oly720man From United Kingdom, joined May 2004, 7113 posts, RR: 10
Reply 3, posted (2 years 7 months 5 days 9 hours ago) and read 3736 times:
If half the image is in focus and half isn't it may be that something has worn and got out of alignment, but you'd probably expect a gradual variation from one side of the image to the other, not a distinct variation
Clickhappy From United States of America, joined Sep 2001, 9823 posts, RR: 64
Reply 4, posted (2 years 7 months 5 days 9 hours ago) and read 3730 times:
Easiest way to test if you have a front focus or back focus issue is take three cans and stagger them, use a center point AF sensor with a stopped down aperture, f/8 or 11, and focus on the center can.
ckw From UK - England, joined Aug 2010, 813 posts, RR: 14
Reply 5, posted (2 years 7 months 4 days 21 hours ago) and read 3632 times:
Could be lens alignment or a problem with the is system.
Pin a newspaper on a wall, put the camera on a tripod at exactly 90 degrees to it and take some test shots at various aperture with is on and off. If the pics come out sharp across the frame, the lens alignment & IS are OK.
Front & back focus can be checked as per Royal's suggestion.
But, is this just one shot? Consistenty repeatable? It could also be as simple as a mis-selected AF point! I know that sounds obvious, but I've done it myself (more than once!).
CaptainKramer From United Kingdom, joined Feb 2012, 239 posts, RR: 0
Reply 7, posted (2 years 7 months 4 days 5 hours ago) and read 3542 times:
I have had partial soft focus issues as you have described, with all my Canon lens I use from time to time, they include the Canon 100-400mm, Canon 70-200mm f4, although I have never had a problem with my Canon 200mm 2.8 prime lens.
If it does start to happen I switch the battery off, take the lens off and the then twist it back on as you normally do, lining up the red dots, it seems to reset things internally for some reason, and I don't normally have a problem after that.
Other times I have had an issue with soft focus, after it initially working fine, is when I am taking a shot of an aircraft on the long end of the lens and a tall truck or bus crosses in the foreground as I fire off a few shots, this can mess up the auto tracking focus system, same solution again, switch camera off take lens off, then twist it back on, problem solved.