nick0954 wrote:
Dustin Abbott just released his 600 F6.3 GM review. I thought this was an interesting comparison that I was able to make by downloading some of his test chart images.
Looks to me that the 400 F4.5 + 1.4x TC is at worst indistinguishable, and most likely slightly sharper with better contrast, from the 600 F6.3 bare lens. The bare 400 F4.5 looks sharper than the bare 600 F6.3. This makes sense given the optical similarity of the lenses.
Where this falls apart is that the 400 + 2x TC is massively worse than the 600 + 1.4x TC, which was slightly surprising to me. Both lenses frankly look bad with the 2x TC. So the question is really do you want a 400/560 or a 600/840?
Personally, I'm still torn between 100-400 F4.5 + 600 F6.3 or just rolling with a 400 F4.5 + 1.4 TC for my telephoto needs for now. But this makes a compelling case to start with the 400 F4.5 and keep my 70-200 GM II and see how far those 2 lenses + TCs as needed gets me.
Slight correction on your comment : >>So the question is really do you want a 400/560 or a 600/840?<< It more accurately should read, do you want a 400/4.5 and 560/6.3, or a 600/6.3 and an 840/9?
Which is the rub for me... Aperture becomes significant enough with the 1.4 on the 600 for 840/9 to consider it a marginal use option, while 400/4.5 is definitely an attractive option, while 560 vs 600 with both at f6.3 becomes mox-nix.
F8 on the 400-800 was already a bit marginal for me, f 9 more so. In which case since I already own the 1.4x would probably spring for the 400, and use it with the 1.4x in APSC mode as a casual, lower rez 900-ish at f6.3 birding option... I also think Sony missed an opportunity to build a 1.4x converter into the 400/4.5 -- it would have been an ideal quick-switch mammal lens.
nick0954 wrote:
Dustin Abbott just released his 600 F6.3 GM review. I thought this was an interesting comparison that I was able to make by downloading some of his test chart images.
Looks to me that the 400 F4.5 + 1.4x TC is at worst indistinguishable, and most likely slightly sharper with better contrast, from the 600 F6.3 bare lens. The bare 400 F4.5 looks sharper than the bare 600 F6.3. This makes sense given the optical similarity of the lenses.
Where this falls apart is that the 400 + 2x TC is massively worse than the 600 + 1.4x TC, which was slightly surprising to me. Both lenses frankly look bad with the 2x TC. So the question is really do you want a 400/560 or a 600/840?
Personally, I'm still torn between 100-400 F4.5 + 600 F6.3 or just rolling with a 400 F4.5 + 1.4 TC for my telephoto needs for now. But this makes a compelling case to start with the 400 F4.5 and keep my 70-200 GM II and see how far those 2 lenses + TCs as needed gets me.
Slight correction: >>So the question is really do you want a 400/560 or a 600/840?<< should be do you want a 400/4.5 and 560/6.3, or a 600/6.3 and an 840/9?
Sep 18, 2026 at 02:01 PM
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