0) by introducing a 3D anisotropic elastic metamaterial (effective mass density of ρ, effective stiffness of C, and thickness of d), as depicted in Fig. 1a.

At the incident interface of the metamaterial, a linearly polarized shear wave splits into two shear eigenmodes formed inside the metamaterial, as shown in Fig. 1b, which play a crucial role in the generation of circularly polarized shear waves. For the analysis, we defined a slow one as a slow eigenmode (“SE”) and a fast one as a fast eigenmode (“FE”) among two shear eigenmodes. Remind that a circularly polarized shear wave is the sum of two linearly polarized shear waves of equal magnitude but 90° out-of-phase. Thus, the slow and fast eigenmodes should satisfy the following three conditions for perfect linear-to-circular polarization conversion: condition (1) is that the slow and fast eigenmodes should not be coupled with the longitudinal eigenmode; condition (2) is that the slow and fast eigenmodes should be polarized with the same magnitude; condition (3) is that the slow and fast eigenmodes should be fully transmitted through the metamaterial with a 90° phase difference.

Canon telephotolensfor wildlife

Lee, J. & Kim, Y. Y. Elastic metamaterial for guided waves: from fundamentals to applications. Smart. Mater. Struct. 32, 123001 (2023).

Svanberg, K. The method of moving asymptotes–a new method for structural optimization. Int. J. Numer. Methods Eng. 24, 359–373 (1987).

Nov 30, 2018 — What Is Collimation? ... A laser collimator is a device that is used to narrow a beam of light. It can be used to arrange the beam of light in a ...

Y.Y.K. supervised the project. J.L. and M.J.K. conceived ideas for the project and performed the theoretical analysis. J.L. performed numerical simulations. J.L., M.J.K., W.L., and H.M.S. performed the experiments. J.L. and Y.Y.K. wrote the manuscript.

Kheybari, M., Daraio, C. & Bilal, O. R. Tunable auxetic metamaterials for simultaneous attenuation of airborne sound and elastic vibrations in all directions. Appl. Phys. Lett. 121, 081702 (2022).

Parra-Raad, J., Khalili, P. & Cegla, F. Shear waves with orthogonal polarisations for thickness measurement and crack detection using EMATs. NDT E Int. 111, 102212 (2020).

Designing microstructures of metamaterials that exhibit desired effective physical properties is challenging yet crucial. In this paper, we utilize unit cells shaped as rectangular parallelepipeds. These cells feature obliquely perforated cylindrical holes of varying sizes. This design is implemented to achieve the specific anisotropy described in Eqs. (3)–(6). The geometry of the unit cell is characterized by seven parameters, \({L}_{x},\,{L}_{y},\,{L}_{z},\,{r}_{1},\,{r}_{2},\,{r}_{3},\) and L, as shown in Fig. 2a. Symbols Lx, Ly, and Lz denote the unit cell dimensions in the x-, y-, and z-directions, respectively. The radii of the circular cross-sections of three different cylindrical holes are denoted by r1, r2, and r3. The holes are arranged at an interval of L in the x-direction, which is the wave propagation direction. Here, we note that the cylindrical holes are drilled in the direction perpendicular to the x-axis for the realization of C15=C16=0. In addition, the cylindrical holes are rotated by 45°, allowing the metamaterial to attain C55=C66. Most notably, the metamaterial can exhibit a non-zero C56 because the drilling direction is not parallel to the y- or z-axes. The C56 value can be tailored to satisfy the coupled resonance theory by adjusting the radii of the cylindrical holes constituting the metamaterial. For the realization of perfect elastic circular polarization in isotropic solids, the geometric parameters of the unit cell were optimized using a gradient-based algorithm28. In practice, an aluminum-based anisotropic metamaterial was designed to achieve the perfect SV-to-LCS polarization conversion in aluminum at 100 kHz. The optimization result of the geometric parameters is given in Supplementary Table 1. See Supplementary Note 5 and Supplementary Figs. 4 and 5 for the realization of other types of linear-to-circular polarization conversion (SV-to-RCS, SH-to-LCS, and SH-to-RCS).

Thus, with prime lenses, photographers on a budget have the chance to experience world-class optics at a fraction of a cost of those expensive variable focal length lenses, and there is no need to make compromises with cheap, lower quality zoom lenses all the time.

Thomas, R. L., Turner, G. & Bohm, H. V. Circularly polarized ultrasonic shear waves in metals. Phys. Rev. Lett. 20, 207 (1968).

