Just wanted to share my findings today to see if others experience the same issue.
At first, I thought it was limited to my 35L, but does the same exact thing with my 24-105L. The shallow DOF of the 35L just shows it much more.
I calibrated my 35L to my body using Focal... Extremely reliable AF performance using center point. Never misses. Switch to any of the outer cross AF points and lens front focuses quite a bit. You can see the DOF scale shift over... Checked on multiple targets at various distances on a tripod (so distance does not change) and consistently the DOF scale shifts to the left once I switch to outer AF points. Resulting in soft shots wide open using outer AF points at large apertures.
I thought it was just limited to that lens, but then I tried it with my 24-105... Under 50mm, it shows the exact same behavior. Over 50mm, it does not appear to do the shift.
Almost like with wider lenses, the outer AF points are having trouble locking on. I plan to try my 135L next to see if that does it as well... If my theory is correct, it will not shift due to the FL. And from my shooting with it so far, have not seen this happen either.
Just wanted to share this with everyone though. I plan to send to Canon if firmware does not address this issue with the AF.
p.1 #2 · 5D3 outside AF point issue with wide lenses
Is it possible that what you are seeing is field curvature of the lens? Seems to me that if the lens has field curvature and you start off with center-point focus and then shift to edge-point focus you could see a focus change and it would be legitimate for the new focus point.
p.1 #3 · 5D3 outside AF point issue with wide lenses
I thought that, but I never really had this issue with the 5D2? I was able to use the outer points with great results in good light. It significantly front focuses now with the 5D3.
It basically makes using the 35L with outer points a no go if you want sharp focus. Focus and recomposing yields better results.
p.1 #5 · 5D3 outside AF point issue with wide lenses
Just to clarify, when you say it front focuses are you saying it front focuses at the outer focus point? In other words, the image AT THAT POINT is not sharp?
I assume you are focusing on something flat like the FoCal target sheet?
p.1 #6 · 5D3 outside AF point issue with wide lenses
gpchase,
For those who bought the "pro" version of the software he released a beta that supports the 5D3... The only drawback is the software can't change the MA value, so it prompts you to do it as you go along. Works great otherwise. Until Canon releases the SDK for it, then he can implement the automatic MA changes.
Eyeball,
Yes, it front focuses with outer AF points. For example:
Center AF:
Outside cross AF point:
Those using the 35L wide open. Subject well over 20' away, so DOF should be fine. As you can see, much softer using the outer AF points. If I focus and recompose the image is much sharper then using the AF point directly. The focus point moves considerably if it can throw a subject 20' away out of sharp focus...
Setting up the camera on a tripod square with a well-lit wall, I placed two Focal targets (one at center AF point, one at outside AF point) and allowing the camera to lock focus multiple times at each, you can see on the DOF scale with both the 35L and 24-105L that it shifts considerably to the left. You just see a much bigger impact on 35L IQ due to the aperture. The 24-105 hides it more. I did the same test with the 135L and the focus was the same with either center or edge AF point. Seems to happen with wide angle only.
And not only with targets on a wall, but the same results with anything I try to use outer AF points with. At farther distances the difference in the DOF scale increases between center and outside AF point. For example, my shed (above). But even taking pictures of the dog, cars parked out front, etc... Outside points are much softer.
p.1 #11 · 5D3 outside AF point issue with wide lenses
Invertalon,
Thanks for sharing your test results. I remember a long time ago somebody here was having a similar issue with the 35L and a 1DsII (I think). Of course in absolutely useless fashion I can't remember if the person got it fixed and what the outcome was if so. Hope you get this resolved. Pretty well defeats the purpose to have awesome outer AF points if they front focus all the time.
p.1 #12 · 5D3 outside AF point issue with wide lenses
Over on POTN I have a similar post and others are reporting the same behavior.
Basically, it seems any wide angle lens (let's say under 50mm) will shift when you use the outer AF points versus the center point.
You may not notice any IQ difference with some lenses like the 24-105L due to the huge DOF, but will with faster, large aperture lenses. I did not see any IQ difference with my 24-105, but you clearly see the focus scale shift. Two others on POTN have had the same behavior now.
So I wonder if this is a wide-spread issue or just isolated. Either way, hope it can be fixed. The AF performance is stellar all around, except for wide lenses using outer AF points... Which sucks, since I love using my 35L with outer AF points. I guess I will just focus/recompose until fixed. I plan to wait for the firmware and if that does not address it, send the body in to Canon to have them play around with it.
p.1 #14 · 5D3 outside AF point issue with wide lenses
Thanks!
Your lens does not need to be perfectly MA'd or anything... Since the shift will be relative to whatever the camera is doing anyway. Just watch the focus scale with both, not relying on IQ especially with the 24-105 due to reasons above, but the 35L you should see some difference IQ wise unless it is backfocusing with the center point. But you will see the shift in focus scale regardless.
p.1 #16 · 5D3 outside AF point issue with wide lenses
Well this is quick and dirty..it's late here so nothing outdoors but this from my comfy den chair..
focus is far top right point on golfing plaque with center on the base of the 1DMKlV @ 1.4
With zoom the text on the MKlV appears sharp...does this contribute any data positive or other ?
p.1 #19 · 5D3 outside AF point issue with wide lenses
gpchase,
You can easily run the test indoors or outdoors. Hard to say if your example is good/bad, but you can find out if it is doing this without taking any pictures at all.
How I would recommend testing:
1.) Place camera on tripod. Aim at high contrast target with little room for focus errors.
2.) AF using center point. Watch focus scale on the lens. De-focus and let aquire focus a few times, watch to see where the lens ends up on the focus scale after a few times. For example, let's say it lands at the 3ft mark on the scale.
3.) Shift tripod head without shifting distance from target. Align target with outer AF point. Once situated, defocus and let the camera acquire focus. Do this a few times and check out the results. Remember, greater distances seem to show the problem more then closer subjects, although I saw it with both.
4.) In my experience, the center point showed that 3ft mark with center, and would shift left over to about 2.5ft (just an example) with outer AF point. Showing the body is front focusing. Now remember, if testing with a 24-105 or 24-70, etc... Due to the smaller apertures, you won't see the results as clearly as you will faster prime lenses. Which is why the 35L shows it so well.
Hope this helps. Appreciate everybody who is testing the combo... Hoping this will help myself as well as others who have the issue. Seem to have quite a few who are so far, so it is not a single-user issue.
p.1 #20 · 5D3 outside AF point issue with wide lenses
I just shot my brick fireplace from 10' with all four corner focus points of the lens and the center point. Each point focused on bricks and every file appeared okay although the center seemed sharper overall..??
