R5+100-500+1.4x or R7+100-500?

RDM5546 wrote:

TimP111 wrote:

would be surprising if the R7 out resolves the R5.. ofc it doesnt

You are right that with slight cropping and good sharp lens the R5 wins but this issue is about extreme cropping where is not possible possible to get closer to the subject like you experience in skittish wildlife.

At some degree of cropping the higher pixel density on the image circle wins. The APS-C 1.6X crop covers 1/2.56=.391 (39%) of the FF sensor with 72% of the 45MP of the R5. The APS-C sensor of the R7 has 84% more pixels as the FF camera put on the this part of the center image. The center image image pixels of the R5 will have less noise resulting from the bigger but fewer pixels.

The best 1" sensors have less high-ISO noise than a 1" (2.7x) crop from the R6.  The R7 has less noise than a 1.6x crop from the R5.  You are likely to NOTICE the noise more with the R7 due to higher magnification at 1:1 pixel view, and the gratuitous pixel-level sharpening almost always applied to the R7 by default in converters, which is sharpening a frequency not even present with larger pixels.

The use of TC will reduce the aperture size of the R5 images and that aperture size reduction the R7 does not experience (f7.1 for the R7 and f10 for the R5/1.4X case and f14 for the R5/2X case). Diffraction effects will pay a bigger role using the 2X extender.

Not under the conditions stated, for focal-length-limited photography.  TCs do not affect the size of the diffraction blur relative to the subject, when shot from a distance, because the TC does not change the maximum pupil size, which stays the same with both TCs and crop factors.  If you put on a 2x TC and step back twice as far from the subject, THEN the diffraction blur will be larger relative to the subject size.