Does diffraction in a camera lens happen at a universal aperture in most or all lenses, or does it happen as a percentage of the maximum ap-?
erture?
2020-02-11T07:13:57Z
What I meant by universal aperture is that any lens by any brand that at f/32 is going to have the same amount of diffraction (as a % of image size), or if a lens that is capable of f/64 will have less diffraction at f/32 because it is capable of a smaller opening. It is commonly (perhaps not universally) said that around f/8-f11 the sharpness is best. I wanted to find out if a lens (if there is one) capable of f/64 will have the best sharpness around f/32, like an f/22 is sharpest around f/11.
Andrew Smith2019-10-06T10:51:51Z
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As sin( theta) = n lambda / d the smaller the value of d the greater the angle of diffraction. So a small aperture leads to greater diffraction "fuzziness". You should know that a small aperture is a large "f stop" ie f 16 or f 32
A pinhole camera has a less clear image than a larger lens.
So it has nothing to do with the smallest possible aperture. It is determined by the aperture actually used in any particular photo.
However the blurriness as a percentage of the image size is the same for all cameras using the same f ratio.
In practice, there is always some diffraction. Diffraction will only be 0 (no effective diffraction) when incoming light hits the interface/surface perpendicular to the plane of contact. Otherwise, some diffraction will occur. The smaller the aperture allowing in light to the lens, the more the light will be collimated (all moving parallel, in the same "line"), so diffraction will be reduced. Even the light that does hit non-perpendicular to the interface in that case will still be almost perpendicular because the closed aperture limits the area of light which can enter and still contact the lens.
There is always some chromatic aberration as well, which is what happens when light of different wavelengths diffracts at slightly different angles (prism effect).
In effect, unless you have light that is all moving in the same direction (all paths are parallel) and all the interface with the lens or whatever is perpendicular to that track, there will be diffraction. Wave behavior of light requires it.
Diffraction happens in the lens. Smaller aperture equates to a longer F/D ratio, less light getting through. The good- greater depth of field. The bad- more effect of coma and chroma aberration. Don't confuse lens diameter with aperture. You will have to define 'universal aperture' I don't know it.