I've been shooting boat races with a 1Dmkll and a 70-200 is F4 lens. I'm using 200mm all the time and still have to crop them close to 100%. I'm thinking about getting a 300 F2.8, or a 1Ds MKll(16 mega-pixel). Is it better to get a longer lens or more pixels? I love my 70-200, it's very sharp even at 200mm.

Thanks for the any thoughts,
Rob

The 300f2.8 is insanely nice.

If you're shooting from a boat, any 300 is an SOB to handle. If from shore, it's not such an issue.

I'm wondering why you need the 2.8. Limiting DOF is one thing, but the jump in IQ over an f4 version simply isn't worth the price difference. I've got both in the Nikon line, and I only bother with the 2.8 when I need to hold down DOF.

Next question, depending on the magnitude of your current crops, would a 400 make more sense? If you're not chasing your tail on the light issue, a 5.6 won't break the bank.

Under the circumstances, I would buy a Canon 300mm f/4 IS lens for this application. In my experience, it's better to use a longer lens than to crop a higher-megapixel image. The 300/4 is small, light, and insanely sharp.

If you don't need S resolution, you could always just get a 40D and one of the smaller aperture IS zooms that reach 300mm. That would give you more crop-free magnification, and cost a lot less than either of your other options. I assume a lot of boat races are conducted in bright light, where you could probably use smaller apertures than 2.8 to no ill effect. Something like the 70-300 DO IS might be fun, since it is far more compact than any 300 prime.

The downside would be a dimmer viewfinder, and less sealing protection from the water. The 40D combo would be so much cheaper that you could afford to replace two or three that were ruined by spray, and still be ahead.

But then again:

Another possibility is to buy a Canon EF 1.4x II Extender to go to 280mm using your 70-200. Inexpensive, but you lose one stop and it may not be enough zoom gain to meet your objectives. On the other hand, if 280mm focal length is not sufficient, then 300 is probably not either and you may need to go to 400.

The EF 2.0x II Extender would get you to 400mm with your 70-200, however it apparently suffers from loss of resolution.