Canon EF 400mm f/4L IS DO II USM

John Sheehy wrote in post #19437064
Better in what way? Did you have to back away from the subject to fit it in the frame?

These aren’t cropped so possibly I could have got away with shooting @400mm, IMO the IQ would be better than with an Extender.

NickR wrote in post #19437085
These aren’t cropped so possibly I could have got away with shooting @400mm, IMO the IQ would be better than with an Extender.

If by "IQ", you mean 1:1 pixel views, or the quality of the entire image, then yes. Any object in the scene, however, is usually better with a TC, if shot from the same distance, with the same shutter speed, and 2x the ISO. The only reasons that I would not use a TC (and crop instead) are reduced AF ability or too narrow of an angle of view to work with.

I used to think that I was paying a big IQ price when using a TC in return for having more pixels-on-subject, and that is certainly how it can seem, but if you do a controlled comparison, a quality TC usually rectifies more problems than it creates, subject-quality-wise, even though the pixel-level and full-image qualities seem to drop. The larger your camera's pixels, and/or the sharper your lens, the more you benefit from a TC.

mikeivan wrote in post #19437111

Hosted photo: posted by mikeivan in
./showthread.php?p=194​37111&i=i114011602
forum: Lens Sample Photo Archive

This from six years ago, Galveston Island. He was close, slightly cropped. I loved my 7dii. For me, the 1.4x extender causes zero IQ loss on the 400DOii. The 2x, not so great. YMMV.

How much of that is because you choose to use the TC more often when the subject is smaller or farther away?

NickR wrote in post #19437085
These aren’t cropped so possibly I could have got away with shooting @400mm, IMO the IQ would be better than with an Extender.

I looked again at the details, and you were at the long end of the zoom, and that is what I based my other reply on. However, if you were working totally within the range that the zoom has without a TC, then you are better off without the TC, not just because of its optical imperfections, but because you actually get a larger entrance pupil wide open when there is no TC (which is also a lower f-ratio in this case), for the same focal length.

A few taken Stanbororough Lakes UK yesterday, great day for photography.

Canon R6 + Canon 400mm F4 DO MKII and @400mm

Grey Heron

Mute Swan

Canon R6 + Canon 400mm F4 DO MKII and @400mm
[GALLERYIMAGE]: embed failed, id not found (image not in gallery any more)

Such a beatiful bird.

Taken with 1.4x TC III

With 1.4X TC III

2loose wrote in post #19442002
With 1.4X TC III

Hosted photo: posted by 2loose in
./showthread.php?p=194​42002&i=i74181733
forum: Lens Sample Photo Archive

Hosted photo: posted by 2loose in
./showthread.php?p=194​42002&i=i249851515
forum: Lens Sample Photo Archive

These are all terrific captures of the red-tailed hawk, 2loose!

Lame-Duck wrote in post #19442033
These are all terrific captures of the red-tailed hawk, 2loose!

Thank you!

With 1.4X TC III.

2loose wrote in post #19453726
With 1.4X TC III.

Hosted photo: posted by 2loose in
./showthread.php?p=194​53726&i=i213416940
forum: Lens Sample Photo Archive

Very nice Peregrine shots, 2loose! This one is my favorite of the two.

I recently picked up a 400/4 DO II. Have yet to give it a fair run, but here is a shot of a backyard Eastern Fox Squirrel taken with the 2x III.

Lame-Duck wrote in post #19453750
Very nice Peregrine shots, 2loose! This one is my favorite of the two.

Thank you!!