need help with a big lens

I have a cheap third party 100-400 F4.5-6.7 lens. Unfortunatly cant afford a canon in that range I have a canon 100-300 usm lens that I have got exellent shots from and got this for that little bit of extra reach. I mainly will shoot wildlife with it as its not fast enough for anything like sport. What I need to know is what kind of settings on a clear day work best for this kind of lens? I have not got much in the way of a good shot out of it at 400m yet. Im not expecting wonderful sharp shots of course with it wide open, however I cant seem to get a reasonable shot at this focal length at all Its not too bad at 100 to 250 though. any advise on any way to improve the use of this lens would be appreciated

If you are trying to hand hold the lens simply get either a monopod or a tripod or both. These will pay you back many times in image quality on a long lens.

What are the shutter speeds you're using at the longer focal lengths? Long lenses require high shutter speeds unless you're using a tripod. At 400mm on a 300D, you're looking at 1/500s or higher to have a good shot at getting sharp photos. I would also imagine that a cheap lens (especially one that's that slow at the long end) needs to be stopped down to f/8 or f/10 to get good sharpness, which puts further difficulties on shutter speed. If it's still very soft at f/11 tripod mounted, I'd say there's nothing you can do to improve the shots...it's just a weak lens.

The really long focal lengths are expensive to get quality glass. There are several decent budget options that go to 300mm, but 400-500mm you're looking at around $950 (Sigma 50-500) to really get something decent.

If you're getting good results with the Canon 100-300 then you're probably getting what you paid for with the cheapo 100-400. Cheap zooms are often poor at their long end. Even mid-priced Canon zooms are not that good fully extended (like my 75-300 IS). If you're going to keep the 100-300 it might be worth saving for a reasonable 400 Prime.

This is going to sound stupid, but I was under the impression that if the lens range is 4.5 to 6.7 that I could not shoot at F11 or anything over 6.7????

No....that's the maximum aperture of your lens. So, at 100mm, you have a maxium aperture of f/4.5, and at 400mm you have a maximum aperture of f/6.7. Your minimum aperture is probably at least f/22 (remember, larger numbers, smaller hole). I've never seen a standard 35mm SLR lens that doesn't go to at least f/22. I know there are some specialty lenses that might only close down to f/16, and a few mirror lenses with fixed apertures of f/8 or so (unchangable), but other than that you will be able to close down the aperture to a smaller number.

This explains a lot...you're shooting with a cheap lens, at it's focal extreme, wide open. Stop that thing down, use a tripod, and you'll probably see a large improvement.

Thanks, Im such a dill,:o I was thinking it was like a mirror lens. I never even thought of it. Mind you Ive only had it one day Had the camera set on TV and was going by shutter speed only, then tried AV at F 6.7, will try it out tommorow.

It is however important to remember to use a fast enough shutter speed if you're not using a tripod. If you're using the "Creative" zone (letters) settings, you can use a higher ISO number to let you get better shutter speed and aperture. If you're in one of the "Basic" (pictures & green box) zones, the camera won't let you set this (among lots of other things). At the long end, you should have a shutter speed of around 1/600 or faster. THis virtually guarantees you'll need ISO 800 on a sunny day if you want to hand-hold at a good aperture (f/11) when at maximum zoom.