I disagree, my friend has the Sony A1 and the excellent Sony 200-600 and he gets pretty much identical image quality to me with my R6ii and 200-800 his high MP and my extra magnification make for very similar results when he crops in to match my FOV.
Yes, that is what would be expected to happen when the 200-800 doesn't add any additional resolving power beyond about 640mm. You get a bigger image, but no more detail. So when your friend crops his 600mm image to emulate the FOV of your 800mm image, you get roughly the same image quality. It's also why the 200-800 starts looking a little soft as you go further past 600mm. Image gets bigger but no further detail can be resolved.
Ultimately in the end there are no free lunches. Sony did it "right" with their 400-800 but it's bigger, heavier, more expensive, and starts from 400mm. Canon opted instead to make a smaller, lighter, less expensive lens that starts from 200mm but that has come at the cost of optical performance on the long end.
And, if you would like to compare the difference, ask your friend to rent the 400-800 for a few days, then compare the images.
Upvote
0




