I am new to forum, but couldn't find a good answer to my question. I have a Canon 30d (a bit old...I know) and a 24-70 F2.8L and a 70-200 F4.0L lens. Neither lens has IS. I bought the camera in late 2007 and haven't had any problems. Just got back from a vacation where I primarily used the 24-70 lens and some of the photos were a little out of focus. The only issue I have ever had with this lens is that the photos were a little soft when I bought the lens. Sent it back to Canon in 2008 and have had no problems since. To test the lens, I have taken photos of my mailbox at various apertures (2.8, 4.0, 5.6, 8 and 11). I have taken photos at 24, 28 and 70 mm. I also took photos with my 70-200 lens of the same subject at f4, 5.6, 8 and 11. Photos were at 70mm. All photos are slightly out of focus. Comparing the f4 and f11 on the 2 lens at 70 mm, the photos look almost identical at 100%. I also had an old lens 28-135 (F3.5-5.6). Took photos of same subject and compared to photos taken with the 24-70 lens and they looks very similar (24-70 was slightly better which is understandable considering it is an "L" lens).
I was also concerned about front/back focus problem. I lined 5 "AA" batteries on a table at a 45 degree angle to the camera and spot focused on the middle battery. Sharpness of the back vs front battery looked similar.
Are there any other test I can run? I just want to know whether it is a camera or lens issue. If it is the lens I can send it back to Canon and get it repaired. I don't want to get the lenses back and then realize it was the camera. Any thoughts? Would a "bad" camera cause the issues I am seeing.
If you need to see photos let me know. I could probably post them this evening.
Thanks in advance for your help.