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05-27-2014, 07:48 AM   #1
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Trust focus confirm or my eyes?

Today I was shooting a roll of Velvia 100F on the 645N and particularly when using the A-series 300/4 ED focused on far away subjects I got the distinct impression that when the focus confirm indicator lit up things didn't look their sharpest. It was a very small adjustment but it consistently felt like the subject looked sharper to my eye when I moved the focus point just a tiny bit closer. It was landscape work so I was mostly shooting at f/11-22 so this little amount probably won't have any significant effect on the final image, but if I were shooting wide open it probably would.

So my question is simple. Having not taken the time to do lots of testing, I am looking for advice. Trust my eye, or trust the camera? Of course I realize that the focus confirm is not entirely pinpoint accurate either and that there is a range within which it lights up, but today it seemed like it wasn't until I moved the focus just far enough for the light to go off that the subject looked its sharpest.

Any advice appreciated.

05-27-2014, 09:15 AM   #2
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May I add a tied-in question to this thread? How accurate can CATCH-IN-FOCUS be [on a K3] if you work deliberately and with a consistent method? As well as, or better than my 60+ years old eyes might be able to focus through the viewfinder? I'm thinking something like coming in towards the focus point slowly from the near distance side, in order to take maximum advantage of the circle of confusion tolerance. Thanks for any C-i-F advice from experience.
05-27-2014, 10:23 AM   #3
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You should examine the negative with a loupe to find the answer about what method yields the sharpest result. If the focusing screen is misaligned, for example, the image could look sharp in the viewfinder, but come out soft on the film.
05-27-2014, 10:24 AM   #4
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I trust my eyes and autofocus (or focus confirm with manual focus), but only because I try to pay attention to make sure both are trustworthy. I sometimes rely more on the one than the other; it depends what kind of shooting I'm doing at the time. I do like to actually see the focus whenever possible, even when I'm mainly relying on the camera. But with my progressive lens glasses, the ambient light, to speed or motion of the subject, and various other factors (including how tired I am), sometimes my eye isn't the best tool for the job. That's when I rely on the camera.

Focusing by eye begs the immediate question of how the viewfinder diopter is set, if focus-by-eye isn't agreeing with the focus confirm.

And of course AF (or MF focus confirm) depends upon a different sensor in the camera which might be out of calibration. This has created the whole craziness around "micro focus calibration" with modern DSLR's, their hyper-intolerant AF systems, and the sample variation between combinations of body & lens. I shoot the 645D so far, not the film 645's, though I did recently get a 645NII to try my hand at B&W film. But I don't believe focus calibration is a problem on the 645 system, unless an AF sensor has actually gone bad, the focusing screen is misaligned, or the camera or lens is damaged.

05-27-2014, 03:41 PM   #5
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Focus point confirmation in the majority of cameras that provide it is an arbitrary point based on distance rather than visual acuity; in essence, trust your eyes first, and agree with the camera unless it has focused somewhere other than your intention. If it looks out of focus, the chances are it will be out of focus because no camera or lens can mimic the acuity of human eyesight. You may also want to check your own eyes for any progressive loss that may require a dioptric correction for the camera. The final test of focus and edge acuity is under a 4 to 8x loupé on the lightbox.
05-27-2014, 04:46 PM   #6
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Thanks for all the feedback. I doubt it was a diopter setting issue since, if I understand it correctly, an out of focus diopter would render everything a bit blurry, and not cause OOF subjects to appear in focus. I will have the negatives in a few days but as mentioned, the lens was stopped down significantly so it probably won't be noticeable.
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