Focus with 70-200 Sport 2.8

Hi all

i have mentioned this before in this forum, but now i have some more information.

My initial issue was, that the auto focus with my SDQ-H and the new 70-200 Sport f/2.8 was very unreliable. Especially with the OS enabled.

Sigma looked at the 'evidence' and they wanted the lens for test - they reported back, that they didn't experience any issues. They returned my lens, and ALSO send me a brand new lens to test, to see if there was any difference. (Nice guys!)

Then i mounted the new lens on the SDQ (not the SDQ-H) to see if the new lens was better ...... and it was. 10 shots 200mm handheld with OS on = 10 perfect hit. That was great. But then it struck me - i actually never used the 'first' 70-200 on the SDQ ONLY on the SDQ-H.

I then mounted the new lens on the SDQ-H and the focus issue was back! I made a series of tests - 2 shots 200mm f/7.1 - 2 shots 200mm f/4 - 2 shots 200mm f/2.8, handheld with OS on. On all 3 cameras SDQ, SDQ-H and the SD15. Here is 2 pictures, one from the SDQ-H and one from the SDQ (SD15 gave same result as SDQ):

These are screen shots showing 1:1. It is clearly visible, that the object position within the DOF is very different. On SDQ-H the object is very close to the front 'edge' of the DOF, where on the SDQ (and SD15) the object is about 60-70% into the DOF. I made the test (all 18 pictures) several times, and the result was the same.

It turned also up, that Sigma tested with a SDQ!

This makes actually sense, that i have inconsistent focus with the SDQ-H, since moving the camera as little as 1 mm will place the object out of focus.

The information is of course send to Sigma, and i hope they will respond at some point.

Here is a link to all 18 pictures: https://photos.app.goo.gl/YzvW22v3aLDWMvGDA

Does any of you clever guys have an explanation about this? Can i somehow cause it

It's  possible. My SDQ-H is to slow and less precise of the SDQ with same lens.

Specially with DG lens. Art 24-70, 105, 35 and 50mm.

Everyl single Sigma Body is a separate story.

No, my friend have a SDQ-H and is better than my SDQ-H.

Thank you for the answers - i understand that DSLR's can vary since they have components that are 'analog' and adjustable.  But as i understand cameras like the SDQ's they are purely digital with no adjustable components - so can someone please explain how the focus can vary from camera to camera?

Henrik,

Dare I say it, but I think your test target is not really the very best way of testing the AF.

Could you try it with a good Test Chart, maybe something like this one with the cameras mounted on a tripod.

S

Hi, reviving this old thread because I recently bought an SDQ H to substitute my SDQ and it's driving me crazy for the exact same reason: AF inconsistency, almost always the AF is at least slightly off, which on a Foveon sensor of course gets very apparent when you magnify the image (sometimes it's also completely off, I wonder why, since CDAF should be at play every time).

On my plain SDQ it was spot on almost always, now it's basically unusable for me, with lenses such the 105 F1.4 which have a razor thin DOF, but I've also experienced AF inconsistency also with the 18-35 F1,8 wide open at infinity, so the issue looks real to me.

Was there any follow-up from Sigma? Anyone experiencing the same level of issues with their SDQ H? To me for now it's basically a MF camera, if I want to be sure to have tack shapr pics that this marvellous sensor and Art lenses deserve..

da7329 wrote:

Did you try the sdq-h in crop mode similar to the sdq? I have use the sdq-h with many sigma sport and arts with very good AF results. 150-600sport 500f4 sport most of the late model arts. My 70-200 sport is in EF mount so cannot try. But shooting the same lens on the sdq-h and Sony a9 and a6400 I don’t notice missed focus from the sdq-h for static subjects.

DA

You may not get a response, he hasn't posted in over a year ...