1800mm and Beyond

[Hermes07]

Would really like some opinions on this.

I've always wanted to experiment with long lenses, REALLY long. I have plenty of bellows but 70" is, as far as I know, the longest focal length manufactured commercially. The only lenses I can find longer than this are achromats designed for use as telescope objectives e.g. - http://www.intane-optics.com/product...catalog-1.html

Would these be any use whatsoever as taking lenses (for colour or orthochromatic processes?)

Does anyone have any experience as to the sharpness of these lenses wide open or stopped down? Any notion of the sort of useful coverage they'd give for positives that will be directly viewed or contact printed?

Sorry for asking such vague questions - hopefully someone who has once tried a lens of this type for large or ultra-large format photography will be able to chime in and educate me a little.

[Dan Fromm]

Boyer made a handful of 2500/12.5 Apo Saphirs. Most of them were bought by the French Atomic Energy Commission.

I have an Apo-Saphir catalog with a copy of a letter dated October 27, 1965 from the director of the Central Arms Laboratory in which he states that the lab has just received 53 Apo Saphirs, focal lengths 300, 450, 600, 900, 1200 and 2500 mm. He says that they fully met specifications, in particular in respect to resolution, air- and water-tightness, and corrosion resistance. I believe these lenses were used to photograph A-tests.

There's a picture of 14 2500/12.5 Apo-Saphirs in the catalog. The catalog was issued while Andre Levy owned Boyer. Eric Beltrando tells me that he saw a batch of 8 2500/12.5s at CEDIS-Boyer some years after control of the firm passed to CEDIS. AFAIK most of the Apo-Saphirs that went to Mururoa are still there.

These are 30 degree lenses, cover 1340 mm.

USAF bought 96"/8 and 144"/8 lenses from Perkin Elmer. I think you have as good a chance of finding one of them as of finding a 2500 Apo-Saphir.

You might want to look at the 1963 GOI lens catalog. It lists Soviet lenses known to the State Optical Institute up to that date and includes some monstrous lenses for aerial cameras. You can download it from http://www.lallement.com/pictures/files.htm More unobtanium, I'm afraid.

[Hermes07]

Thanks for the information Dan.

I had read a little about about the 2500mm Apo Saphir (I believe in an article you authored) - but never thought I had much chance of actually finding one for sale.

Fear the same might be said for the soviet lenses.

My Russian is rusty and my French is even worse - I'll will try both avenues on the chance that they will turn up a lens of this size but I'm not holding my breath. I seem to recall reading that there was only 1 of each made of the Perkin Elmers you mentioned so they're pretty-much out of the picture if that's the case.

The rarity of these lenses is what's driven me to consider the achromats. The trouble is that I have no idea how they'd perform as taking lenses. If it came to it I could try using two of the large achromats with a negative element in between to improve the quality in a cooke triplet kind of design, but if it's going to produce completely unusable results I'd much rather not spend a grand attempting it.

[Dan Fromm]

You're pretty much in refracting telescope territory, might want to look for places where users discuss them.

You might also find this http://alag3.mfa.kfki.hu/astro/giantlenses/200mm.htm site interesting. All sorts of odd stuff there, including leads to manufacturers.

[johnielvis]

I posted before about rolyn optics...


they have these lenses nos

not cheap likely, but new

rolyn.com

[Photomagica]

Have a looks at Surplus Shed as well for Achromats.
http://www.surplusshed.com/pages/cat...elenses_3.html

Achromats are very sharp on axis - typically diffraction limited. They deteriorate rapidly off-axis but might perform very well if your film isn't too large.

Bill Peters
Photomagica

[Hermes07]

Thanks for the links but I've tried all those sites in the past. Rolyn do not have any of the 2500mm Apo Saphir despite what their site says.

Have found plenty of sources for the achromats. Trouble is, all the reviews/discussions are about using them in telescopes with eyepieces which is very different from using them to cover a large sheet of film or paper. Ideally Id want a 2400mm lens with 25 degrees of coverage and a 4000-5000mm lens with 12 degrees of coverage. Anyone have any idea what I'd get if I tried to use an achromat to get those sorts of numbers, Usable? Usable if stopped down a lot? or complete waste of time?

[GPS]

...
Have found plenty of sources for the achromats. Trouble is, all the reviews/discussions are about using them in telescopes with eyepieces which is very different from using them to cover a large sheet of film or paper. Ideally Id want a 2400mm lens with 25 degrees of coverage and a 4000-5000mm lens with 12 degrees of coverage. Anyone have any idea what I'd get if I tried to use an achromat to get those sorts of numbers, Usable? Usable if stopped down a lot? or complete waste of time?

Hermes, do yourself a favour and come to your senses. The achromats you talk about are lenses that focus an image to an eyepiece. How on Earth could they cover a LF film (much more then ULF you speak about in your first post)? The film is even bigger than the diameter of the lens!

[Hermes07]

Are you suggesting that one of these lenses will only illuminate an image circle of a few centimeters/inches? That's contrary to my basic experience with other small achromats which have all illuminated big circles.

If you're suggesting that they will illuminate but be totally unusable outside the dead centre of the image circle then please, share your experiences in more detail. Will they still be unusable at f/32?, at f/128? What angle can they cover sharply before their performance drops off?

[E. von Hoegh]

Are you suggesting that one of these lenses will only illuminate an image circle of a few centimeters/inches? That's contrary to my basic experience with other small achromats which have all illuminated big circles.

If you're suggesting that they will illuminate but be totally unusable outside the dead centre of the image circle then please, share your experiences in more detail. Will they still be unusable at f/32?, at f/128? What angle can they cover sharply before their performance drops off?

They will illuminate quite a large circle, but their sharp coverage is limited to a few degrees - by a few I mean 3 to 4, if that. You could check out the telescope oriented site mentioned above, they will have the coverage info you want. You should calculate the angle of sharp coverage you need from each focal length and work from there. I don't think you mentioned what format you will use. If 35mm, those telescope achromats might be surprisingly good if well baffled. But keep in mind that they are designed to focus an image on an eyepiece (as mentioned above) with a diameter of what, an inch??

Edit: You know a pair of achromats with a central stop make a rapid rectilinear type lens, right?