Which 360mm lens has the largest image circle

[Vaughn]

Computar Symmetrigon lenses...wonderful lenses, but certainly Drew is correct -- their coverage was average for the focal length. Sharp and good contrast, especially using the supplied lens hood.

[Oren Grad]

Oren, there were all kinds of things made under Computar label, and I get the impression that lots of the coverage complaints are either due to Computar Symmetrigon lenses being mistaken for their graphic ones, or else due to mechanical vignetting issues in smaller shutters, or perhaps an economy line of lenses.

Nothing to do with the Symmetrigons nor with the shutters. The issue is specifically f/9 process lenses labeled Graphic Kowa that look cosmetically identical to the f/9 Computars but are different optically and have smaller coverage. Again, the details are teased out over the course of the discussion in the thread I linked.

[Lachlan 717]

I have a barrel 240mm Graphic Kowa that I can’t edge out at full movements on 7x17…

Trouble is, it’s fixed in the barrel. No way to Copal shutter mount it without significant machining.

[ridax]

I've always wondered if the extra coverage of the old f/7.7 14 inch Dagors in terms of optical design is really any better than the final Kern versions, or simply due to their bigger shutters and less mechanical vignetting. A tradeoff.

I don't have the particular f/7.7 14" American Dagor version but as I said above, I am sure the total illuminated field in Dagors depends on the glass elements size but the sharp covered field depends on the cell spacing only. My 360mm f/7.7 German Dagor from the 1920s is really an f/7.7 but my 19th century f/7.7 480mm pre-Dagor is actually a f/6.8 lens with the aperture mechanically stopped at f/7.7. That 480mm has considerably larger glass elements (https://www.largeformatphotography.i...=1#post1655316).

But sharp-covered field is another story. The lower left graphs here http://dioptrique.info/OBJECTIFS7/00334/00334(.GIF are for the astigmatism and field curvature. In f/6.8~f/7.7 Dagors, astigmatism gets visible enough at about 40° (20° on the scale as the scale shows half of the field), then disappears and then gets really prominent again beyond about 60° (30° to each side of the center). Put the lens cells at a slightly larger distance from each other, and the mid-field astigmatism at 40° gets smaller, and the 60°+ astigmatism gets bigger - as in the later Dagors that are sharper in the mid field but have their total sharp-covered field smaller.

I have compared older Dagors and pre-Dagors to the Hugo Meyer Görlitz Doppel-Anastigmat Dagor copies in 210 to 240mm and in 300mm focal lengths and to a later Goerz American 210mm Kenro K Dagor. The Meyer copies had the largest sharp-covered field but had to be stopped to f/32 instead of the original Dagors' f/22 to get the same mid-field sharpness. The Kenro was the sharpest mid-field and had the worst sharpness at the very edges. And moving any of the lens cells out approximately one full turn of the threads, made the Meyers' sharpness distribution exactly equal to the older Dagors' one, and one more turn made them all equal to the Kenro.

The change in the astigmatism correction over the years was not only due to the fact that enlargements became more important than in the 19th century but more due to the emergency of panchromatic and especially of the color films. Please note the difference of the Dagor's astigmatism for the red and for the blue rays in graphs linked above. In red, it is nearly twice worse at 40° and a lot better at 60°+. So they had to change the cell spacing just to make the later Dagors perform the same in the full spectrum as the original Dagors performed with blue-sensitive emulsions.

[ridax]

But with all that spacing manipulations - personally, I still would not go beyond 80° with f/6.8~f/7.7 Dagors as the mid-field sharpness is also important for me, and it decreases quite rapidly with the attempts to get a larger coverage. I still don't know how close can I get to the f/9 Dagor's declared 100° if I put its cells closer.

I also would consider buying a proper Computar if its edge performance were anywhere near to a f/9 Dagor's, and I would appreciate any proof of that.

[Corran]

Image circle about 800mm would be 20"x24" image format?

The 450mm f9 Nikkor M is a Tessar formula with about 52 degrees of image cone, at f22 it has an image circle of 440mm at f22... not even close to ~800mm and no, stopping down lots will not increase the image circle to any where near 800mm.

Attachment 231819


For a 360mm focal lenght lens to make about 800mm image circle requires about 95 degrees if image circle cone or a "Biogon" or "wide field gasuss" lens design/formula or similar.. fact and reality IS, not gonna happen or it will be one of those rare single off lenses or have a lens designed specific to this need.

