Autofocus issue with canon EF 28 mm f/1.8 on a 70D

Hi there!

I recently purchased a used canon lens EF 28 mm f/1.8 to go with my canon 70D. I made some tests and I find that when shooting in autofocus mode, with autofocus on one AF-point only (at or near the center), the zone of focus in the final picture is actually not exactly on the AF-point but slightly behind.

I made this test for several aperture value, from f/1.8 to f/6.3, and it does not change the problem significantly. All shots were taken without recomposing the picture.

The lens is in good state, no indication that it could have suffered any damage. However, can a certain damage on the lens trigger such an issue on the focus system?

Has anyone observed similar thing? Is there something I am missing?

Thank you in advance for any tips or feedback!

Best regards

PL

The 70D has MFA, try it

Dave

Hi Dave,

Thanks for the tip, didn't know about this nice feature! Will try it and keep you posted!

Regards

PL

Hi again Dave,

I tried the MFA and it seems to have improved the results a bit.

However, I think I am just simply and slightly disappointed by this lens... Hard to get sharp focus, and incredible high chromatic aberration between f/1.8 and f/2.5, even with the automatic correction function turned on. Or it is simply just too hard to switch from an IS lens to an older one...

Thanks for your help anyway!

Cheers,

PL

Sorry its not working for you, I did not think much of the 28 1.8 for the same reasons you give.

Best of luck.

Dave

I would check on the forums for this, because I think it is an issue with some 70Ds not being able to focus correctly with fast lenses (faster than f/2.8). I don't know if this has been resolved by now, but there were posts on it when the 70D first came out.

EDIT: I'm probably wrong. If your lens doesn't focus correctly by f/2.8 or higher, then the problem is not the 70D. I just remembered that you said it isn't good at f/6 either.

Sorry its not working for you, I did not think much of the 28 1.8 for the same reasons you give.

Best of luck.

Dave

I'd buy an EF 28mm f/1.8 IS USM in a flash!

Hi all,

Thanks for your messages. Actually, I've been making some more tests and the lens performs rather well (let's how I expect it to behave...) in Live View focus, with very sharp images in focus. The soft focus only occurs when using AF-points.

Anyway, I also find that I don't need to shoot so much wide open, all my shots are done at f/2.8 which gives the best results for my topics (mainly my daughter). Shooting higher than f/2.8 always brings the risk of having only her nose sharp...   And limiting the aperture to this value also has a great advantage: no more problematic chromatic aberration.

I also read about these supposed misfocus problem with the 70D but I think it performs great with all my other lenses. I am only an amateur, so there might be some things I still need to lear to be alble to overcome this AF-point issue on the 28mm f/1.8 lens.

Cheers!

PL