Nikon D7100 left focus issue

Started Apr 19, 2013 | Discussions thread
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Mako2011 MOD
Forum ProPosts: 19,195
possible solution
In reply to fireplace33, Apr 21, 2013

fireplace33 wrote:

I finally found some time,  after stacking up several cubic meters of firewood this weekend, to make some more detailed tests, and found some confusing results?

I’m no longer 100% sure if I really have (just) the classical “left focus issue” after all?  but I certainly do have some sort of focussing problem or some combination of camera or lens problems ?

I would be grateful if anyone can help me make sense of all these results and help me determine the exact problem(s) so I know what to send back.

I made over 130 images and afterwards analysed each one in terms of “good”, “medium” , “bad” or “very bad” focus quality. I did this evaluation like in a “blind test” without looking at any of the settings as I judged the images.

Tried 5 different lenses  on both the D90 & D7100 and summarised all the results in excel.

Also made each image with both live view and while focussing through the viewfinder to test both PDAF and CDAF.

The images were made outside in bright uniform light on a tripod with shutter speeds of about 1/3000 or faster. So I could turn off image stabilisation and did not need to use Mirror lock up or remote triggers.

Used AF-S and set up 3 flat focus targets. I shot each case 2 times to test for consistency.

Priority was set to “focus”, also made sure the AF fine tuning was done  (with dot tuning method) for each lens.

I positioned the camera at a distance of about 3m so that the left, centre and right focus points were aimed directly at the 3 targets, took the photo and noted the image number each time. Really quite time consuming!

The D7100 result summary

D7100 result summary

The D90 result summary

D90 Results summary

A few more examples are in my gallery. If you need any other particular examples from the table I can post them too if it helps. I had to resize the shots to maximum 3000 pixels on one side to load into DP review.

I think you can see why I was disappointed , but now with these results and your help maybe we can get to the bottom of this?

Wow, you have been thorough. If I read this right...looks like 3 of the lenses may have issues, especially if the results are all that "bad" as in your example. Makes me think three of the lenses are off or decentered slightly.

You might try this and get usable results. On the D7100, fine tune the Sigma's and the 50mm using the center focus point...then retest left and right side focus points wide open with the new fine tune settings. You might find DOF has shifted enough to give good results across the range. D90 won't let you fine tune so lens recalibration may be needed for that body...resulting in new fine tune setting for the D7100 with the recalibrated lenses.

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