Hi Robert,
I do understand about testing, I do a ton of it myself to understand the limits of my gear before I get in a critical situation. The second two photos you posted are much better, though I have no point of reference as to how much of the frame the subject filled and if/how much cropping was done compared to the first image you posted...and that makes a huge difference, of course.
I recently posted to another thread regarding the 600pf and how surprised I was by a couple shots I took, not so much as a test, but to identify a chattering bird in the top of a tree a considerable distance away. The bird only occupied about 745 vertical pixels out of the 5504 or about 14% of the vertical frame. Normally, I'd walk away from this shot, but the atmospheric and lighting conditions were just about perfect and the resulting image is totally fine for social media or typical online viewing. Would I print it...with some begging or a bottle of wine, maybe...lol
You never know with March weather. 50's last week, 50's next week... snow today. For some reason, my uploaded shots are looking pretty mushy. How's this one look to everyone?
bcgforums.com
I didn't post this image in the other forum post, but here is one of the images cropped from 8256 x 5504 to 1118 x 745 pixels (.8MP) or 4444mm equivalent focal length. I notice after previewing this post that the forum software seems to be scaling this up to fit the default page width, so on this site one will be viewing at close to 200% on a 4K display, so may look softer than it really is unless viewing on a 1920 x1080 display.
View attachment 87637
As for my preference for cropping over a TC, that has often been dictated by the quality of the TC and the camera body I'm using. I was much more inclined to use a TC on my previous D850 and D500 as on a DSLR, I did not like shooting in DX mode and trying to compose with the smaller image in the viewfinder. I own the 1.4x and 1.7x, f-mount TC's that I've had for years and they were reasonably good and had their place. Mostly they were used on a 300 f2.8 VRII, 500pf and 70-200 f2.8E FL and they 1.4x was very good on those specific lenses. The 1.7x was the first TC I bought and was hit and miss, depending on the lens I used it on. I'd be curious to see some tests with your setup of reasonably controlled comparisons of crop vs TC, though I understand that you're not starting out with as many pixels
Now with mirrorless I can shoot in DX mode and have a full image in the VF...and at times, there are advantages to "Cropping in the camera body" as opposed to cropping in post in terms of AF performance or speed. Now with mirrorless bodies, Z9 and Z8, and both 45MP, I do have the Z TC1.4X and it's substantially better than the f-mount models. I use it occasionally under the right conditions on my 100-400 or 600pf, but generally I'll just crop or use DX mode...or both.
Totally agree with keeping filters and such off the front of my lenses unless for specific uses...variable ND for video or CPL's as needed...have had too many issues with flare or other artifacts, even with high quality filters.
Enjoy your upcoming Darwin trip! I hope to get down under there sometime before I get too old to enjoy it...I better hop to it!
Cheers!