Nikon D7100 left focus issue

Started Apr 19, 2013 | Discussions thread
fireplace33
Senior MemberPosts: 1,501Gear list
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Re: good info
In reply to Mako2011, Apr 21, 2013

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

This summary was made from thes following detailed lists of image with my judgement on the focus result

D7100 image list part 1

D7100 image list part 2

D90 Image list

An example with EXIF of a good focus when using the middle focus point for the 17-50

Set up showing 3 targets about 3meters from camera D7100 + Sigma 17-50OS middle focus point

An example with EXIF of a bad focus when using the left focus point for the 17-50

same as before using left focus point

and 100% crop of these two shots of the middle target

Middle target of above image with central focus point used

Middle target of above image with left focus point used

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?

 fireplace33's gear list:fireplace33's gear list
Canon PowerShot G15 Nikon D90 Nikon D7100 Nikon AF-S DX Nikkor 35mm f/1.8G Nikon AF-S DX Nikkor 18-200mm f/3.5-5.6G ED VR II +11 more
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