Lakhtakia, A. Shear axial modes in a PCTSCM: Part V: transmission spectral holes. Sens. Actuator A Phys. 80, 216–223 (2000).

Lee, H. J. et al. Effective material parameter retrieval of anisotropic elastic metamaterials with inherent nonlocality. J. Appl. Phys. 120, 104902 (2016).

Modern zoom lenses often offer 3-4 stop image stabilization systems, be it Canon’s Image Stabilization (IS), Nikon’s Vibration Reduction (VR), Sigma’s Optical Stabilization (OS) or Tamron’s Vibration Compensation (VC). Even if you have an f/4 lens you can still get sharp images when shooting non-moving subjects in dark environments. Thanks to the image stabilization technology, your lens will make some of its internal optical elements move and shift to counter camera shake, which lets you use extremely slow shutter speeds.

I think the key factor which decide the price, size and weight not because of it’s a prime or a zoom, but really depends on the maximum aperture which decides the optical quality and performance of a lens.

Nov 28, 2013 — You have to know the pixels in order to get the pixels-per-inch conversion. For example, if you have a 100x100px image that you wanted to ...

This research was supported by the Global Frontier R&D Program on Center for Wave Energy Control based on Metamaterials (CAMM-2014M3A6B3063711) contracted through the Institute of Advanced Machines and Design at Seoul National University funded by the Korea Ministry of Science, ICT & Future Planning. This research was also supported by the National Research Foundation of Korea (NRF-2022R1A2C2008067) funded by the Korea Ministry of Science, ICT & Future Planning. J.L. acknowledges the Global PhD Fellowship (NRF-2019H1A2A1075829) funded by the Korean Ministry of Education.

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In recent years, zoom lenses have been taking over the hearts of many working professional photographers as the more obvious, versatile choice. With the latest image sensors producing amazing quality, even at extremely high ISOs, it makes sense why more people have been leaning towards the convenience of zoom lenses. Zoom lenses have also gotten impressively sharp – most, even some cheap kit lenses, are sharp enough for day-to-day needs and also boast effective image stabilization systems.

Here, we note that C11 does not affect the transmission and reflection of shear waves because of Eq. (4). The spatiotemporal displacement fields in Fig. 1b support that the linearly polarized input displacement vector is perfectly converted into the circularly polarized output displacement vector as an elastic wave propagates through the metamaterial that satisfies the theoretical conditions in Eqs. (3)–(6). A video demonstration of Fig. 1b can be found in Supplementary Movie 1.

Here, we propose a novel resonance mechanism for the generation of perfect circular polarization of elastic waves in isotropic solids. Our approach is to perfectly convert an incoming linearly polarized elastic wave through an anisotropic medium (realized by a metamaterial) into a circularly polarized elastic wave in the target isotropic solid. We show that the perfect conversion is possible if the anisotropic medium has effective material properties to exhibit a unique coupled resonance phenomenon at a target frequency; the resonance refers to the simultaneous occurrence of the Fabry-Pérot resonance in one diagonal plane and the quarter-wave resonance in another diagonal plane. It has been well known that a linearly polarized elastic wave can be fully transmitted to the target medium using either Fabry-Pérot resonance13 or quarter-wave resonance with impedance matching14. However, these two resonances are fundamentally different from the proposed coupled resonance in that either of the two resonances can realize the full transmission of any linearly polarized elastic wave but not the circularly polarized elastic wave. The coupled resonance for generating circularly polarized elastic waves induces these two resonances simultaneously within the anisotropic medium, resulting in the full transmission of two orthogonal linearly polarized elastic waves at the exact phase difference of 90°. We establish the theoretical conditions for the coupled Fabry-Pérot and quarter-wave resonances, which can be turned into the conditions for the effective material properties that the anisotropic medium must satisfy. Using the coupled resonance, it is possible to achieve perfect linear-to-circular polarization conversion without any theoretical limit, overcoming the intrinsic limitations of the classical birefringent plate.

