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S230
4th of January 2005 (Tue), 08:24
I finally tested my new Canon 50mm 1.8 lens on my Digital Rebel and I noticed that I either get very sharp photos or really out of focus. This was mainly a problem with AutoFocus mode.
Had anyone come across this problem and what is the best method of resolving this? I still have warranty but before I send it in, I want to do the following...

What is the best method of testing the focusing?
What can I do to try and fix this?

Thanks.
mr.photoguy
4th of January 2005 (Tue), 08:34
I have learned that with the 50 1.8..
If you are shooting at 1.8 the DOF is going to be so shallow that you have to know where you are putting the focusing point.
You have to know where you want to be in focus, and then realize that a certain space outside of that area will and can be out of focus because the DOF is so shallow.

What F stop are you shooting at .
S230
4th of January 2005 (Tue), 09:30
I have learned that with the 50 1.8..
If you are shooting at 1.8 the DOF is going to be so shallow that you have to know where you are putting the focusing point.
You have to know where you want to be in focus, and then realize that a certain space outside of that area will and can be out of focus because the DOF is so shallow.

What F stop are you shooting at .

Thanks for the quick response. The F stop is at 1.8. I also noticed that even when I put on a tripod, it's focusing somewhere else other than centre AF point. The spot I noticed is 5mm towards the lower right side of the point and unfortunately it's not consistent. When I switch to manual mode, it's more consistent.
cmM
4th of January 2005 (Tue), 09:46
I wonder what it would be like shooting a 50mm 1.0 wide open :p
mr.photoguy
4th of January 2005 (Tue), 09:50
I don't think it would be much fun shooting a 50mm at f1.0 ..

To be honest I usually stop down to f2.0 or a bit higher. That helps me keep what I want in focus.

Try that and see what you get .
S230
4th of January 2005 (Tue), 11:10
I was actually given a link to do testing and is really intersting to see how it works out.
http://www.photo.net/learn/focustest/
Pekka
4th of January 2005 (Tue), 11:17
See http://photography-on-the.net/forum/showthread.php?t=10526 for more accurate testing scheme.