bizarre experience with 3 copies of Nikon D5100

Started Oct 15, 2011 | Discussions thread
ForumParentFirstPreviousNextNext unread
Flat view
sif20047
Junior MemberPosts: 27
Like?
bizarre experience with 3 copies of Nikon D5100
Oct 15, 2011

I have a very bizarre experience with 3 copies of Nikon D5100, hope to get some suggestions here.

I bought my first D5100 a couple of weeks ago. At that time I only dad some zooms. I tested some focus chart and found that it had backfocusing problem, so I returned it for another one.

The second was perfect with focus chart. Later on I acquired a couple of primes, 50 1.8g, 35 1.8g, sigma 50 1.4, sigma 85 1.4 and 105 VR, after a few days shooting in real world situations I feel like many images with these primes are soft. So I did another focusing test. I set up several rectangular boxes on a table, they were 5 inches apart away from me. The boxes have identical lettering on the outside, so it was easy to compare the sharpness between them. The front surface of the boxes were parallel to my camera sensor. I used tripod, remote control, ISO 400 so that the shutter speed never went below 1/200. I also setup the camera so that the distances between the camera and subject were similar to real world situations. With 35mm, it's 1.8m; 50mm, it is 2.5m; 85 and 105mm, it is 3.5m. All shots were taken wide open. I took 10 shots per lens, always waited a second after focus lock. I also borrowed my friend's 35 1.8g and sigma 85 1.4 for this test. You know what? All lens except 50 1.8g backfocus with this D5100. The degree of backfocus varies with lens, but I could easily tell by comparing the sharpness of the lettering on the boxes. If I moved 1 m closer in all situations, all lens were perfect. Liveview focus was also perfect.

Knowing that I would return this D5100 for sure, I bought another D5100 for side by side comparison. The results were almost the same except that the third D5100 worked better with sigma 50 1.4 (5 out of 10 shots were spot on). Finally, I took my old D50 from the closet and did the same testing, Now every lens are spot on. For sigma primes, I actually took 20 shots just to make sure. This is so strange. Did I do anything wrong? How come three D5100 all have backfocusing problems but the D50 is perfect. I googled and did not find many complaints about D5100. What are the odds?

ForumParentFirstPreviousNextNext unread
Flat view
Post (hide subjects)Posted by
ForumParentFirstPreviousNextNext unread
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark post MMy threads
Color scheme? Blue / Yellow