90mm for 6x17

[Ole Tjugen]

The fall off is after 70% of the circle so a lens with a larger circle will exhibt less fall off on the same format as a lens with a smaller circle.

No, not if the two lenses have the same focal length. What you are saying is that a 600mm Nikkor T-ED will have virtually identical falloff to a 120mm Nikkor SW, since both have about the same image circle (310 vs 312mm). That is demonstrably false.

Comparing two directly comparable modern lenses - Schneider Super Angulon classic and Super Angulon XL, both 90mm focal length, shows that it isn't even correct for THOSE lenses, from the same manufacturer.

https://www.schneideroptics.com/pdfs...xl_56_90_1.pdf

http://www.schneiderkreuznach.com/fo...R44907_1AE.PDF

Neither does the fall-off start at 70% of the image circle, nor does the one with the larger image circle show less fall-off at a given distance from the center - neither expressed as a measured distance in mm, nor in % of the total image circle.

So again, I would dearly like to see some documentation on the effect you describe.

[Bob Salomon]

No, not if the two lenses have the same focal length. What you are saying is that a 600mm Nikkor T-ED will have virtually identical falloff to a 120mm Nikkor SW, since both have about the same image circle (310 vs 312mm). That is demonstrably false.

Comparing two directly comparable modern lenses - Schneider Super Angulon classic and Super Angulon XL, both 90mm focal length, shows that it isn't even correct for THOSE lenses, from the same manufacturer.

https://www.schneideroptics.com/pdfs...xl_56_90_1.pdf

http://www.schneiderkreuznach.com/fo...R44907_1AE.PDF

Neither does the fall-off start at 70% of the image circle, nor does the one with the larger image circle show less fall-off at a given distance from the center - neither expressed as a measured distance in mm, nor in % of the total image circle.

So again, I would dearly like to see some documentation on the effect you describe.

No I'm not. I am saying that a 90mm 4.5 will start the fall off further out from the center then a 90mm 6.8 from the same manufacturer. Same for a 90mm 5.6 vs the f8. The SA and the SA XL are different designs. Try the 90mm 5.6 vs the 90mm f8 SA and leave out variations like the XL.

[Ole Tjugen]

Bob - the SA f:8 is 6 elements in 4 groups, the SA f:5.6 is 8 elements in 6 groups. So you might just as well say that THOSE are different designs?
Note that all three - f:8, f:6.8 and f:5.6 XL take exactly the same strength center filter, only the diameter is different due to the different size of the front element.

http://www.schneiderkreuznach.com/ar...an_su_1995.pdf


You can't make a general statement like that and then say that it doesn't apply to lenses of different design - how could the angle of coverage be different if the design were identical?

I don't have the relative illumination data for the F:8 or the f:5.6 non-XL, but the ones I do have contradict your statement.

[Bob Salomon]

Bob - the SA f:8 is 6 elements in 4 groups, the SA f:5.6 is 8 elements in 6 groups. So you might just as well say that THOSE are different designs?
Note that all three - f:8, f:6.8 and f:5.6 XL take exactly the same strength center filter, only the diameter is different due to the different size of the front element.

http://www.schneiderkreuznach.com/ar...an_su_1995.pdf


You can't make a general statement like that and then say that it doesn't apply to lenses of different design - how could the angle of coverage be different if the design were identical?

I don't have the relative illumination data for the F:8 or the f:5.6 non-XL, but the ones I do have contradict your statement.

Then go to the Linos site and download the Grandagon-N curves.

[Ole Tjugen]

Then go to the Linos site and download the Grandagon-N curves.

Which show that both the f:4.5 and the f:6.8 version of the Grandagon-N reach 1 stop fall-off at about 67mm from the lens axis. These too are of "different construction", did you notice? The f:6.8 is six elements/four groups, the f:4.5 is eight elements/four groups. Both give slightly less than cos^4 fall-off, but slightly more than the Schneider Super-Angulon f:6.8 "Classic". Even comparing a 6in4 to another very similar one from a different manufacturer shows that the rule doesn't hold...

[engl]

There is no such thing as falloff beginning at 70% of the field, it begins as soon a you go off the center axis. How rapidly it falls off depends on the design of the lens, and not how big the image circle is. This is easily checked in lens data sheets, as Ole points out.

A Super Symmar XL 80mm has greater falloff in the corners of a 4x5 frame (no movements) than a Grandagon-N 75mm, even if the Super Symmar has a slightly longer focal length and a much bigger image circle. Using image circle to estimate falloff is misleading.

[richard brown]

Back to the original poster.... so glad to hear you bought the nikon f8 90mm.... i have a couple of 617 cameras and the fuji 90 had the optical characteristics of toilet paper out at the edges and some fall off. the older super angulon 90 f8 wasn't much better. But the nikon is great. I know nothing of the scientific stuff, just the negatives and what they can resolve and how the print looks which is ultimately, what I hope is our goal.
Happy shooting with your new glass!!!