# Thread: Nikkor T ED lenses: 600/800 vs. 600/800/1200

1. ## Re: Nikkor T ED lenses: 600/800 vs. 600/800/1200

you need a 650mm image circle for 16X20. The image circle for the 600/800/1200 is 310mm @ ƒ22 (for all the focal lengths), so you'd need to be focused fairly closely to even come close to covering. the FFD for the 600mm at infinity is 409mm from the film. with a little triangle math it looks like the lens would need to be 857mm from the film to throw a 650mm image circle. I'm not sure how to calculate how close that would be, but presumably it would be closer than 1:1.

2. ## Re: Nikkor T ED lenses: 600/800 vs. 600/800/1200

Originally Posted by abruzzi
you need a 650mm image circle for 16X20. The image circle for the 600/800/1200 is 310mm @ ƒ22 (for all the focal lengths), so you'd need to be focused fairly closely to even come close to covering. the FFD for the 600mm at infinity is 409mm from the film. with a little triangle math it looks like the lens would need to be 857mm from the film to throw a 650mm image circle. I'm not sure how to calculate how close that would be, but presumably it would be closer than 1:1.
Nikon's specs are defined by the shortest focal length, not by the whole set. The rear elements are designed in a comparable way to teleconverters, where the FL is increased by magnifying the image circle by 1.4x or 2x (cf also focal reduces by Metabones, where the focal length is reduced by .71x and the *relative* aperture is increased accordingly, both with a smaller image circle.). I shoot the 800mm on 11x14 regularly with great satisfaction.

And there was a great thread recently about the coverage of the Nikon 720mm element of the 360mm f8/500mm f11/720mm f16 set that showed how effectively the 720mm combination covers 8x10:
https://www.largeformatphotography.i...=1#post1657576

Now, whether the 1200mm could cover 16x20? That's a different story. Maybe? Or maybe not. I'd love to see that test.

3. ## Re: Nikkor T ED lenses: 600/800 vs. 600/800/1200

As someone who shoots 12x20 and has the 1200mm rear element for this lens, no, it doesn't cover even 12x20, let alone 16x20. At infinity focus and narrow apertures, the hard limit of coverage on my copy seems to be about 10x20. I use it on 11x14 without a problem.

4. ## Re: Nikkor T ED lenses: 600/800 vs. 600/800/1200

Originally Posted by senash
As someone who shoots 12x20 and has the 1200mm rear element for this lens, no, it doesn't cover even 12x20, let alone 16x20. At infinity focus and narrow apertures, the hard limit of coverage on my copy seems to be about 10x20. I use it on 11x14 without a problem.
Thanks for the confirmation!. I'd love to have the 1200mm rear group for my 11x14.

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