# Thread: 890mm APO NIKKOR IMAGE CIRCLE @ 1:1 & INFINITY

1. ## 890mm APO NIKKOR IMAGE CIRCLE @ 1:1 & INFINITY

I've just purchased an 890mm Apo Nikkor f11 for a song that I want to experiment with LARGE paper negatives etc. I realise that these process lenses were designed and corrected for 1:1 work, and I've read the scores of arguments about whether they are sharp at infinity. I also discovered an entertaining read in regards to the 'flat field myth', where the discussion about flat and curved field designs really make a difference. It seems that many people are using the Apos in the field with success.

Can anyone tell me what the projected image size for one of these would be at 1:1 and infinity...I'm hoping to get larger than 24" square? Has anyone got any first-hand experience with one that they might share?

2. ## Re: 890mm APO NIKKOR IMAGE CIRCLE @ 1:1 & INFINITY

Learn to use the forum's search function.

Learn how to calculate circle covered's diameter from angle covered. Apo-Nikkor angles covered are here: http://www.galerie-photo.com/apo-pro...ikkors-en.html

The diameter of the circle covered at 1:1 is twice the diameter of the circle covered at infinity. Angle covered is the same.

3. ## Re: 890mm APO NIKKOR IMAGE CIRCLE @ 1:1 & INFINITY

I did use the search function...it's how I got the information I mentioned in the original post.

Your link was excellent though because it gave me the angle of coverage as 42 degrees. So I can then calculate:
Coverage = 2x(Focal length x tan (1/2 angle of coverage)
2x(890mm x tan (42/2)
= 683mm (27")
So at 1:1, I should be getting approximately a 54" diameter image circle (correct me if I'm wrong )

4. ## Re: 890mm APO NIKKOR IMAGE CIRCLE @ 1:1 & INFINITY

You may find this calculator handy. http://imaginatorium.org/stuff/angle.htm

5. ## Re: 890mm APO NIKKOR IMAGE CIRCLE @ 1:1 & INFINITY

Originally Posted by Craig Tuffin
I did use the search function...it's how I got the information I mentioned in the original posthttp://www.largeformatphotography.info/forum/showthread.php?86484-Apo-and-Process-Nikkor-info&highlight=apo-nikkor
That's interesting. This http://www.largeformatphotography.in...ght=apo-nikkor is the 28th link returned by a search on apo-nikkor. That is, it is on the first page returned. You may have tried something cuter.

6. ## Re: 890mm APO NIKKOR IMAGE CIRCLE @ 1:1 & INFINITY

But you left out the variable of the f/stop itself. The "official" angle of view on a process
lens is probably at f/22, though there are exceptions. But at the smaller stops likely to be
used in the field, the image circle is going to be considerably larger. I can't give you a specific answer. The longest Apo Nikkor I own is 760 and I have never field tested it yet.

7. ## Re: 890mm APO NIKKOR IMAGE CIRCLE @ 1:1 & INFINITY

Originally Posted by Drew Wiley
But you left out the variable of the f/stop itself. The "official" angle of view on a process
lens is probably at f/22, though there are exceptions. But at the smaller stops likely to be
used in the field, the image circle is going to be considerably larger. I can't give you a specific answer. The longest Apo Nikkor I own is 760 and I have never field tested it yet.
Thanks Drew, very much appreciated!

With f11 as it's widest aperture I was going to stop it down 2 to 3 stops (as it suggested in Dan Fromms article ) and do some tests, so f22 sounds great. I will be shooting with the lens wide open for some 1:1 portraits so it will be interesting to see what I can get.

Cheers for the help guys!

8. ## Re: 890mm APO NIKKOR IMAGE CIRCLE @ 1:1 & INFINITY

I only use 4-4 dialyte process lenses in shorter lengths (240-480 mm) but unlike, say, plasmats or their Celor-derived cousins they don't gain very much image circle when stopping down. Older ones will illuminate a nice big plate because they lack the field stops of modern versions, but if you want sharp definition into the corners at infinity reckon on them covering their focal length at best.

9. ## Re: 890mm APO NIKKOR IMAGE CIRCLE @ 1:1 & INFINITY

Thanks for your help everyone but on another note (but still in regards to this lens) I just received my 890mm Apo Nikkor in the mail and noticed that in front of the aperture ring, there sits another ring with markings from 1 - 90. When I rotate it, sometime internal moves, but it isn't visible when looking through the lens...can anyone tell me what this might do?

10. ## Re: 890mm APO NIKKOR IMAGE CIRCLE @ 1:1 & INFINITY

Originally Posted by Craig Tuffin
Thanks for your help everyone but on another note (but still in regards to this lens) I just received my 890mm Apo Nikkor in the mail and noticed that in front of the aperture ring, there sits another ring with markings from 1 - 90. When I rotate it, sometime internal moves, but it isn't visible when looking through the lens...can anyone tell me what this might do?
Opens up a slot to insert all your process paraphernalia - stops, filters, e.t.c.

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