Go Back   Steve's Digicams Forums > Digital SLR and Interchangeable Lens Cameras > Canon EOS dSLR

Thread Tools Search this Thread
Old Jul 1, 2005, 6:13 PM   #1
Junior Member
Join Date: Mar 2005
Posts: 18

I recently purchase the Rebel XT with kit the 18-55mm kit lense. I did an experiment testing the quality of a landscape photo at different f-stops. The image contained a foreground and background mountains a few miles away. I shot all the photos on a tripod. The sharpest photo was at F/10 with the focus on infinity, and is was sharp from foreground to background. At F/22 is was not very sharp throughout the photo, especially in the mountains. I am confused as to why this is the case since the larger the DOF the more range i should have? Please let me know if you have any thoughts.


jpdigi is offline   Reply With Quote
Sponsored Links
Old Jul 2, 2005, 3:06 AM   #2
Super Moderator
peripatetic's Avatar
Join Date: Nov 2004
Posts: 3,599

The APS-C sized sensor on the XT & 20D starts to become diffraction limited below f11, by f22 it's quite noticable.

However you get a greater DOF from the smaller sensor anyway compared to a full-frame sensor or 35mm film, so it's not too bothersome.

You should expect your best performance to be at f8-f11.

If you google "diffraction limitations digital cameras" or something like that you will find a great deal of reading matter.
peripatetic is offline   Reply With Quote
Old Jul 2, 2005, 7:02 PM   #3
Senior Member
Ewok's Avatar
Join Date: Oct 2004
Posts: 142

Also, the results at the extreme ends of a lens's aperture range tend to be less sharp.
Ewok is offline   Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

All times are GMT -5. The time now is 11:24 PM.