Elastic waves involving mechanical particle motions of solid media can couple volumetric and shear deformations, making their manipulation more difficult than electromagnetic waves. Thereby, circularly polarized waves in the elastic regime have been little explored, unlike their counterparts in the electromagnetic regime, where their practical usage has been evidenced in various applications. Here, we explore generating perfect circular polarization of elastic waves in an isotropic solid medium. We devise a novel strategy for converting a linearly polarized wave into a circularly polarized wave by employing an anisotropic medium, which induces a so-far-unexplored coupled resonance phenomenon; it describes the simultaneous occurrence of the Fabry-Pérot resonance in one diagonal plane and the quarter-wave resonance in another diagonal plane orthogonal to the former with an exact 90° out-of-phase relation. We establish a theory explaining the involved physics and validate it numerically and experimentally. As a potential application of elastic circular polarization, we present simulation results demonstrating that a circularly polarized elastic wave can detect an arbitrarily oriented crack undetectable by a linearly polarized elastic wave.

Condition (3) is required to achieve the 90° out-of-phase relation between transmitted SV and SH waves in the isotropic background with the full (100%) energy efficiency of the polarization conversion. In order to accomplish this, our idea is comprehensively employing two distinct resonances for full transmission: Fabry-Pérot resonance and quarter-wave resonance with impedance matching. Fabry-Pérot and quarter-wave resonances are characterized in that the thickness of the metamaterial must be matched by the half-wavelength and quarter-wavelength of the wave propagating through the metamaterial. When the slow and fast eigenmodes inside the metamaterial are matched by half-wavelength (i.e., \(d={n}_{{{{{{\rm{SE}}}}}}}\cdot \frac{{\lambda }_{{{{{{\rm{SE}}}}}}}}{2}\) (nSE = 1,2,3…)) and quarter-wavelength (i.e., \(d={n}_{{{{{{\rm{FE}}}}}}}\cdot \frac{{\lambda }_{{{{{{\rm{FE}}}}}}}}{4}\) (nFE = 1,3,5…)), their 90° phase difference is always guaranteed because \(\varDelta {\phi }_{{{{{{\rm{SE}}}}}}}=\frac{2\pi }{{\lambda }_{{{{{{\rm{SE}}}}}}}}\cdot d={n}_{{{{{{\rm{SE}}}}}}}\cdot \pi\) and \(\varDelta {\phi }_{{{{{{\rm{FE}}}}}}}=\frac{2\pi }{{\lambda }_{{{{{{\rm{FE}}}}}}}}\cdot d=\frac{{n}_{{{{{{\rm{FE}}}}}}}\cdot \pi }{2}\). Here, \(\varDelta {\phi }_{{{{{{\rm{SE}}}}}}}\) and \(\varDelta {\phi }_{{{{{{\rm{FE}}}}}}}\) denote the phase changes of the slow and fast eigenmodes through the metamaterial, and λSE and λFE denote the wavelengths of the slow and fast eigenmodes inside the metamaterial. Importantly, the wavelengths of the slow and fast eigenmodes can be modulated by the SV-SH mode-coupling stiffness constant of the metamaterial as follows (see Supplementary Note 2 for derivation):

Frenzel, T. et al. Ultrasound experiments on acoustical activity in chiral mechanical metamaterials. Nat. Commun. 10, 3384 (2019).

To experimentally verify that the coupled resonance theory can generate perfect elastic circular polarization within isotropic solids, we fabricated the aluminum-based anisotropic metamaterial designed in Fig. 2 and conducted ultrasound experiments. Specifically, a super-drilling procedure was used to machine the 3 × 45 high-aspect-ratio cylindrical hole array in the center of the large-scale bulk aluminum specimen. Then, the specimen was rotated 45° about the x-axis, as shown in Fig. 3a, to allow the wave to pass through the obliquely perforated microstructures. Shear-wave ultrasound actuators, as shown in Fig. 3b, were utilized as the shear-wave transmitter and receiver. The incident wave was an SV wave with a 5-cycle sinusoidal waveform and a frequency of 100 kHz. To visualize the transmitted elastic circular polarization through the metamaterial, the temporal trajectory of the measured output shear-wave displacement was presented in Fig. 3c. The result shows that the circularly rotating trajectory was observed, and the radius of the measured trajectory was close to the radius of the theoretically calculated steady-state circular trajectory assuming full transmission. The differences between the theory and the experiment could be induced by the distorted plane-wave generation due to the finite size of the wave source and unavoidable wave reflections at the boundary of the specimen. Nevertheless, our experiments demonstrated that nearly perfect circular polarization of elastic waves in aluminum, a common and widely used isotropic solid, could be realized with the anisotropic metamaterial based on the coupled resonance theory.

Yang, X. & Kim, Y. Y. Asymptotic theory of bimodal quarter-wave impedance matching for full mode-converting transmission. Phys. Rev. B 98, 144110 (2018).

