The quality and technical differences in Process lenses at 600mm and longer?

[Asher Kelman]

Process lenses are notable for generous coverage and relatively low cost for their quality.

We know the Goerz and Docter lines slightly altered the optimal 1:1 spacing of the lenses, so their variants could perform equally or better at infinity instead of 1:! for copying.

I'm interested in 1:1 work and having the maximal image circle. Detail to the edges are not so critical. So how do Wray, Nikon and Boyer lenses compare to the Red Dot Artars in these respects? I can find interesting info on the Boyer lenses but no comparisons. Do the asymmetrical Nikon Process lenses have larger angles of projection?

Dan From has kindly helped me with great links to background, but I'd also like any user experience or user examples to learn more.

Thanks,

Asher

[Dan Fromm]

Where did you get the idea that process lenses have generous coverage? And remember, the longer the lens the narrower the angle covered. This because all aberrations scale with focal length and some with angle off axis.

Detail to the edges are not so critical

.

Don't be coy. How much coverage do you need? And what focal length(s) do you need? The more forthcoming you are about what you want to accomplish, the better the advice you'll get.

Remember that the last time you started this discussion you were told very consistently that your goals couldn't all be met at the same time. If your goals haven't changed, the news you get won't change either.

[Asher Kelman]

Where did you get the idea that process lenses have generous coverage? And remember, the longer the lens the narrower the angle covered. This because all aberrations scale with focal length and some with angle off axis.

.

Don't be coy. How much coverage do you need? And what focal length(s) do you need? The more forthcoming you are about what you want to accomplish, the better the advice you'll get.

Remember that the last time you started this discussion you were told very consistently that your goals couldn't all be met at the same time. If your goals haven't changed, the news you get won't change either.

Hi Dan,

I'm imaging using two 15 ft rooms separated by a wall, (which could, if need be be moved). The first lens I have bought is a 760 mm Nikkor. I chose this as a start since Learoyd used a similar focal length Germinar to image 40"x72" in his recent show at the Gallery in San Francisco. I am seriously considering a 47.5" or else 48 inch Georz or Red Dot Artar, but any special insight would be helpful. A Saphir is not currently available but a few Wray lenses are. So any experience with the Wray lens would be great, as I cannot find detailed reports in the longer focal lengths, like 48 or 68" or so. The projected image, at 1:1 magnification, will be generally be directed to Ilfochrome paper, 40" by 84", with the actual image being up to 36" by 72" or less.

The imaging standard is that of Learoyd's work, meaning that I can tolerate drop off of detail at the periphery as long as the central 2/43 of the actual image is sharp and evenly illuninated.

Have I missed anything? Let me know if there are any remaining points to define or clarify.

Thanks again for your help,

Asher

[Dan Fromm]

Ok, so your greatest film-to-subject distance is a little under 30 feet. Since at 1:1 film-to-subject distance is 4f plus a little for the internodal distance, the longest lens you can use is around 80 inches. Good luck finding something that long.

At 1:1 the 1200/12.5 Apo-Nikkor covers 175 cm, the 1780/14 covers 231 cm.

The 1200/12.5 Apo-Saphir covers 168 cm at 1:1.

The 1800/16 Apo-Ronar covers 250 cm at 1:1. The 1200ers cover 168 cm.

The dimensions you give -- 3' x 6' -- require a lens that covers 170 cm. A four foot lens -- Apo-Artars seem to be the most common -- will just do what you need.

You'll need a lens that delivers usable contrast at 8 lp/mm, might be able to shoot at apertures as small as f/128 effective, f/64 set.

Happy hunting!

[Asher Kelman]

Thanks, Dan!

Well then, there's a good response!. Any comments from you on the Apo Wrays? I've been offered a NOS 48" and a 68". But there's a 70" RDA that is in the sidelines as well.

Asher

[Dan Fromm]

Buy them, try them, and if you don't like them resell them.

I have one Apo Process Lustrar Ser. II, a 14 incher. The VM says that the Ser. IIs are the best of that line. Mine is awful, just awful, but it is filthy inside and I tried it without dismantling and cleaning.

RDAs are known quantities, but as usual with used lenses condition matters a lot.

[Asher Kelman]

Buy them, try them, and if you don't like them resell them.

I have one Apo Process Lustrar Ser. II, a 14 incher. The VM says that the Ser. IIs are the best of that line. Mine is awful, just awful, but it is filthy inside and I tried it without dismantling and cleaning.

RDAs are known quantities, but as usual with used lenses condition matters a lot.

Dan,

I read that they can get "cloudy" as they age. Is yours filthy from dirt, do you think, or could it be this aging process. Is it yellow too? I wonder if it has any rare earths that yellow and can be clarified by exposure to sunlight?

