Born in 1959 in Yamanashi. After graduating from Nihon University, Hagihara was involved in the launch of the photography magazine Fukei Shashin where he worked as an editor and a publisher. He later resigned and became a freelance photographer. Currently, Hagihara is engaged in photography and written works centring on natural landscapes. He is a member of the Society of Scientific Photography (SSP).

Focal length

r(Airy) is the Airy radius, λ is the wavelength of the illuminating light, and NA(Obj) is the objective´s numerical aperture (objective aperture = condenser aperture). The numerical aperture depends on the aperture angle of the illumination entering the objective aperture, as well as the refractive index of the imaging medium:

Minimumfocus distance

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The image formed by a perfect, aberration-free objective lens at the intermediate image plane of a microscope is a diffraction pattern with a very specific intensity distribution. This tutorial explores the effects of the objective´s numerical aperture (NA) on the diffraction pattern and the resolution of a microscope. The three-dimensional representation of the diffraction pattern is the Point-Spread-Function (PSF) which, in a coma- and/or astigmatism-free system, is symmetrically periodic both along the optical axis, and radially across the image plane. This diffraction pattern can be sectioned in the focal plane to produce a two-dimensional diffraction pattern, having a bright circular disk surrounded by an alternating series of bright and dark higher-order diffraction rings whose intensity decreases with distance from the central disk, the so-called Airy disk. Under visual microscopical observation, only two or three of the circular luminous rings are usually visible in the intermediate image plane.

Learn the best ways to create amazing images and videos, share your works with the community and be inspired by our community.

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By satisfying several conditions, a large bokeh can be obtained even with a standard zoom lens. Find out more as I explain how to do so with the help of some photos of flowers. (Photo & text by: Kazuo Nakahara)

The tutorial starts with a pattern of Airy disks appearing in the focal plane of the microscope and the point-spread function / three dimensional of a corresponding, single Airy disk pattern shown on the right. To operate the tutorial, use the Numerical Aperture slider to change the objective´s numerical aperture and the resolution of the Airy patterns. The left position of the slider shows the pattern at the lowest objective numerical aperture (= 0.20), and the right position illustrates the highest degree of resolution (numerical aperture = 1.30). As the slider is moved from left to right, the objective’s numerical aperture increases and the complex Airy pattern, as visible in the image, results in a progressively increased resolution of image detail. Correspondingly, the central peak and higher-order diffraction rings in the three-dimensional Airy pattern drawing grow smaller in diameter.

- When you shoot macro On many macro lenses, you usually have to be at the closest focusing distance to achieve the maximum magnification. But you don’t always want to be too near your subject, especially if you are shooting sensitive creatures such as insects.  Tip: Use a a telephoto macro lens like the EF180mm f/3.5L Macro USM (C.F.D: 0.45m) or the EF100mm f/2.8L Macro IS USM (C.F.D: 0.3m) to achieve life-size magnification even when shooting from some distance away.

This series is all about answering questions regarding lenses that you thought you knew but didn’t. In this article, we look at one lens specification that you might want to consider when you buy lenses or choose which one to use: The closest focusing distance, also known as the minimum shooting distance. (Reported by: Shirou Hagihara, Digital Camera Magazine)

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Know this: Compact cameras may carry specifications such as “1cm macro”. This refers to the working distance of the lens, not the closest focusing distance.

Focus distance

Many people think that the closest focusing distance and the working distance of a lens are the same thing. They are related concepts, but they are not the same!

A lens that has a very short closest focusing distance allows you to achieve sharp, in-focus images with a shorter working distance.

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Tip: There are pitfalls to shooting too close It’s great to have the freedom to be able to shoot close to your subject, but too close and the lens hood and lens shadow might be captured in your shot—not ideal for some shooting scenes! Take the necessary precautions. If your lens doesn't have built-in Macro Lites, consider if you want to invest in a flash that is designed for macro photography.

Canon EOS cameras have a focal plane mark on the camera body. The image sensor is located under this mark. The focusing distance is measured from this mark to the subject. If the lens has a distance scale, the shortest distance indicated on the scale is equivalent to the closest focusing distance.

The closest focusing distance of a lens (see A below) refers to the shortest distance that must be between your subject and the surface of the image sensor (the focal plane) for the lens to focus. It is not affected by the length of your length, and does not change even if you zoom your lens.

Resolution is clearly influenced by the objective’s numerical aperture. Note that lower values of D indicate higher resolution. In the tutorial, the Numerical Aperture slider is used to control how the image structure evolves as the objective’s numerical aperture is increased. At the lowest numerical aperture value (0.20), the image details visible in the microscope are poorly defined and surrounded by diffraction fringes. As the slider is moved to higher numerical aperture values (0.50-0.80), the structural outline of the image becomes sharper and higher-order diffraction rings begin to emerge. At the highest numerical apertures (1.00-1.30), the diffraction disks are resolved individually as discrete luminous points surrounded by alternating series of bright and dark higher-order diffraction rings of decreasing intensity.

θ is the objective’s angular aperture and n is the refractive index of the medium (air, water, or oil) between the objective and the specimen.

Other than brightness, what sets an f/2.8 lens apart from an f/4 lens? Using the EF70-200mm f/2.8L IS II USM and the EF70-200mm f/4L IS USM, I will show how the two differ by comparing the apparent resolution and bokeh size. (Photos by: Ryosuke Takahashi)

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Unravel the “secret code” in a lens name, and find out about the story behind the red rings and white bodies on some lenses.

This foundational knowledge article explores the effects of the numerical aperture (NA) of an objective lens on the resolution of images produced by a microscope. It explains the diffraction pattern produced by an objective lens and how increasing the NA results in higher resolution images. The tutorial demonstrates the changes in image structure as the NA is adjusted.

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The resolving power of an objective determines the size of the formed Airy diffraction pattern: The radius of the central disk is determined by the combined numerical apertures of the objective and condenser. When condenser and objective have equivalent numerical apertures or the objective acts also as the condenser like in an inverted fluorescence microscope, the Airy pattern radius from the central peak to the first minimum is given by the equation:

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- When you are shooting in a tight space If the closest focusing distance is big, you will have to stand further away to focus on your subject. Framing and composition aside, this is also why it would be hard to use a telephoto zoom lens like the EF70-200mm f/4L IS II USM (C.F.D: 1.0m) to photograph someone sitting right across the table from you in a small, cozy café.

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- When you are trying to create bokeh Shooting with the camera closer to the subject results in a shallower depth-of-field, which helps to create a stronger background bokeh effect.

Capturing beautiful bokeh circles is one of the photography techniques that I would recommend trying. Once you have mastered the trick to creating them, you’ll be able to capture such photos effortlessly. Here, I will explain bokeh circles are formed as well as a few tips to capturing them. (Reported by: Kazuo Nakahara)

In contrast, the working distance (see B below) refers to the distance between the front end of the lens and the subject.