David Kwok
Senior Member
here is a personal example.
http://farm4.static.flickr.com/3012/3093802516_142447492e_o.jpg
I targetted its eyes and then re-composed to add more leaves in the composition but forgot to adjust aperture or rather i forgot i left it at F/5.6 on extreme zoom. by right shouldnt be a problem, by left the subject was slightly blurred but the leaves were okay.
Let me see. You are actually quite far away from the subject right ? You zoom in to a focal length of 250mm ? I read into the EXIF unless I'm mistaken. At f/5.6, the DOF is quite shallow. SO basically your recompose shifted the angle of the focal plane and hence the eyes becomes infront of the focal plane because you recompose from left to right. In this situation, I recommend you shift your focus point instead of recompose. That's normally why some people complain about backfocus or front focus for prime lens of f/1.4 because they didn't realise that while they recompose, the focal plane changed in angle and it's a different situation altogether. That's not to say those claims about back and front focus ain't true, just that it's hard to differentiate between a technical issue and a technique issue at times.