Focusing problems with 300D...

[JusSmith]

Just got myself the 50mm f/1.8 II and after playing found an awful lot of the shots were out of focus. I then looked back at some other shots with other lenses and I'm not quite convinced with these, but then again the apertures are alot smaller.

So I read the threads and did the tests and here are the results.

First the 50mm at f/1.8, 1/80s, ISO 100 (2 feet from subject, focused on 'recomm')
www.pbase.com/jussmith/image/41423508 (http://www.pbase.com/jussmith/image/41423508)

Then the 50mm at f/4, 1/15s, ISO 100
www.pbase.com/jussmith/image/41423509 (http://www.pbase.com/jussmith/image/41423509)

Then a 28-105 at 50mm, f/4, 1/15s, ISO 100 (isn't the 50mm alot sharper!)
www.pbase.com/jussmith/image/41423507 (http://www.pbase.com/jussmith/image/41423507)

I think that means front focusing, am I right? Is this bad or acceptable?


I then looked at some other shots, this one is the 50mm at f/2.5, 1/200s, ISO 100 and the red dot is the point of focus according to the camera, but this time the bunny seems to be more in focus and is behind the focus point?
www.pbase.com/jussmith/image/41423543 (http://www.pbase.com/jussmith/image/41423543)

Next the turn of my 70-200 f/4 L and the point of focus is the lettering 'R3-42T' which doesn't look sharp. The front tyres also don't, but the rear look better, again contradicting my ruler tests
www.pbase.com/jussmith/image/41423503 (http://www.pbase.com/jussmith/image/41423503)

...and with the 50mm
www.pbase.com/jussmith/image/41423459 (http://www.pbase.com/jussmith/image/41423459)


I've also taken a few of shots 'out in the field' at f/4 with my new 70-200 and cannot find any point of focus behind or in front (worried that there may be a problem with the lens!) or could be that I'm just shaking too much, I need to take some more with better light.


Any comment/help/advice would be extremely appreciated, many thanks in advance.

[roanjohn]

Hmmm.......this doesn't help much. Focus testing can be very trivial..........it seems that you were shooting at 1/15......which is too slow (unless you have a tripod).

However, if you find that one lens tends to have more OOOOF shots than others, it might be worth it to have Canon recalibrate the lens itself.

Also, if you find that all lenses gives OOOFF shots, then it might be the camera.

If a certains lens does it sometimes and not on others, then its probably your technique. On wide apetures, try not to focus and recompose......use the exact focus point to frame your subject and shoot.

NOTE: Also, if you do not have the hack installed, the Rebel will default on AI focus.........which will recompose your focus points when it detects movement.

Ro1

[JusSmith]

Forgot to mention that 50cm on the tape is in line with the box that was used as the focus point! Focus seems to be around the 46-48cm mark.

All shots were taken with a tripod, so AI focus engaging is not an issue.

Do the shots look bad enough for Canon to accept a problem and fix it for me under warranty?

Cheers.

[scottbergerphoto]

Just got myself the 50mm f/1.8 II and after playing found an awful lot of the shots were out of focus. I then looked back at some other shots with other lenses and I'm not quite convinced with these, but then again the apertures are alot smaller.

So I read the threads and did the tests and here are the results.

First the 50mm at f/1.8, 1/80s, ISO 100 (2 feet from subject, focused on 'recomm')
www.pbase.com/jussmith/image/41423508 (http://www.pbase.com/jussmith/image/41423508)

Then the 50mm at f/4, 1/15s, ISO 100
www.pbase.com/jussmith/image/41423509 (http://www.pbase.com/jussmith/image/41423509)

Then a 28-105 at 50mm, f/4, 1/15s, ISO 100 (isn't the 50mm alot sharper!)
www.pbase.com/jussmith/image/41423507 (http://www.pbase.com/jussmith/image/41423507)

I think that means front focusing, am I right? Is this bad or acceptable?


I then looked at some other shots, this one is the 50mm at f/2.5, 1/200s, ISO 100 and the red dot is the point of focus according to the camera, but this time the bunny seems to be more in focus and is behind the focus point?
www.pbase.com/jussmith/image/41423543 (http://www.pbase.com/jussmith/image/41423543)

Next the turn of my 70-200 f/4 L and the point of focus is the lettering 'R3-42T' which doesn't look sharp. The front tyres also don't, but the rear look better, again contradicting my ruler tests
www.pbase.com/jussmith/image/41423503 (http://www.pbase.com/jussmith/image/41423503)

...and with the 50mm
www.pbase.com/jussmith/image/41423459 (http://www.pbase.com/jussmith/image/41423459)


I've also taken a few of shots 'out in the field' at f/4 with my new 70-200 and cannot find any point of focus behind or in front (worried that there may be a problem with the lens!) or could be that I'm just shaking too much, I need to take some more with better light.


Any comment/help/advice would be extremely appreciated, many thanks in advance.
Testing a lens at f/1.8 or 1/15s is a set up to fail. At f/1.8 the lens won't be sharp and the dof is about an inch. At 1/15 without a tripod your making it even worse. In addition the AF area is larger then the focus point so you shouldn't use a 3D target as the camera may be focusing on something other then what you think with more contrast.
Set up a flat target like a newspaper on a wall. Compare shots taken at the same aperture and shutter speed in MF and AF. If the AF is consistently worse then MF you have a problem. Here is a test I did in the past showing how f stop affects dof and picture sharpness with the 50 f/1.4:
http://www.pbase.com/scottbergerphoto/50mm_f_14__focus_test
Scott

[JusSmith]

I did use a tripod and was instructed to do it as wide open as possible. I could't wait for the weekend to see some daylight, hence the slow shutter speeds.