Ok, So the Ministry of Finance and Home Affairs has given the green light,

But, Which lens.

400 mm F5.6 L Prime or the 100 - 400 mm F4.5 - 5.6 L IS USM or the 300 mm F4 L IS USM ?????

Looking at 'thedigitalpicture.com" ISO 12233 Resolution Chart results, the primes edges out the Tele Zoom, and at around F8 it kills the Tele Zoom.

I will be using this lens mainly to capture my sons new venture into sport, Cricket. I have had some success with my 1D and the 70 - 200 F2.8 + 1.4 Tc but it's still stretched. It will also be one of my go to lenses with Rugby in the winter, with my 70 - 200 on the 50D.

I like the idea of the 300 mm F4 L USM for the IS and that goes with the 100 - 400? but all the research points the Prime/s has/have the better IQ.

I would also like to have a crack at birding, so the 400 mm F 5.6 L USM Prime rings the bells there.

The 300 mm F4 + 1.4 Tc is also an option, especially on the 50D, do the maths and that's some EFOV reach. 420 mm @ F5.6 + IS ???? with out 1.6 crop factor.

Arrrrrgggghhhh - Which way to go, heart says the 300 mm F4 (As I have used this and loved the handheld slow shutter speeds available with IS) but the brain says the Prime 400 mm for the obvious reach. I don't think I'll use the 100 - 400 full range, the minimal focal distance is much the same as the prime 400, Higher ISO and faster shutter speeds in good lighting conditions is what the lens will mostly be used in???? If the 400 mm F5.6 Prime had IS - Job done.

70 - 200 mm + 1.4 Tc = 280 mm This is what I've got at F4,

300 mm + 1.4 = 420 mm @ F5.6 + IS - True focal length,

400 mm F5.6 L as is.

Thoughts or suggestions appreciated.