Photoclubalpha

Hi,

In the article "A700 shoots Cirque de soleil" You (David) experienced sever backfocus with the
Minolta 50/1,4. You said you where about investigate further.

I have experienced similar problems with my Minolta 50/1,7 and a Minolta 50/1,4 which I
borrowed from a friend on my A700.
I tried the two lenses on another A700 in a camerastore with similar results. Heavy b/f when
the shootingdistances is about 7-12m (roughly). My other lenses works fine, both new Sonys and
older Minoltas.

Have You found any reason for the b/f or are you still investigating.

Please advise.

Regards

/Jörgen

It used to happen on the 7D, on the 5D, on the A100 - it just seems to be a fact of life with these lenses at distances around 10m. It looks as if the A200 and A350 have exactly the same issue.

David

Hi David,
Can you explain what you mean by severe back focus and what problems it causes?

It means that the camera will appear to focus perfectly on a subject, but the actual focus point when you view the picture turns out to be behind the subject. Front focus means it is in front. All DSLRs have this problem, to some extent, and it depends on the lens and the body alike. The precision needed for perfect focusing with a 50mm f1.4 is great; DSLRs are only made to a certain standard (they are mass produced) and corrections are made on a machine which measures the error and loads a table into the CPU to correct the focus. Sometimes this table does not agree with a particular lens, it has to be general. Other times, there is an error in the camera caused perhaps by something settling during transport from the factory to the final owner.

David