50D AutoFocus Micro Adjustment: amenity or necessity?

[BuddyO]

I had an XTi for a couple of years and recently upgraded to a new 50D. The XTi took good pics with my 24-105 L lens, but the camera was a bit small for my hands and I couldn't resist the upgrade bug. I love the feel and responsiveness of the camera, but I noticed that some of my family pics were a little soft. One in particular was taken inside in Av mode at F4, ISO 400, all autofocus points enabled, usingthe built in flash. I took a pic of 3 family members who were standing together and noticed that the one in the middle was out of focus. At first, I just blamed a thin DOFdue tothe F4 aperature setting and a mid focal length, but I'm starting to think the autofocus is out of wack.


I took identical pics, alternating between autofocus and manual focus (using liveview and 5x magnification - nice feature) and performed a Micro Adjustment on the autofocus until I got similar results tothe manual focus. I ended up with a +5 adjustment, indicating that the camera was front focusing by default.


Is this normal or does it mean the camera is not behaving as it should? Micro focus adjustment seems like a nice amenity, but has now turned necessity for me. Has anyone else experienced this?

[Sean Setters]

I'd say amenity. I have a 70-200mm f/2.8 L IS that I always thought missed focus (although not too terribly) on my XTi. Once on the 50D, though, I could dial in the focus using a microfocus adjustment. Other than the 70-200, all the rest of my lenses seem to work just fine with no microfocus adjustment.

[HiFiGuy1]

Out of curiosity, if you can determine that a lens is front- or back-focusing, is that something that Canon Service can and will take care of?


Since you say AF MicroAdjust is an amenity, and you only have one lens that isn't focusing accurately out of the box, I just wondered. Also, is this the norm? It seems like there are lots of people with multiple lenses that are slightly out in one direction or another. If it weren't a common problem, why would Canon develop a solution for it?


All serious questions that I honestly don't know the answer to, not rhetorical.

[Sean Setters]

Out of curiosity, if you can determine that a lens is front- or back-focusing, is that something that Canon Service can and will take care of?

When I first got the 70-200, I sent it to Canon's Service Repair because I thought there was a focus issue. They sent it back to me saying there wasn't anything wrong with it. They said if I noticed any further issues, I'd have to send my camera in with the lens. I lived with it. Then I got the 50D, and was able to fix the issue with a microadjustment.


The reason I said amenity is this--most of the time, it isn't needed (when all works as it should). When it doesn't, Canon should be able to fix focus with a warranty repair. However, having microfocus adjustment allows you to work with lenses that have relatively small focusing issues without the need for sending it (and your camera) in for calibration.

[Daniel Browning]

Is this normal or does it mean the camera is not behaving as it should?

It's not normal in the sense that the system is not performing optimally. But it is normal in the sense that many people have the same problem.

Micro focus adjustment seems like a nice amenity, but has now turned necessity for me. Has anyone else experienced this?

Yes, I consider it vital for autofocus. I would pay hundreds extra just for that one feature if I had to. It would be nice if it supported more advanced settings (zoom ranges, focus ranges, etc.).

[Joel]

The LensRentals blog had a great writeup on this some time back.


The need of this feature differs per lens or camera/lens combination. I haven't been able to play with it myself, because I've no Autofocus Micro Adjustment enabled body (yet [;-)]).


What about Autofocus Micro Adjustment on primes vs zooms? Since - as far as I understand - the adjustment varies per focal length.

[HiFiGuy1]

That Lens Rentals article is very insightful. His take on it is what I thought my take would be, but not ever having owned a body with AF Microadjust, I didn't know for sure.


I know one thing, though. My backup body is going to be at least a 50D going forward. If I get a really nice one, it will probably even supplant my 40D as my primary, with the 40D as the backup.

[BuddyO]

Thanks to all who have responded, I now feel much better about my 50D. Joel, that LensRentals article was most informative and interesting, thank you.


My initial reaction from some of my early pics had made me second guess the purchase. I had assummed that Canon had to add microfocus adjustment to this particular model because they recognized early on that it's autofocusmay be problematic. I had not experiencedthis problem with my XTi nor my 40D. I had not mentioned this earlier, but I had purchased a refurbished 40D just days prior andwas very happy with the results it gave me with my 24-105L. A very nice upgrade from the Rebel. Unfortunately, it died after two days and I was never able to power it back up (yes, I recharged the battery back to full capacity [] and I cleaned the battery and camera contacts), so off it went back to the retailer. With no other refurbed 40Ds in stock, I opted for a new 50D at a good price, asI did not want to wait for another 40D to become available.


Now that I have adjusted the camera for my particularlens, pics are nice and sharp. I now believe that Microfocus adjustment is an amenity, but I also see it asa must have, now that I understand how manufacturing tolerances come into play and how they can adversly affect individual camera/lens combos, allowing othercombos to mateperfectly.