This is my first post to this forum so if something is not right please understand.
I just purchased a 20D along with the 50mm f1.4, 85mm f1.8 and 17-40mm f4 L lenses and I think my camera is having focusing problems. I just read a related article on Canon focusing in this forum and after reading the article I am not sure if the test I devised and discussed with Canon was actually a good one or not. Can someone who knows more about focusing issues tell me if my test was good or not?
I took some music CD cases and laid them on a table so I could see the label on the backs. I put a double CD in the middle and used this as my single one shot AF point. I then placed 8 CD's on the left and right of this central double CD. The CD's on the left are coming towards the camera at quarter inch increments, and the CD's on the right were farther away from the center focusing CD in the same quarter inch increments. The last CD on either end was two inches closer (left side) or two inches farther (right side) away from the central focusing CD. When I placed the single central focusing point right in the middle of the double focusing CD, the image seemed to be focused best on the left CD's, and even those were not in focus. I started at the bottom end of the aperture settings (f1.4) and worked my way up, but always had the same problem. The images seemed most in focus on the leftmost CD's, even though I was focusing on the center double CD case. I am using a single focus point, Aperture priority, one shot AF, tripod with timed release, ASA 100 and the CD's are about six feet away from the camera. I then look at the images at 100% and notice the out of focus issues. I did this test with both the 50mm and 85mm lenses, and came out with the same issues. Canon suggested turning up the sharpening and trying some shots with manual focus. I did both of these and even with the manual focus, the CD's on the left were always closer to being in focus than the center CD's, which is what I was focusing on. Was my focusing test a good one? Does my camera have focusing problems, or am I doing something wrong or expecting too much from my camera? My camera should be arriving at Canon service in Irvine, CA today and I am wondering what they will say. Help ! ?
I did not have any filters on the lens. I just wanted a little confirmation that the test I was doing was reasonable and would indicate a focusing problem. From Marks reply it sounds like they will correct the problem. After reading the other focusing post I wasn't quite sure if my test was reasonable or not. Thank you for your replies.
If your center CD had an area of good contrast (not just very tiny print), and you were using decent light then your test sounds reasonable. It certainly suggests the camera is consistently front-focusing which Canon can fix easily. The 50/1.4, at least mine, has inconsistent AF which can be seen mostly in wide aperture shots, but this doesn't sound like the cause of your problems.
FYI -- your 20D always performs AF at the lens' widest aperture no matter what setting you actually use for the exposure. The widest aperture shots will just make any AF issues more obvious due to the resulting shallow DOF.
The center CD had good contrast, and I picked all of the CD's with white backgrounds and dark lettering for that reason. The black background with different color lettering didn't provide enough contrast, so I used the CD's with white backgrounds. Testing the DOF on the 50mm f1.4 was one of the reasons I was doing this test. I wanted to see how shallow the DOF was at the wide open apertures. But the test never got that far due to the lack of focus. Does anyone know how deep the DOF might be at f1.4? I see photos of faces where the eyes may be in focus but the nose or other feature is not. Is the DOF really just a couple of inches at f1.4?
