300 f/4 IS + 1.4x vs. 400 f/5.6 on crop sensor

[djzuk]

I'm curious to know what the IQ differences are between these two options when using a crop sensor camera such as the 20D with 8MP. Does anybody have both of these lenses with an extender? The IQ differences when on the 1Ds Mark III are clear; 400 prime wins in sharpness hands down. Will the differences be similar when using a 20D? Or will it not be noticeable?





Thanks,
Derrick

[Brendan7]

The 400 will win in image quality no matter what you mount it on. However, the 300 w/ TC will give you IS.

[neuroanatomist]

If you will mount it on a tripod, the 400mm. If you need to hand-hold it, 300mm + 1.4 TC. The better IQ of the 400mm will not help if you've got shake-induced blur.