lenses

hello out there !!!

i'm new to photography and this site so forgive me if i sound like i don't know what i'm doing or talking about...
i need some advice:

i've got a nikon D50 and i shoot surf photography from the beach (surfers are approx. anywhere from 60-80 yards out, maybe even a football field length)...
anyway, i use a 70-300mm lens with a 2x converter...i'm usually going from 200 to 300 mm (maximum zoom) with the lens, and with the 2x converter it makes it 600 mm...
anyway, my pictures come out soft, not as sharp as i'd like...i'm assuming it's because of the 2x converter and the zoom...

my question is this:
my subjects come out large enough (i would like to even zoom in a little more if i could), but the subject is soft...what kind of lens (mm-wise) would i need to make subjects come out sharper and closer?
Also, after getting the photo into my computer, i'll crop it to make the subject look bigger, but how do i know how big my print can be?? i'm thinking that by cropping, the print will come out grainy if i go big (8-1/2x11 or even 20x30).

i don't have the cash to spend BIG bucks on a spectacular lens (who does unless you work for Sports Illustrated and they buy your lens for you)...
will a 400-500 mm lens work and then i just crop my photo without it getting grainy when enlarged???

your advice/help is greatly appreciated////

I'm betting your 'soft' issue is due to focusing and motion issues. The 70-300mm I believe is f/5.6 or 6.3 on the long end, and then you lose another stop or two with the teleconverter. This will make focusing tuff for the camera, and then add on top of that the fact that your subject is constantly moving adding another tuff focusing situation. Also because your largest aperature is now f/8 or so, that makes it tuff to use a shutter speed fast enough to freeze the action and also means handholding the camera is out of the question (it should be out of the question anyways at those focal lengths). You can increase the ISO to compensate but you'll get more noise which if you do larger prints will become a problem as well.

So... Use a tripod and use the fastest lens (smalles f/ number) you can to achieve a decent shutter speed. Try prefocusing the camera to a specific spot and just waiting until the surfer gets to that spot and snap the picture at that time. The thing with that though is that the peak moment of action may not happen at the distance that you're prefocused at.

so this 300mm (600mm) with the 2x converter is enough lens?
i do shoot with a tri-pod, and usually only when the lighting is excellent.
i know the 2x converter makes it soft...will a 50-500mm lens (no teleconverter) be enough zoom for me to make the subject a decent size?
what about the cropping part of it to make the subject bigger in the print? also enlarging the print to 8-1/2x11 ???

Whether or not the 50-500 (I'm guessing the Sigma) is good enough is up to you. I would take the 300mm with 2x teleconverter and set it the lens to 250mm and shoot with that for a day. If you find your results are acceptable without extensive cropping then the 50-500mm will work. If you find you have to crop a lot maybe not. For 8x10 printing you should have some cropping room with the D50 to get acceptable prints. I try to leave roughly 300ppi if possible, though I've seen acceptable work at 250-200..

took your advice and shot with the 2x extender & the lens on 250 & 200 mm.
i found that i do have to crop a lot and my final picture is just starting to get a little grainy -
not much but you can tell the degregation.

yes, the 500mm i was lookin into is the sigma.
what do you know about mirror lenses?
there's a quantaray 500mm (fixed) w/macro but the f-stop is already @ 8.0
is it true that if i put the 2x on this that i would lose another f-stop (9.something)?
is mirror that much worse than glass?

Avoid mirrors like the plague. Everything that is out of focus will look like little donuts which is very distracting. If you attach the 2x converter to the mirror you are losing 2 stops of light. 2 stops from 8=16. F/16 is too small an aperture for that kind of shooting and you will probably never get a fast enough shutter speed to stop the action.

Z