Focus Problems

Hi all. I am new to the forum and this is my first post. I have two Canon 650d and a 100d. I also have Sigma 18-35mm f1.8 lens. Now I first thought that the focus problem was with the sigma and did a calibration. The lens was slightly ff. But now I have noticed an issue I never did before since I never tried calibrting lenses before and I learned to accept slightly soft images from my Canon 85mm f1.8. After all the tests with the Sigma I noticed that the camera focuses extremely well in landscape with most of the af sensors but in portrait it mainly works okish with the centre point only. Both lenses having same problem on both bodies. I suspect it to be a body issue. Can anyone help? Thanks

Edit: The cameras seem to work ok with kit 18-55mm stm lens at f4. Also works ok with Canon 50mm f1.8 at f2.8. The Sigma and 85mm were both used at f1.8.

There's lots on here about sigma art lenses having focus issues.

FooHead wrote:

There's lots on here about sigma art lenses having focus issues.

I did calibrate the Sigma and it now focuses well consistently in landscape. I mainly use centre af point or the one above it and both extremely sharp. Turn camera portrait and the extreme right sensor which is now placed on top give bad front focus. Same sensor in landscape works well. Similar problem with 85mm f1.8 but the 85 is more unpredictable.

If all your lenses are off it probably means your cameras are off. I know my 80D was pretty off and even a 10-18mm needed MFA and the depth of field on it is already pretty big. The Canon 85mm /1.8 was extremely reliable for me and with static subjects my hit rate is usually in the high 90's percentage-wise.

The focus issues is probably not as obvious in landscape due to the big depth of field. Shallow depth of field will make the issues more obvious.

I have a 50mm 1.4 that works terribly with my 80D using one-shot AF but it works great using AI Servo. Maybe try AI Servo. It works fine even with still subjects and it's worth a shot.

rmexpress22 wrote:

If all your lenses are off it probably means your cameras are off. I know my 80D was pretty off and even a 10-18mm needed MFA and the depth of field on it is already pretty big. The Canon 85mm /1.8 was extremely reliable for me and with static subjects my hit rate is usually in the high 90's percentage-wise.

The focus issues is probably not as obvious in landscape due to the big depth of field. Shallow depth of field will make the issues more obvious.

I have a 50mm 1.4 that works terribly with my 80D using one-shot AF but it works great using AI Servo. Maybe try AI Servo. It works fine even with still subjects and it's worth a shot.

Sorry when I say landscape I mean the camera is horizontal. And portrait I mean holding it vertical. Almost all my shots with my f1.8 lenses are shot at 1.8 or 2.8. The 50mm f1.8 focuses well at f2.8 in any orientation. The Sigma 18-35 focuses well at f1.8 when camera is horizontal but the same af point gives soft photos when camera is held vertical. Similar with the 85mm. I never took notice of the problem with 85mm till I tested the sigma and realised the 85mm had similar problem.