Crop from full frame or use 1.4 TC

[David Cowling]

I am using the Canon 5D Mk4 mounted with a Canon 400mm f5.6 L lens ( as much as I want to carry nowadays}. My question is: Would it be better IQ wise to crop the image as opposed to using the 1.4 mk 2 TC. Although I love the 5D Mk4 I miss the 1.6 crop of the 7D mk2. The problem we have in the UK is that generally we are not able to get as close to birds as you seem to in the US. My thinking is that by using a TC I would be getting more pixels on the bird if it were some distance off; the trade off being a slight loss of IQ.
Regarding the 1.4 TC I have read that the Mk3 1.4 will allow more focus points at f8 than the mk2 on this camera body. If this is the case would it be worth my money to get a MK3 1.4?
Thanks in advance.

[arash_hazeghi]

with the 5D4 AF all the AF points can work at f/8 but it depends on the lens and the vintage of the TC. The problem is that the lens you are using will not yield acceptable IQ with any TC. If you just want to use it for casual shots it is OK but if you are after anything of quality it would be a waste of time plus the AF will take a big hit by adding a TC to this lens.

best

[David Cowling]

I hear what you are saying about lenses Arash but unfortunatly all the money trees around here got blown down in the last gale - that's a joke! The real reason I am using that lens is that it is the lightest L lens around, and at 79 I don't want anything too heavy. I have seen great images made with that lens. I had the 100-400 Mk2 but sold it because of the weight but I think the prime is just as sharp. From your reply I guess the answer is to crop, fortunatly the 5D Mk4 has plenty of pixels for that. Thanks for the input.

[arash_hazeghi]

Hi David, I think sharp is subjective, if you find the old prime as sharp as the new zoom you might actually like what you get with the TC too so give it a shot.

Best