The other importaint bits of info, what exposure aperture, what are the image goal expectations, what about the shutter and all...?

Easier alternative would be to use a ..... pin hole.


Bernice

OP, you will get wildly different information, often from "experts" who cite manufacturer specs, other times from those who have actually used the lenses in question. Always test your own. Some may view image quality differently...I see one person citing poor performance on images I see extremely good performance from.

From my personal experience, the Schneider 360mm Symmar (non-S) covers 12x20 with a good amount of movements (rise/fall). I have not hit hard edge vignetting with it on my Wisner. The 450mm Nikkor-M is the same and many reports of even larger formats exists from users. The Nikkor is the most useful general-purpose ULF lens, hence their continuous upwards price movement.

Computars and Graphic Kowas are also excellent performers but research heavily. Best purchased from an experienced user or with a generous return policy. I'm not selling mine .

[Tin Can]

I am not an EXPERT

However I can read

NIKON Brochure attached link below shows a NIKKOR 360 f6.5 has significantly more coverage than the 450 f9 Page 15

I bought one and not the 450 by reading actual published data

https://www.mr-alvandi.com/downloads...mat-lenses.pdf

[ridax]

I see one person citing poor performance on images I see extremely good performance from.

I see at least two. :)

But we don't need to have identical opinions on any facts. What we need is to understand each other. That's why I like to cite aberrational curves: those represent facts, those are understandable with some experience, and they may be interpreted to be great to acceptable to inappropriate by each person for each particular task.

Detailed images like those posted in that older thread are also a great source of information to make one's own decisions on. Myself, I really would get the Graphic Kowa if those images looked differently. Others like them as they are. And that's perfectly OK.

[ridax]

Well yes I should admit it's hard to evaluate a lens itself at f/64, with the diffraction limit that severe and with no means to detect which of the subject parts were actually in focus. May be I liked the lens if I saw something shot at f/32....

[Bernice Loui]

When does a "lens" become a pin hole non-lens?

Given the example of 450mm f9 Nikkor M stops down to f128... what is the actual image circle at f9 -vs- f128? This question applies to any lens with an adjutiable aperature that goes past f64.. and goes back to reply# 18 asking the OP and others about exposure aperture. This essentially fixes the optical requirements of this question.. Ponder what an optical device would be like to deliver 100 degrees of image cone to over 800mm at it's focal plane and exposure aperture of f1.0... or using a pin hole with an effective exposure aperture of f256 or smaller_?_

Oh, 12"x20" requires a image circle about 588mm (wil that 450mm f9 Nikkor M fully cover 12"x20" at f9..stopping down the lens aperture is not allowed), which is smaller than 20"x24" or what this "discussion" was about based on the OP's inquiry.

This presentation on pin hole or lenless image making and lenses used to make images is a worthy read and study. Does a nice explanation of how this stuff works.
http://graphics.cs.cmu.edu/courses/1...s/lecture3.pdf

One recent example of wide angle pin hole image making for digital cameras..
https://thingyfy.com/blogs/news/the-...s-in-the-world

Typically, ULF images are contact printed, not projection enlarged. This bends the optical needs lots as 5 lpm is enough resolution for a contact print or exposure apertures of f90 and smaller can be absolutely good enough. If the same f90 plus mind set/value system film image is projection magnified-enlarged about 100x, would the image results be acceptable?

~Much a matter, opinion and more about image making goals, no?

Back to the quesstion of lenses with 800+ mm diameter of image circle.. Schneider introduced their XXL "fine art" series of lenses in the late 1990's as their answer to the lens question from the ULF folks. This was about the time when there was growing interest in ULF up to 20"x24"...

Schneider made a 550mm (dagor), 1100mm (artar) and later a 770mm. All three in Copal# 3 shutter, all three had a spec image circle of 900mm @f22 (yes, still a lens at f22, not a pin hole).
http://linhof.com/wp-content/uploads...rt-CS-engl.pdf


Bernice

Well yes I should admit it's hard to evaluate a lens itself at f/64, with the diffraction limit that severe and with no means to detect which of the subject parts were actually in focus. May be I liked the lens if I saw something shot at f/32....