Telephoto: Image not sharp in far-focus

Near Infinity Images from my 400mm & over are soft, even with mirror lock-up, gimbal head on a rock solid tripod base, shutter release. Tried leaving IS on & shutting off. Also, used AF & manual focus. (Close & medium range shots are tact sharp) Is atmosphere the problem? Or,does the Canon 20D & 5D electronics create a small amount of vibration? ie. In trying out a lightweight Canon 400mm f/5.6L on a Wimberly Sidekick, and looking through the viewfinder the subject appeared to have minute vibrations at about infinity. Images confirmed some shake. Considering this, I am thinking about devising a support to cradle the entire lens and body during long shots. Any ideas out there?

Hi Pat,
You don't mention the lens model or the shutter speeds you tested. Even with a sturdy tripod and head there will always be some small vibrations but you should be getting consistent results throughout the focal range of your lens. Sounds like your lens needs to go to a Canon service depot to get checked out.

Thanks Ed, I was shooting a bald eagle pair in a nest and first noticed the soft focus problems with the Canon 70-200 f/2.8L IS mounted on an EF 2x (zoomed to 400mm) at near infinity. (I know the 2x doesn't have stellar critiques, but has performs very well at closer ranges.) Plus, my 70-200 f/2.8L IS is normally an amazingly sharp lens. So, I decided to try a prime lens - a 400 f/5.6L. Also used a Tamron 300 2.8 w/2x. I tried several shutter speeds & aperture combinations, set ASA from 100 to 1600. I have used various lenses & 2 different DSLR cameras so don't think it is equipment. That leaves the support system or internal camera vibration or atmosphere or the digital medium as the problem(s). Am I trying to do so much with so little? Hope to swing for the 600 f/4L IS next year. Does anyone have problems with soft images at max focus with the 600mm?

Hi Pat,
If you're getting this problem with several different lenses there could be a camera mount problem. In this case I'd have the combination of the camera body and lens checked out by Canon. I've used some of the combinations you have and I do a lot with my 500 sometimes with the 1.4 or the 2X. I did have focus problems that developed over time and Canon corrected them.

Good luck.

With long lenses, you don't want to use a cable release unless you are using very slow shutter speeds (and in that case, I'd recommend putting a heavy beanbag over the lens). For more normal speeds, you want a hand on the lens, and your face mashed up against the viewfinder, both of which help to damp out vibrations.

-Paul

Thanks guys for the good suggestions. I will try the beanbag & dampening with a hand. Hmmm, I thought hands-off would be better on a tripod. With hand held I cradle the camera with hands & body & mush against my face. I think the 2x is a problem on distance shots. I did test side by side shots with & w/o the extender. The one w/o was better enlarged up 2x in the computer than the one shot with 2x. Now, I need to go find the eagles again.....! Maybe cold clear skies & low wind will also help. If all else fails I will send in to Canon. Regards!!