RF extender experiences with RF 100-500 1.4x vs 2.0? Locked

frostybe3r wrote:

Speaking of TC's, my R5 + 500mm f/4 L IS II USM + EF 1.4X III detail is ridiculously good.

But I guess that's not comparable to an RF 100-500 and FYI, I don't consider the RF 100-500 or most zooms to be ideal with teleconverters, sure, the results are okay but sometimes it's just better to crop, you're now shooting at what? f10?

F/11 is irrelevant, unless the light levels are extremely low, and that is covered in my qualifications about having sufficient AF ability.  Otherwise, what matters is the size of the pupil, which is the same as without the TC, AOTBE.  If the noise makes it not worth taking the photo with the TC, it also makes it not worth taking the photo without the TC, and cropping instead.  You can't take the IQ of an entire frame down into a crop.

Once again, the real issue is that your subject is small and/or distant (or light is poor).  You might be able to have a larger aperture lens, but the TC itself or the resulting f-ratio is not the cause of more noise; it is your main lens and the lighting and distance situation.

How much ISO do you now need to compensate in a lowly lit area, under trees, in shadows, in the evening?

About the same as the subject now covers more pixels, so about the same subject noise.

Yes new cameras have good ISO capabilities however, the R5 still isn't the 1DX in terms of low light

The difference is smaller if you break away from the 100% pixel views.  Anyway, the question here is not 1Dx vs R5; the question is, if you get the focus that you need, does the TC give you worse, the same, or better results, normalized to the subject size?

and you will see a hit on sharpness due to your bumping up ISO high, but if you need that reach and still get the shot, that's great.

You don't seem to understand how to scale things in your mental models; you're looking at pixels, while the subject quadruples in area.  Using a faster shutter speed may increase the subject-level or the level of noise at any level of subject detail, but using a TC and raising the ISO with the same shutter speed has subject details sizes increasing in pixels, while the pixel-level noise rises.  Using a TC does have less returns at the very highest ISOs, but for many intermediate ones, the TC gets more, better-sampled subject detail.