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I had previously mentioned in another thread that a recent copy of this lens severely front focused on all outer focus points on my D800. This is even after the latest firmware update. I wanted to share additional information regarding two new copies I had just received.
Last week I received a new copy from B&H. Despite the serial number being much higher than the first copy the lens did not come with the latest firmware. I decided to test it as is so I can confirm that the firmware affects the focusing despite Sigma's claim that it does not. With the old firmware the lens back focused significantly using the left side autofocus points. The center and right were fine. After updating to the latest firmware the left and center focus points worked great. However, the right focus point was still off by +7 using the D800's focus tuning. This lens also squeaks during autofocus.
I had also received another copy from Amazon. This lens had a much higher serial number than B&H and did come pre-loaded with the latest firmware. Ignoring the leading digits in the serial number the B&H copy was in the 131,000 range and the Amazon copy was 151,000. My first B&H copy was 68,000. All lenses were ordered within 1 week of each other. It seems that Amazon has fresher stock than B&H.
The Amazon copy is able to focus correctly on all focus points. However, it does require a D800 focus tuning of +5. I've checked the focus using both day light and artificial lighting and the focus seems to be good. I've also checked using distances at MFD and 50 feet and focus still worked well. I've tried using it outside with moving targets and it seems to nail focus.
My conclusion is that, despite the latest firmware helping significantly, there are still sample to sample variations out there which affect the autofocus. You may still need to be prepared to play some lens roulette to get a good copy.
UPDATE: I did some more testing and it seems that this lens does focus shift in different lighting as others have reported. When I originally tested the lens I used daylight and LED bulbs which were pretty close to 5000K. However, when I used the tungsten modeling lights on my strobes the lens will front focus 5 clicks on the D800 tuning scale. I realize that focus shift across lighting conditions is normal. However, I'm wondering if it's more severe with the Sigma 35mm. The focus shift is dramatic enough that I wouldn't be able to nail focus, at f/1.4, when I go from outdoors to indoors.
Edited on Sep 01, 2013 at 10:06 PM · View previous versions
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