On the other hand, most professional-level zoom lenses will have a single maximum aperture throughout the zoom range. Here are some very popular zoom lenses for different camera mounts:

For numerical validation of the proposed metamaterial, finite element analysis-based simulations were conducted. The time-harmonic simulation result in Fig. 2b confirms that the metamaterial perfectly converts the incident SV wave into the LCS wave at the resonance frequency of 100 kHz. Quantitatively, the metamaterial produced highly accurate circular polarization with \(\frac{|{t}_{{{{{{\rm{SH}}}}}}}|}{|{t}_{{{{{{\rm{SV}}}}}}}|}=1.004\) and \(\frac{|\angle {t}_{{{{{{\rm{SV}}}}}}}-\angle {t}_{{{{{{\rm{SH}}}}}}}|}{0.5\pi }=0.998\), which should both be 1 for circular polarization to be exact. Moreover, nearly zero reflection can be found in Fig. 2b, indicating the nearly full transmission through the metamaterial. Indeed, the transmission and reflection coefficients of longitudinal waves were identically zero. The spatiotemporal displacement fields inside the proposed unit cell, presented in Fig. 2c, also support that incident linear polarization is converted into circular polarization as the wave passes through the metamaterial. A video demonstration of Fig. 2c is provided in Supplementary Movie 2. In addition, time-transient simulations were conducted to demonstrate the non-steady-state response of the proposed metamaterial, and the result in Fig. 2d validates that the transmitted LCS wave can be formed within three sinusoidal cycles of the incident SV wave. Moreover, the simulated time-transient circular particle motion was nearly identical to the theoretically calculated time-harmonic circular trajectory under the assumption of full transmission. A video demonstration of the time-transient simulation can be found in Supplementary Movie 3.

First of all I would like to thank you for the great information you gave, it’s very helpful for people how to select their lenses suitable for their needs.

A prime lens is a lens with a fixed focal length (also commonly referred to as a “fixed lens”). What this means is that such a lens has a set angle of view that can not be changed. The only way of enlarging your subject and making it fill more of the frame is by physically getting closer to it. In turn, the only way to fit more into the frame is to step back.

Buckmann, T. et al. An elasto-mechanical unfeelability cloak made of pentamode metamaterials. Nat. Commun. 5, 1–6 (2014).

Image stabilization is not just limited to zoom lenses. Some of the newer fixed focal length lenses also boast image stabilizer technologies, such as the newly announced Canon 35mm f/2 IS.

Yang, X., Kweun, M. & Kim, Y. Y. Monolayer metamaterial for full mode-converting transmission of elastic waves. Appl. Phys. Lett. 115, 071901 (2019).

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The following conclusions can be made as we investigated the so-far-unexplored circular polarization of elastic waves in common isotropic solids. We discovered that it is possible to perfectly generate a circularly polarized elastic wave by passing a linearly polarized elastic wave through an anisotropic elastic medium having specific physical properties. We derived the theoretical conditions required for the linear-to-circular polarization-converting medium realized by a metamaterial. In addition, the physics underpinning the perfect polarization conversion, the coupled resonance between Fabry-Pérot and quarter-wave resonances, was revealed. Our theory was confirmed through the ultrasonic wave experiment.

Miao, H. & Li, F. Shear horizontal wave transducers for structural health monitoring and nondestructive testing: a review. Ultrasonics 114, 106355 (2021).

A single zoom lens can replace two or three prime lenses. This also means that you only need to worry about moving around with a single attached lens. A single zoom lens might save you from carrying a large backpack. In a way, certain zoom lenses allow you to reduce weight, because you don’t need to bring several primes to cover the whole range. Less lens swapping also means cleaner sensor and optical elements.

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

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Nature Communications thanks the anonymous reviewers for their contribution to the peer review of this work. A peer review file is available.

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Jul 5, 2022 — You use an ND filter when you want to take a shot with specific settings, but the light is too strong for the settings you wish to use and ...

It takes time to realize which gear suits your style of shooting better. Some people end up with a single “do it all” superzoom lens, while others swear by their prime lenses and refuse to ever touch a zoom lens. As you learn how to use your gear overtime and start ironing out your photography skills, it really does not matter what you pick, as long as it does not stop your creativity.

