Sony a 9

[ricktas]

Rick, I pointed out to you that the correct comparison would be 50m and 100m. The only response you could come up with was "So you want a wildlife photographer to move 50 metres, and possible spook their subject?". That was just trying to be clever.
If you want to compare 2 different lens lengths, then you would compare them with the same sized subject in the frame. So a 200mm at 50m would give you he same sized subject as a 400mm at 100m. Would it not? Of course, 10m or 20m would be a better comparison (or for bird photography, 2 or 4 metres).
Anyway, you are right, this is pointless. So you may as well remove me.

I was not trying to be clever, but be factual. Your original comparison made no mention of varying distance to subject, so I wanted to clarify that. I did so using a DOF comparison. Then after my post, you added the addition distance variance.

I merely pointed out that if you are shooting some wildlife and said wildlife is 50 metres from you, that whether you choose the 200 @ f2.8 or the 400 @ f5,6 (the settings you said) the resultant DOF etc is different and thus the resultant photo will be different.

So whichever one you choose (with distance to subject being the same) is going to affect the resultant image. I was not posting for your benefit, I was doing so to clarify your original comparison, for anyone else reading the thread (beginners perhaps?), who from your post, may have assumed that 200mm @ f2.8 and 400mm and f5.6 would produce the same result. Field of view and subject size may be the same, but other factors (DOF included) will mean the image will not be the same.

Unfortunately you seem to think factual additions to a thread are not warranted and simply someone trying to be clever.