The Sigma 35 1.4 lens is a phenomenal lens. It is sharp wide open and just handle beautifully, in fact on my D3S it is very sharp using every focus point. UNTIL... I attached my SB-800 and then all of a sudden I have OOF issues, back focus and front focus issues. Which focus issue I have varies on the distance of the subject and even then it is inconsistent. Sometimes it may front focus, then OOF then back focus.
I have tested handheld, and on a tri-pod. When hand held the shutter speed is @ 100. The issue is worst from f/1.4-f/4 then it gets better but the image is soft compared to not using my SB-800.
Is the problem the SB-800, or is it that you're working in lower light? Ie what happens if you go outside in full daylight and use the SB-800 as fill flash? I would guess that if you do that, you'll get 100% spot on focus.
The fact that you're at 1/100th at (probably) f/1.4 strongly implies that you're in a low-light environment.
_____ Brian... a bicoastal Nikonian and Team Member
My gallery is online. Comments and critique welcomed any time!
I have tried that test as well and the problem persists. I contacted Sigma, it is a known issue and recommended I either send it in for repair or return it to the point of sale for an exchange.
I have done further online research and there are some users experiencing the same problem and one of the users was asked to send the camera in with the lens after the 2nd repair attempt and when it came back on the 3rd try it was spot on with and without the flashgun.
What I found out from Sigma is it is a known issue that the 35 1.4 with a Nikon flash using focus assist will cause the lens to be OOF, Backfocus, or Frontfocus. I was shocked and thought something went terribly wrong with the lens and would not have thought it was due to the focus assist on the SB-800.
I shoot with D3Ss and SB-800s and the issue is repeatable time after time but where the lens focus is not. Sometimes it will be OOF, or BF or FF, it is not consistent. I contacted Sigma and they said to send it in as it is a known issue (I read on another forum about similar issues and for one end user it came down to sending the body and lens in). I have only had the lens for a week so I am going to return it and wait for them to figure it out with the Nikon Flashes.
Here are my findings:
1. Using no flash - Spot on and tack sharp even at 1.4 2. Using in low light with ISO pumped up with no flash - Spot on and sharp even at 1.4 3. Using Nikon flash as fill light in bright daylight - Spot on and tack sharp even at 1.4 4. Using Nikon flash in low light with focus assist - Focus is all over the place and inconsistent and not once nailing a shot 5. Using Nikon flash in low light then turning off focus assist after using focus assist - Focus is all over the place and inconsistent and not once nailing a shot 6. Using Nikon flash with focus assist turned off before attaching to D3S - Focus consistent 80% of the time but images are softer than normal. CA seen for the first time but disappears by f/2.8
It wouldn't be big of an issue for me if I didn't shoot events in clubs and dark venues on a regular. I found this defect on assignment and was frustrated because of it and a lot of missed shots.
I hope this help some people out there. But I still believe the Sigma 35 1.4 is a tremendous lens with a minor flaw (that is being resolved by Sigma). Once it is fixed I will be adding it back to my arsenal of lenses. It really is that GREAT!
Update: I spoke to Sigma USA tech and was told that there is a firmware update being developed in Japan to fix the outer focus point issues and he said he is not sure but it may fix the focus issues with the Nikon Flashes. He didn't have an ETA, he just said they are working on it. So I guess we have to stay tuned.
I have been waiting to re-purchase the Sigma 35 f/1.4, does anyone know if the outer focus point out of focus issue and the use of the flashgun with out of focus issues have been resolved? I'm really missing this lens as my event lens and photojournalism lens. Any update will be greatly appreciated.