There’s a reason the term “kit lens” has achieved a negative connotation. Most companies, Fujifilm not among them, don’t endeavor to make a great kit lens. I’m not going to name any names, but I have spoken to camera companies about kit lenses before, and responses consistently touch on two primary concerns. How can a company make a good and affordable lens? This is a tough problem to solve, and it is made more challenging by the second concern: how do you make a kit lens that is good enough to deliver a positive experience but not so good that someone won’t want to purchase additional lenses?

Because no material is 100% reflective, absolute efficiency measurements will always yield a lower numerical efficiency value than a relative efficiency measurement on the same grating. Grating efficiency for a given wavelength and groove spacing is strictly a function of the groove shape and the reflectance of the coating. The optimum groove shape is then a function of the angle of incidence and order of use.

What is gratingin physics

Gold (Au) – Superior performance over aluminum in the NIR region. Below 600nm the reflectance of gold falls off significantly and is a poor choice. Above 1200nm, gold offers very little advantage for a single pass application.

Quality vs. Function Here is where subjectivity comes into play. Everyone will have a different definition of quality. Some will include appearance, some will include only function, and some will include a combination of function/appearance/consistency relative to cost. When a universal definition is adopted, there will be no more debate on this matter. Until then, the debate continues.

What is gratingelement

Pinholes – Pinholes in a reflection grating serve only to reduce the total amount of light available for diffraction by the ratio of their area to the total area illuminated. This is insignificant. Any light passing through a pinhole in the coating is automatically rejected from the optical path of the system.

How dodiffractiongratings work

All of Optometrics’ gratings are marked on one edge with a blaze arrow. The figure below shows a typical arrow, and its relation to the blaze angle of the grating. For best efficiency, the arrow should be oriented such that the tip of the arrow points towards the source, inscribing the smallest angle possible, as shown.

What is gratingconstant

If you get a photographer in the door and ensure they have a great time, they will stick around. And if they stick around, they will inevitably purchase more lenses (and cameras) over the years, as they run into situations that can only be solved with different lenses. Not necessarily better, but different.

The master gratings are produced by forming the surface of a soft metallic coating with a diamond form tool. The resulting groove profile has a well defined and controllable groove profile that directs energy efficiently into the desired wavelength range.

A diffraction grating is a passive optical component that redirects light incident upon the surface at an angle that is unique for every wavelength in a given order. This redirection (or diffraction) is a result of the phase change of the electromagnetic wave as it encounters the regular, fixed structure of the grating surface. Every wavelength undergoes a different phase shift, and as a result, diffracts at a different angle, resulting in a dispersion of broadband light.

Most holographic grating masters are generated initially with a symmetric groove profile. It is important to note that a symmetric profile holographic diffraction grating will only have symmetry in efficiency on either side of zero order when the light is incident at 0 degrees (normal incidence). This explains why some symmetric holographic gratings can achieve greater than 50% absolute efficiency in a given order, although most do not. Special techniques can be employed to give some holographic gratings an asymmetric profile, and hence, blaze properties. These gratings combine the beneficial low stray light properties of holographic grating with the high efficiency of ruled gratings.

Of all of the topics that can be discussed relating to a diffraction grating, visual appearance is probably the most subjective, misunderstood, and maligned property one can think of. The reasons are understandable. When someone looks at a grating and sees what appears to be a flaw, the natural impulse is to imply a negative affect on performance. This may or may not be the case in theory, but is hardly ever the case in practice. A grating’s visual appearance, unless obviously grossly damaged, should never be used to assess its functionality.

While many kit lenses are stopgap measures, something you have to take decent photos while you learn how to use your camera and save money for an upgrade, that is not what the XF 18-55mm f/2.8-4 is. It is not a temporary solution waiting to be replaced. It is an entirely suitable long-term standard zoom lens. Sure, photographers may have wanted something a bit wider, longer, or faster for different types of photos, but that “24-70mm” range (27-83mm, in this case) was suitably covered.

What is grating

Dispersion is the ability of a grating to angularly separate adjacent wavelengths of light. The higher the separation, the higher the dispersion.

What is theorder ofdiffraction

Holographic master gratings generally exhibit better stray light properties than ruled master gratings. Blazing is not as easy with holographic gratings however, and with certain notable exceptions, they will not be as efficient as ruled, blazed gratings.

Protected Aluminum (Al) – Aluminum coat with a thin overcoat of magnesium flouride (MgF2) which prevents the formation of aluminum oxide which is absorbing in deep UV. It provides no benefit over bare aluminum for gratings used in VIS and IR.

While the immediate benefit of a good kit lens is obvious when it comes to saving money, the initial feeling of using it is much more important. A good lens shapes the entire experience of using a new camera. It cannot be overstated how essential a budding photographer’s initial experience is to their long-term interest in the craft (and a specific brand). And little harms that experience more than a lousy kit lens.

As the angle of diffraction approaches 90 degrees, the angular dispersion increases. Decreasing the groove spacing, increasing the angle of incidence and operating in higher orders are all effective ways to increase dispersion. Any set of conditions allowable by the grating equation that increases the angle of diffraction will increase angular dispersion.