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Some of the modern pro-grade lenses offer image quality that matches or even surpasses primes lenses in the same focal range. Despite all this, prime lenses haven’t really lost their desirability. Sony, Nikon, and Canon have been rapidly updating and expanding their lens arsenal with new and better choices. Third-party manufacturers like Sigma and Tamron are stepping into the game with confidence.

I partially agree with this and I can say that my 50mm prime has helped me in some regards, but in all honesty, such a restraint can be equally damaging to your learning process. I believe it is important to have at least one zoom lens if you are a prime shooter, and vice versa.

First of all ,I do events photography the lens that I used most is a zoom 28-200 , plus a powerful on camera flash.Todays camera flash has e-TTL, this way you always get the correct exposure. Even if you used a prime lens , you always cannot control the source of light , so some shot taken taken even with the best primes , is over exposed or under exposed. What Im saying is that even with the most expensive prime lens, or the most expensive equipment, its the skill of the photographer that really matters.

Lastly, do keep in mind that image stabilization can be present on lenses or camera bodies. Most mirrorless cameras and Pentax DSLRs have in-body image stabilization (IBIS), although for longer focal lengths, lens stabilization is still superior.

As a homogenization method of the designed 3D anisotropic metamaterial, we find effective physical properties with the same magnitude and phase of scattering parameters as those calculated from the metamaterial29. The entire metamaterial is treated as having homogenized effective physical properties30,31. Transmission coefficients of the designed metamaterial were numerically calculated as \({t}_{{{{{{\rm{L}}}}}}}=0\), \({t}_{{{{{{\rm{SV}}}}}}}=0.0527+0.7016i\) and \({t}_{{{{{{\rm{SH}}}}}}}=-0.6988+0.0551i\). Reflection coefficients were calculated as \({r}_{{{{{{\rm{L}}}}}}}=0\), \({r}_{{{{{{\rm{SV}}}}}}}=0.0180+0.0038i\), and \({r}_{{{{{{\rm{SH}}}}}}}=-0.1023-0.0519i\). The retrieved effective density and stiffness constants of the designed metamaterial are \(\rho=3024\,{{{{{{\rm{kg}}}}}}}\,{{{{{\rm{m}}}}}}^{-3}\), \({C}_{55}={C}_{66}=16.6\,{{{{{\rm{GPa}}}}}}\), and \({C}_{56}=-4.7\,{{{{{\rm{GPa}}}}}}\). Indeed, the effective physical properties of the metamaterial satisfy the theoretical values (exhibiting the coupled resonance with \({n}_{{{{{{\rm{SE}}}}}}}=2\) and \({n}_{{{{{{\rm{FE}}}}}}}=3\)) obtained by Eqs. (3)–(6) within the numerical error of 5%.

Crampin, S. & Chastin, S. A review of shear wave splitting in the crack-critical crust. Geophys. J. Int. 155, 221–240 (2003).

This is sometimes also true with cheaper zoom lenses that go very wide, which sometimes are weaker at their widest focal length.

Lee, J. et al. Perfect transmission of elastic waves obliquely incident at solid-solid interfaces. Extreme Mech. Lett. 51, 101606 (2022).

And some lenses like true macro lenses are only available as primes! So, whether you get a prime or a zoom depends on your application. Although zooms produce amazing images and are versatile, there’s simply no substitute for owning a high-quality fast prime!

2022623 — The diffraction grating sheet is reusable. I've printed on it numerous times. As long as you don't fuse to it, you can just keep using it!

Prime lenses offer something of a compromise – they trade versatility in favor of size and weight. A while ago, I decided to go with a 85mm f/1.4 lens instead of a 70-200 f/2.8 and never really regretted this decision. Having only big lenses may sometimes mean you will leave your camera at home instead of taking it with you wherever you go.

The most obvious reason for buying zoom lenses is their versatility. Zoom lenses can be great when a photographer needs to be sure he can handle a variety of different situations: you can go from wide-angle to telephoto in a quick turn of the zoom ring without the need to physically move. Landscape and wildlife photographers, for example, are often limited to a particular spot or area, so being able to zoom to an area of interest can be invaluable for properly framing a shot.

where C11, C55, and C66 correspond to the stiffness constants of L, SV, and SH waves, respectively, while C15, C16, and C56 correspond to the mode-coupling stiffness constants between L-SV, L-SH, and SV-SH waves, respectively. All mode-coupling stiffness constants are always zero in isotropic solids, but they can be non-zero in anisotropic metamaterials.

