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

drsnoopy wrote:

I have the R5 and 100-500, and very happy with the combination. I also have an R7 on order but now I'm wondering whether anyone has done a comparison between the R5 with the 1.4xTC (giving 700mm max FL) and the r7 with the bare lens (giving 800mm effective max FL). I do understand the issue with the TC restricting the short end of the zoom range. I've also tried crop mode on the R5 (17MP) and the results are mostly good but would like the extra sensor resolution. My feeling is that the r7 should have the edge, bearing in mind of course the differences in noise, which I am happy to deal with in RAW conversion (DXO) or in post (Topaz). However the TC would be less expensive...

Thanks for any examples or pointers towards other sources.

From any given distance, you will put almost exactly the same pixels on the subject at any zoom position, because the difference in pixel spacing with the two sensors is about 1.36x, very close to the TC magnification.  Since this is true, it is fair to compare pixel-level noise, and the R5 has more pixel-level noise at 2x the ISO, plus, the extra aberration from the TC, even if small, makes the captured detail punch less through the noise at the pixel level.  However, the R5 will have a slightly wider angle of view to aid in visual tracking, and the e-shutter will roll through the subject about 2.3x as fast with the R5.  The R5's AA filter is less prone to color moiré at the pixel level.

You would likely only use both at the same physical zoom position when you are at the long end, because if you zoom out, the two different sensor sizes will give different angles of view when you aren't in "forced crop" mode at the long end.  If you chose to remove the TC in such a situation, you are better off with the R5 in almost every way, if you want to use the largest pupil possible.  If you leave the TC on and just back out as far as you can, most of that benefit would not exist, as zooming out with an unnecessary TC gives you a smaller pupil at any given angle of view.

I believe that I have already graphed what pupils you get over their ranges of angle of view for all three combos mentioned (APS-C, FF, FFx1.4), I have posted it in the past and it is on my other computer.  I'll look for it.

So, if you were hoping for a simple answer, you won't get one from me, but if one is speculating about such things, always think about the pupil; the pupil is the core of imaging with a lens.