EF 85 mm f/1.8 with 70D: front focusing?

Hi all!

I have recently purchased the 85 mm f/1.8 and I made some first shots that were really nice, especially head shots. But today I tried some shots at longer reach (about 5 m) and I am surprised to see that the lens seems to front focus rather significantly.

On the image below, AF-point is located on the face (nose/mouth) whereas the focus plane is somewhere in the grass ahead of the character.

It cannot be that she moved or anything like that (I took several photos that all have the same problem).

When I shot at closer reach (head shots), I don't see the same effect, at least not at strong, which make the result acceptable.

I have been testing some MFA and although I did not have the time to make lots of test shots, it seems to solve the problem ... at longer reach only because with the correction, my focus is then completely messed up for head shots :-s

Doing my tests, I even noticed that at closer reach, the lens/camera can sometimes front or back focus. But this is maybe something I am doing wrong there.

My main issue is that I don't think it is normal to have this clear front focusing at longer reach. This makes the lens pretty tricky to use since I need to adjust the MFA all the time. Have other users observed similar behaviour?

I ask this now because I have a week or so to return the lens if I am convinced that it is the best solution.

Thanks for your help and feedback!

Cheers

PL

Appears like a front focus issue unless u are constantly focussing incorrectly.
1. Can u try single point AF and use the centre point to focus?
2. Before MFA, try to shoot using a tripod on a static object which is located in the same distance.
3. If the problems persist, then perform MFA or exchange the lens.

My first copy of my 85/1.8 went back for focusing issues. Second is pretty solid. Get a stationary subject with good contrast in good light. Tape a magazine cover to your house outside or something but makes sure it's flat. Set camera up on a tripod and take a few shots in live view and then switch to through the viewfinder shooting. This will test the phase detection AF mode against the contrast detect mode. If the live view shots are much sharper than viewfinder, exchange the lens.

Hi all and thanks for your messages. I am currently on holiday and it s hard to find good conditions to make proper tests.
However, today's shots, using MFA, gave better results, for both closer and longer reach. To be continued...
Will keep you posted.
Cheers!
PL

Hi!

I found some time to make some more tests with fixed camera.

I was purposely at f/1.8 and tried to achieve focus when shooting at a magazine cover located ca 3-4 m from the camera.

AF-single point on the center AF-point.

As you can see on the pictures below, it looks like I need a MFA of +12 AF to get a good focus (almost as good as what I can get with Live View). But the difference with same test but without MFA is not super big, I find.

MFA: +12 AF

No MFA

Another thing: I did have rather volatile results, even with fixed camera. I do all I know to shoot without disturbing the focus (not moving if possible, single shot AF on center point, no recomposition), but are there other methods that could help improving my focus technique??

Finally, I think I can be rather satisfied in how my lens perform (and only wish to improve my technique). Do you guys also agree or do you see a clear indication that I got a bad copy?

Thanks in advance for your help!

Cheers

PL

My experience with an old copy of the same lens was that it required +18 MFA and produced fantastic results at f/4, very good results at f/2.8 and acceptable results most of the time at f/1.8. I didn't buy a copy of the lens although at f/4 the results were amazing simply because I put more money into a 70-200 f/4 IS - and had a 50mm f/1.4 which is a lot more erratic.

The 85mm would have been a keeper though but not if I didn't have MFA.

cb