I have a 100-400L 5.6 .(Hey, it was a gift) I added a 2xextender and since the automatic focus doesn't work, I have to hand focus. I'm having trouble getting a really sharp result even with a tripod and shutter delay. Trying to take birds, on a feeder, not far away(40') so would be real close up. Seems like the slightest move will create unfixable blur. Is there some trick here? Also, the canon book says this lens should do f9, but it hasn't gone lower than 11. If there isn't real bright sun, the shutter speed is so slow, almost impossible to keep a focus. Anyway, any ideas, or is it just me.
Thanks much.
Greg

ps, sorry- it's a dig rebel, 300D

Greg, it seems like you're trying to set up a very tricky shot. Assuming you're using the 400mm end of the zoom, the 2x and the 1.6 crop factor of the Rebel is yielding you a 1280mm lens! If that wasn't difficult enough, you're shooting way close (40') and slow (f/11 at best). This is a non-stabilized lens? At those conditions, your tripod will need legs like trees and you won't be able to breathe anywhere near the camera during the release.

Try this test: on a very bright day, shoot at something in the far, far distance (a bright car, reflection off a building) and see if your images are any better. If not, perhaps this combo just wasn't meant to be.

By the way, if the DRebel has mirror lock up, engage that for the test and use the self timer to minimize any internal vibrations.

Loupey summed it up pretty good. That lens, with a 2x TC is a pretty slow combination. I'm in the same boat with my 500mm and 2x TC. If you haven't tried it yet, boost your ISO. I have the same camera and I hate going over ISO 400, but you have to do what you have to do to get the shutter speed that you need.

The DRebel doesn't have mirror lockup, but a remote shutter release is a good investment if you don't already have one. Then you can take the pic when you want, and not have to wait for the timer.

What are you using for a TC? The quality of the optics plays a big part in this as well. My 500mm lens can be pretty sharp when I hit the sweet spot, but when I add my cheap Quantary 2x TC to it, I might as well be shooting thru a dirty window. You can try to stop down your lens to get to the "sweet spot" but this will cause even slower shutter speeds, but worth a try if you have good light.

I have a 100-400L 5.6 .(Hey, it was a gift) I added a 2xextender and since the automatic focus doesn't work, I have to hand focus. I'm having trouble getting a really sharp result even with a tripod and shutter delay. Trying to take birds, on a feeder, not far away(40') so would be real close up. Seems like the slightest move will create unfixable blur. Is there some trick here? Also, the canon book says this lens should do f9, but it hasn't gone lower than 11. If there isn't real bright sun, the shutter speed is so slow, almost impossible to keep a focus. Anyway, any ideas, or is it just me.
Thanks much.
Greg

With no mirror lockup you may have a problem. George Lepp routinely used two Canon 1.4 extenders at the same time (!) on this lens and got fanstastic images. Are you using a heavy rock solid tripod? Try adding weight to it.

As a combo with an effective focal length of 1280mm, I rate that as a telescope instead of a telephoto. So if you do photograph over great distances, you're going to see atmospheric distortion (which can be a good thing at times). So for testing, shoot in bright, clear, daylight.

The 100-400 is f5.6 at the long end, adding the converter takes another two stops.
You are beyond the limit of the camera's AF system so you have to manual focus.