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PL provides various digital photography news, reviews, articles, tips, tutorials and guides to photographers of all levels

Nasim Mansurov is the author and founder of Photography Life, based out of Denver, Colorado. He is recognized as one of the leading educators in the photography industry, conducting workshops, producing educational videos and frequently writing content for Photography Life. You can follow him on Instagram and Facebook. Read more about Nasim here.

Kweun, J. M. et al. Transmodal Fabry-Perot resonance: theory and realization with elastic metamaterials. Phys. Rev. Lett. 118, 205901 (2017).

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Cushing, C. W. et al. Design and characterization of a three-dimensional anisotropic additively manufactured pentamode material. J. Acoust. Soc. Am. 151, 168 (2022).

Now that you’ve seen the advantages of each type of lens, which kind should you get? It all depends! If you’re going after very shallow depth of field, a prime lens would be ideal. That’s especially true on smaller sensor cameras such as micro four thirds cameras, where depth of field is not as shallow as with full-frame cameras at the same apertures, assuming that the focal length and field of view are the same.

In Fig. 1, to calculate the scattering parameters of a 3D anisotropic metamaterial sandwiched by an isotropic background medium, we construct the 6 × 6 scattering matrix for the case of the SV wave incidence as

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Let’s talk some true fact: the wieight of one 24-70 f2. 8 zoom is much more lighter than the total weight of the 24mm, 35mm, 50mm and 70mm when take them all to caver the same focal length, and the price of these four primes, say not so fast just take f1.8 will overpass the price of 2470f2.8. Therefore it’s not always true that zoom lens is much more expensive nor weighs much more than the primes for the same range of focal length.

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a The unit cell of the 3D anisotropic metamaterial with three different-sized holes. b The time-harmonic numerical simulation result with the designed unit cell. The unit cell is made of aluminum and inserted between aluminum (periodic conditions in the y- and z-directions). The SV wave is incident on the unit cell in the x-direction at 100 kHz. c The spatiotemporal displacement field inside the designed unit cell at the resonance frequency. \({{{{{{\bf{u}}}}}}}_{x=0}\) and \({{{{{{\bf{u}}}}}}}_{x=d}\) represent the displacement vector at the incident and transmission interfaces of the designed unit cell, respectively, and k represents the wave propagation direction. d The time-transient numerical simulation result with the designed unit cell. The output y- and z-displacements through the metamaterial are presented with the theoretical steady-state displacement trajectory (magenta) assuming full transmission. e Simulated transmission spectra of the designed unit cell (blue) with the theoretical transmission spectra (red) exhibiting the coupled resonance with \({n}_{{{{{{\rm{SE}}}}}}}=2\) and \({n}_{{{{{{\rm{FE}}}}}}}=3\). The magnitudes of the transmitted SV and SH waves are presented on the left and middle, and their phase difference is presented on the right.

In this section, we derive the theoretical conditions that the physical properties of the anisotropic metamaterial should satisfy for perfect linear-to-circular polarization conversion. The incident wave can be either an SV or SH wave, and the transmitted wave can be either a left-handed circularly polarized shear (“LCS”) or a right-handed circularly polarized shear (“RCS”) wave. In Fig. 1, without loss of generality, we consider the case of SV-to-LCS polarization conversion. Inside the anisotropic metamaterial, the stress field (\({[{\sigma }_{xx}\,{\sigma }_{xz}\,{\sigma }_{xy}]}^{{{{{{\rm{T}}}}}}}\)) and the strain field (\({[{\varepsilon }_{xx}\,{\gamma }_{xz}\,{\gamma }_{xy}]}^{{{{{{\rm{T}}}}}}}\)) are related as

These days, both zoom and prime lenses are fairly sharp. But for longer focal lengths, zoom lenses tend to lose sharpness near their maximum focal length. This is especially true with lenses that go up to 500mm or 600mm, where prime lenses in this category always outdo zoom lenses.

Zoom lenses have two specifications that represent the two extremes of the zoom range, like 70-200mm. Such a lens may act as a 70mm focal length lens, a 200mm focal length lens and everything in-between. In addition, zoom lenses could also have variable aperture ranges.

Many modern prime lenses are significantly cheaper than their zoom counterparts. A 24mm f/2.8 lens will set you back around $400, while a 24-70mm f/2.8 will cost $1900-2300. Even if you cover focal lengths between 24mm and 70mm with fast primes like 35mm f/1.8, 50mm f/1.8 and 85mm f/1.8, you will still end up paying less.