Holographic master gratings are produced by exposing a thin layer of photoresist to 2 intersecting coherent, monochromatic beams. The resulting interference pattern differentially exposes the photoresist. After development, the sinusoidal variation in light intensity during exposure is transformed into a physical structure of the same profile. The addition of a reflective overcoat completes the process.

For best efficiency, the arrow should be oriented so that the tip points back towards the source, inscribing the smallest angle possible, as shown below.

While photographers can still get their hands on the Fujinon XF 18-55mm f/2.8-4 R LM OIS lens, it will no longer be the kit lens of choice for Fujifilm cameras, including for the new Fujifilm X-T50 camera. Supplanted by the new XF 16-50mm f/2.8-4.8 R LM WR, the XF 18-55mm f/2.8-4 proved challenging for competitors to match — not for a lack of ability, but a lack of desire.

The grooves of a ruled grating have a saw tooth profile with one side longer than the other. The angle made by a groove’s longer side and the plane of the grating is the “blaze angle.” The blaze angle for a blazed grating is generally the biggest factor in determining where the efficiency curve peaks under a certain set of conditions.

Digs – Digs are characterized as regular or irregular inclusions in or on the surface of the grating. They can be resident on the master grating, or introduced during the replication or coating process.

The efficiency of a grating in polarized light is dependent on the orientation of the plane of polarization relative to the direction of the grooves. For maximum efficiency, the grating should be oriented such that plane of polarization is oriented perpendicular (s-polarization) to the length of the grooves.

Ruled blazed gratings are very efficient, and are generally the best choice for applications requiring high signal strength. Because of the mechanical nature of the mastering process however, there can be random and periodic spacing errors that could detract from the purity of the diffracted spectra.

It may sound hyperbolic, but the XF 18-55mm f/2.8-4 is the most important Fujifilm X Series lens ever made. It has been the “first impression” lens for many photographers purchasing their first Fujifilm X Series camera and, in many cases, their first interchangeable lens camera.

Fujifilm focused on that first problem with the XF 18-55mm f/2.8-4 and ignored the second one entirely in favor of answering a third question. “How do we make a lens that makes new users excited to stay in the Fujifilm family?”

n = the order of diffractionλ = wavelength of lightd = distance between adjacent groovesi = angle of incidence with respect to grating normali’ = angle of diffraction with respect to grating normal

The Fujifilm XF 18-55mm f/2.8-4 R LM OIS has been around for a long time. It was announced in September 2012 alongside another great Fujifilm X Series lens, the XF 14mm f/2.8 R. The XF 18-55mm f/2.8-4 has long been a kit lens option for many of Fujifilm’s mid- and high-range cameras, a sort of “upgrade” option over the company’s XC 16-50mm f/3.5-5.6 OIS and later XC 15-45mm f/3.5-5.6 OIS PZ lenses.

When a master ruled grating is generated, the diamond tool does not actually remove material and cut a theoretically shaped groove. Rather, the coating is burnished by the tool. As a result, there is some displacement and deformation of the material on the short facet into the previously ruled groove every time a new groove is formed. The resulting profile will show some peak round-off, and not achieve theoretical depth. Actual groove depth is typically 90% of theoretical.

No, the XF 18-55mm is far from Fujifilm’s best X Series lens, although it is undoubtedly a great standard zoom lens and certainly one of the most-owned XF lenses. But it matters so much because of what it provides to new shooters.

What is the diffraction gratingin physics

Fujifilm took a long-term view with its legendary kit lens, and it paid significant dividends. While other manufacturers were thinking of ways to sell more lenses as quickly as possible — a reasonable approach, by the way — Fujifilm focused on using its camera kits to build positive, lasting relationships with photographers.

Scratches – Scratches are characterized in the conventional sense, deformation lines running in any direction other than the direction of the grating grooves.

Diffraction gratingformula

Ruling Glitches – Ruling glitches appear to be scratches that are perfectly straight and perfectly parallel to the groove direction. They appear only on ruled gratings, and are an artifact of the ruling process. During the ruling operation of the master grating, a small bit of the aluminum coating on the master blank will occasionally seize onto the diamond stylus and deform a few grooves before clearing itself from the tool. The deformed grooves are parallel all others, and are ruled at the same pitch as all others. If the deformed grooves are extremely ragged, it can be argued that they could degrade stray light performance, but their most likely affect is to simply redefine the blaze properties for those few grooves. Ruling glitches are not considered to be functional defects unless extremely excessive in quantity.

The simple fact of the matter is that, except in extreme cases, the performance of a diffraction grating is primarily a function of the things that you cannot see with the naked eye. The grating efficiency is a function of the shape of the groove and the reflectance of the coating. You cannot evaluate this with the naked eye. The stray light performance is primarily a function of the micro, not macro, structure of the grating surface. You cannot see a rough groove structure, or nonspecular reflective surface with the naked eye, but it’s easy to see a small dig or light scratch.

Absolute grating efficiency is defined as the percentage of monochromatic light diffracted in a given order compared to all of the monochromatic light incident on the grating.

This bold direction proved fruitful, and hopefully, the new XF 16-50mm f/2.8-4.8 kit lens will be as good at forging powerful, lasting bonds with new photographers as its predecessor, the lens no one else dared to make.

Relative grating efficiency is defined as the percentage of monochromatic diffracted light in a given order compared to the reflectance of the monochromatic incident light from a mirror coated with the same material.