I have a focusing issue (at least I think that's what it is) that I'm hoping someone can help me with. I've been shooting lately with the 50D and a Canon 100-400 IS. If I am within 200 yards (rough number) of so of my subject I am able to get tack sharp focus on my images. However, the farther away my subject the less sharp the image. With some subjects all I can tell is that the image isn't sharp, however, with landscape images I can see that there is an area that is tack sharp in front of the area I focused on. Kind of like the camera is front focusing. Would it make any sense for a camera to front focus consistently for long range shots and still be spot-on tack sharp at closer distances. I've noticed this under varying conditions, sunny and cloudy days, and also at night. Any suggestions? I could show some examples if that would be helpful.
If you have any doubt on your equipment will be difficult to make good images. Would suggest to try for yourself and see. Set up a test target and check it. Lens has to be on a firm tripod, target parallel to film plane and can use something printed maybe a newspaper. There are specific targets you can get but no need to go that far.
Distance wise I'm sure you did not mean two hundred yards that is two football fields away which for any bird will be a dot in the frame. Your combo does produce excellent results.
One thing to keep in mind is the total magnification at 400. If you take the camera 1.6X crop factor you are photographing at 640mm and probably hand holding !!! Need to hold steady and lots of shutter speed.
Thanks for the welcome. I did mean 200 yards. I like to use the 400mm for distant landscape scenes where I can isolate just the part that drew my attention. I do use a tripod as well as mirror lock-up. I haven't done tests on newspaper for front or back focusing like I've done on other lenses because the problem is only a great distances.
My bird shots are obviously from much closer than that, and therefore I've had no problem getting them to be tack sharp (no problem other than your typical challenges with birds in flight I should say)
50D/100-400 focus
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