so a friend came over with his new A1mk2 and his a7r5 and i set them up on my extreme macro setup. the a1mk2 did not experience any diffraction at all.
the images were super sharp and very detailed. the a7r5 showed diffraction on both my 4x and 10x objectives, in fact those 60 megapixels could not out resolve my 33 meg a7iv ,and i was viewing the spider at up to 1000% 🤨where the a7iv had super sharp detail and pixelated, the a7r5 was blurry but was not pixelated. a studio full body shot with my 28 75 2.8 tamron set to f3.5 totally different storey ,it could out resolve my a7iv but only after 300% viewing. but the DR on the a7iv was better, not buy much and not something that couldnt be fixed in PS anyway.
June 4, 2025
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The Z105 becomes a 73mm at 1:1 thanks to focus breathing.
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So by convention and assuming that (105/22) mm is the minimum aperture size, that would be 73 x 22 /105 = effectively about f/16.
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And I wouldn't call diffraction a problem, per se - since every capture has some diffraction in the image plane, whether it appears in the print / on-screen or not.
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I discovered the problem with the a7r5, it wasnt diffraction, it was slow sensor speed at 100ms using my extreme macro studio, the reason the a1mk2 was so sharp is the sensor speed is 8ms as im using electronic shutter with no black put viewing.
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Thanks - my faith in optical physics is restored ... 😀
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had me questioning as well. i knew my a6700 had some very minimal diffraction at 10x but couldnt figure out why the A1mk2 was so sharp even at 50 mpixels compared to the a7r5 at 60. i can also say that 8.5 stops of IBIS is total marketing crap, because it was no better than my 5.5 stop 7iv.
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for anyone interested in the physics of diffraction, an interesting thing to observe is how the shadow of a building is not a sharp transition between sun and shade but that there is a narrow grey diffraction-induced zone between, This is the same effect that occurs between the edges of the aperture (or any border meeting the light while in transition in the lens, (hence the importance of large apertures for resolution)) With bellows or distance rings the recording medium is farther away and this will make the effect more visible since the rays/particles continue on their presumably linear path .
p
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Good point ...
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Illusion, exacerbated by upsampling methods that create pixelation (Nearest Neighbor and variants/hybrids). Instead of looking at how "sharp" details are on an insect, try both sensors with the same lens on text of variable size, like a document that scales font size by 0.8x with each subsequent line of text, printed and photographed from a distance. I don't even need to do this to know the outcome - there 60MP will record more lines, legibly, while the 33MP will give sharper results that are illegible gobbly-gook.
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not into black and white writing as accurate testing.
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60 meg greater cropability right 🤔🫣
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I have a Sigma 50mm macro that goes "up" to f/45 and, at that setting, diffraction is noticeable and can be a problem with some subjects.
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In case anyone doesn't get it, my lens at f/45 would give a blur diameter of about 14 image pixels at 4.3 um pixel pitch.
In answer to the OP, that is a "real problem".
pixel blur diameter = (Airy disk diameter)/(pixel pitch).
That 14px blur diameter can be simulated to an extent by applying a 14/4.3=2.5 px Gaussian blur to an image shot with say a late-model Canon APS-C camera.
For Alan's f/22 the pixel blur width is about 7px or a Gaussian blur of 1.22; Well noticeable to sharpness freaks, I'd say.
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Interesting, Nigel, what lenses do you own that have smaller aperture diameters than f/45?
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Never mind, Nigel ... forget the question.
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I wonder what the thinking is with manufacturer limits. It could be "what if the user uses f/128 by accident and all their images are under-exposed?". Also, it could be the difficulty of obtaining accuracy and consistency in aperture size and shape as it gets very small, affecting exposure consistency. We don't normally think of "bokeh" with very small apertures, but if you do "macro" with a very small aperture very close to the subject, distant points of light In the background might still form bokeh "balls" large enough to appear distorted.
In the witness of real world products, minimum apertures seem to be correlated to literal aperture diameters, not f-numbers, unlike maximum apertures, which correlate more with the f-number (lenses "faster" than f/1.4 are rare).
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Agreed, John. With a normal diaphragm at minimum diameter, there has to be a point where the tolerance of the actual diameter^2 is outside acceptable limits of exposure/diffraction variance.
