Re: Official: Fujifilm GFX 50S Medium Format Announced!
Jman13 wrote:
People need to stop conflating softening due to diffraction and softening due to lens design at smaller apertures. They may have the same effect on the image, but they do not have the same cause. A lens with an aperture at f/11 causes the same amount of diffraction as any other lens at f/11. The amount of diffraction is based on the focal length, physical aperture size and wavelength of light. In the equation to describe the airy disk, the relationship between focal length and physical aperture size is f/d, which is also the definition for f-stop. So the amount of diffraction in a projected image is SOLELY based on f-stop and wavelength of light.
Other image degradation, that may happen due to lens design, may also happen at less than optimal apetures. (Most lens designs aren\'t as good at f/16 as they are at f/8, just like they aren\'t quite as good in most cases at f/1.4 as they are at f/5.6). You will see additional softening due to this as well, but it isn\'t due to diffraction. Diffraction limiting is something that is very easily calculated by simple equations about the known properties of light.
This is a major source of confusion because most discussions/article/reviews seem to label ALL image degradation as the lens stops down as diffraction. Then we end up with *two* working definitions of diffraction which can make discussing the subject very difficult
Sep 21, 2016 at 08:48 AM
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