A700 f2,8-af sensor?

[js1]

Hi,

Lately I´ve been reading several topics on different forums about people who has experienced bad af-performance when using lenses faster than 2,8.
I myself have this problem and David also experienced it during the "A700 shoots Cirque de soleil".

I know a guy who had to send his A700 to Hungary (for weeks) to fix this issue.

Does anybody have more info about this. Is it a major problem coming up or just a number of bad af-sensors.


/Jörgen

[Dr. Harout]

Haven't tried on a lens with a greater opening than 2.8, but will gladly do if anyone could send me such a lens

OK, let's get serious. Sony has 2 such lenses yet (the 35/1.4 and 50/1.4) Carl Zeiss has 2 also (85/1.4 and 135/1.8 yet) and as for Konica-Minolta there are around 15 such lenses of which some are same lenses with minor changes. I haven't heard of such a case of having difficulty in focusing or bad AF with Sony or Zeiss lenses, but AFAIK the complaints were rather for Minolta lenses (might be wrong, and will be glad to have info on this issue).

This question is very important, and I think someone here might be interested in elucidating it. At least I hope so.

[stroberaver]

David also experienced it during the "A700 shoots Cirque de soleil".

I was under the impression that this was a tendancy of the 50mm lens, not the fact that it was faster than f/2.8. I may be wrong, but that's how I interpreted DK's report. I've been doing my own brief test with my 50/1.7 and my new A700 but have only been able to use it indoors in my flat so far, and haven't been able to recreate the conditions. I've been taking plenty pictures with my different lenses to test for backfocussing, and although I've not yet done anything sufficiently systematic or conclusive, I'm not yet 100% sure that my A700 doesn't occasionally backfocus.

[js1]

I´ve heard about a guy having problems with both his minolta 50/1,7 and Tamron 17-50/2,8. After repair in Hungary the camera became fine.

I´ve also read (on Dyxum) about at least 2 guys having bf with the Sony 70-200/2,8.

If I focus at about 5m with my 50/1,7 the actual focuspoint is at about 7m. But when I checked with a Sony 50/2,8Macro on my camera it was spot
on.

I´ve borrowed a Minolta 17-35/2,8-4 from a friend of mine and in the wide end the af isn´t 100%. I have to zoom in, lock focus, and back out to 17mm
to achieve proper af. I must say I´m confused.
My favorite lens Minolta 24-105/3,5-4 has given me 99,9% sharp pictures (thank god) and my beercan also feels very confident.
One of the major reasons to switch from Dynax5D to Sony A700 was the af-performance, which everyone
praised in the beginning, I´m not 100% convinced at the moment.

[Dr. Harout]

Allow me to add this too:
While focusing on a subject with SAL16105 the focusing differed on 16mm and 105mm positions (the subject was sharp at the long end while soft at the wide one). The AF was precise while on 105, but not on 16 (may I say that 16-105 is something in between a zoom and variofocal?) However, that's not a major concern for me.
But something that might interest us all is focusing with Sony 50/2.8 Macro on a close subject (less than a meter) with AF (yes AF). Comparing to A100, the same lens did not hunt much, even in non-bright circumstances. Even, the hunting was quite rare. Would be happy if someone could test the Sony and Minolta simultaneously to see for such differences.
Overall, we have yet much to learn and such a forum can be of great assistance.