First attempt at photographing birds with R, and a question about lenses

I got mine for a steal (around $550 used, Amazon, like new)... I did end up returning it.

Why:

Front heavy with the adapter. Despite being the lightest 100-400 on the market, with that adapter, it'll get heavy really fast. It's not just the weight, it's how it handles. I have no problem with a 28-70 f/2L, but a 100-400 adapted? Yup.

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AF accuracy is 100%. AF speed though, is not. Very slow. It also has trouble with macro and infinity focus swaps and gets confused requiring intervention ie focusing on something intermediary length, or a manual focus pull to resolve.

Image quality is high, especially for the price, weight. SOOC JPEGs above (uncorrected, note vignette). Color is good, bokeh is good, contrast is good. In the end, like you, handling/weight is a big deal. Oddly things like this handled better on my former M6 II, where you held the weight from the lens almost entirely, vs on the R, you hold it from the camera while supporting the lens. Try for yourself but you've been notified if you're looking for a lighter solution, it is, but it doesn't help. It's still an excellent option if that's not your goal, and the bang for buck is phenomenal.

BTW, I'll add, there is still a strong case for this type of photography to happen on a dense crop sensor, be it the M6 Mark II or 90D, where you can't beat the pixel density otherwise cropped. This is a strength of crop bodies (reach).

Oh, one more thought... Those new 600 and 800 DO lenses, mesh with teleconverters. That's a good use of an R for reach purposes, and light, cheap, for what they are.

https://j.mp/36mD86V

$700 USD, and the same size as the 100-400, but with 200mm more reach... And, can tele convert. And, lighter... You get the picture

Too bad no DO for EF-M Canon did have patents for it, so it was considered, but rejected, in the form of a patent...