Nikon Shift happens in SLR world too

mike3996

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So out of curiosity I read a couple of Nikkor lens reviews. Focus shift was mentioned.

What's the exact way one is supposed to go about it shooting a (D)SLR? After all, focus happens wide open and then it closes for exposing.

Does one just hold the aperture preview button while (auto)focusing? Isn't that pretty cumbersome, not to mention doing this with tight apertures.

I always thought that rangefinder people can just about tolerate this but, I thought, in SLR lenses it would be a design priority to avoid focus shift! Now if that's not the case, wow.

My theory is that SLR shooters are accustomed to getting soft images (the lenses, they certainly aren't Leica) not to mention substandard focusing methods. ;)
 

mike3996

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Location
Finland
This is particularly weird, a DPR reader describes:

1: Set lens to MF and focus, using live view, on something with the lens wide open. Take a series of shots at f/1.8, f.2.8, f/4 & f/5.6 without refocusing. In the series of shots, it is easy to see the "plane" of focus shifting away from the camera as the aperture closes down.

2: Make the same series of shots but this time, use phase detect AF and allow the camera to refocus for each shot. The apparent plane of focus in the images stays pretty much the same through the series.

Is it possible that the cameras do actually compensate for shift in those lenses that support it?
 

Someone has already scanned the article I have in hardcopy. 1977 Pop Photo test of 32 normal lenses.

My Nikkor 55/1.2 shows 0.03mm focus shift from F1.2 to F4. The Elmar 50/2.8 shows 0.11mm from F2.8 to F8, the Summicron 0.05mm from F2 to F8.

In general the SLR lenses have less due to the longer flange distance, meaning a longer light path.

No one worried about a 0.03mm focus shift from F1.2 to F4, the DOF more than covers it. With digital pixel peeping, you might be able to see it. Use live-view with the lens stopped down to taking aperture if it is super-critical.
 

mike3996

Hall of Famer
Location
Finland
Those amounts of shift are fine indeed. Hell, can a human even consistently hit his focus within 0.03 mm tolerance, if shooting handheld? No way. :)

And to be fair I think my Summicron-M 35mm ASPH shifts more than that.

Edit: removed a bit about shift on a 28/1.8G that was probably incorrectly remembered.
 

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