Asher

[Dan Fromm]

It looks like typical old lens schmutz, Asher. Probably sublimed lubricants, should come off. But taking the thing apart isn't easy, lotsa fiddly little setscrews have to come out before the cells can be extracted from the barrel. I have a perfectly fine 360/10 Apo Saphir so don't see the point of bothering with the Apo Lustrar.

OTOH, I have a couple of 135/4.8 Lustrars that have major crud that won't come off on the surfaces that face the diaphragm. Not sure what made it. The lenses came in SynchroCompur P shutters on Peckham Wray helicals. One of the shutters could be rescued and the helicals made two friends happy. The price, including delivery, was very right so I'm pleased with the deal.

[Asher Kelman]

It looks like typical old lens schmutz, Asher. Probably sublimed lubricants, should come off. But taking the thing apart isn't easy, lotsa fiddly little setscrews have to come out before the cells can be extracted from the barrel. I have a perfectly fine 360/10 Apo Saphir so don't see the point of bothering with the Apo Lustrar.

OTOH, I have a couple of 135/4.8 Lustrars that have major crud that won't come off on the surfaces that face the diaphragm. Not sure what made it. The lenses came in SynchroCompur P shutters on Peckham Wray helicals. One of the shutters could be rescued and the helicals made two friends happy. The price, including delivery, was very right so I'm pleased with the deal.

Dan,

I also heard that some of these lenses get "coated" from airborne vapors where darkroom chemicals are not well ventilated and this perhaps is more readily removed on the outside surfaces.

Your advice to buy and try is probably the best.

Asher

[Kerry L. Thalmann]

Ok, so your greatest film-to-subject distance is a little under 30 feet. Since at 1:1 film-to-subject distance is 4f plus a little for the internodal distance, the longest lens you can use is around 80 inches. Good luck finding something that long.

At 1:1 the 1200/12.5 Apo-Nikkor covers 175 cm, the 1780/14 covers 231 cm.

The 1200/12.5 Apo-Saphir covers 168 cm at 1:1.

The 1800/16 Apo-Ronar covers 250 cm at 1:1. The 1200ers cover 168 cm.

The dimensions you give -- 3' x 6' -- require a lens that covers 170 cm. A four foot lens -- Apo-Artars seem to be the most common -- will just do what you need.

You'll need a lens that delivers usable contrast at 8 lp/mm, might be able to shoot at apertures as small as f/128 effective, f/64 set.

Happy hunting!

Dan,

The numbers you provided seem to be based on the manufacturer's stated coverages for these lenses. At least, they closely agree with the data sheets I have for the APO Ronars, APO Nikkors and Red Dot Artars.

For example, a Rodenstock publication datet June, 1974 titled "Hints and Tables for Work with Rodenstock APO-Ronar Lenses" list the coverage angle as 40 degrees and the image circle as 175cm at f22 for the 1200mm APO Ronar for a 1:1 magnification ratio.

A Goerz brochure titled "The Lens for the Graphic Arts - Goerz Red Dot Artar" lists the coverage as 46 degrees for all focal lengths (from 4" to 70"). There is also a table that lists the film formats covered at various magnification ratios. For the longer focal lengths, the listed formats at 1:1 are:

30" (762mm) - 30"x40" (127cm format diagonal, 129cm IC at 1:1 and 46 degrees)
35" (889mm) - 36"x45" (146cm format diagonal, 151cm IC at 1:1 and 46 degrees)
42" (1067mm) - 48"x56" (187cm format diagonal, 181cm IC at 1:1 and 46 degrees)
47.5" (1207mm) - 48"x64" (203cm format diagonal, 205cm IC at 1:1 and 46 degrees)
70" (1778mm) - 72"x80" (273cm format diagonal, 302cm IC at 1:1 and 46 degrees)

The last two sets of numbers in parentheses are the calculated format diagonal and image circles at 1:1 based on the stated 46 degrees of coverage.

It is obvious from the numbers above, that any Red Dot Artar 42" or longer will cover the required 36"x72" image size at 1:1.

What is less obvious is how the shorter focal lengths will do. Keep in mind, the original application for these lenses was very demanding in terms of image quality. Most of these process lenses throw larger image circles than their stated coverage angles. In other words, they don't employ field stops, or other means of mechanical vignetting to limit their coverage to the stated angle (40 degrees, 46 degrees, etc.). So, the image quality degrades beyond the stated coverage, but there is still image there.

The question then becomes what level of image quality is necessary for the OP's application? He's imaging directly on paper, and not on high contrast lithography film. He also stated that he doesn't mind degraded image quality beyond the central 2/3 of the image area. With that in mind, I suspect a 35" Red Dot Artar will probably meet his needs. As may some of the 30"/750mm lenses, like the 30" Red Dot Artar and 750mm APO Germinar.

Since this is subjective, as you recommended, testing the individual lenses is really the only way to determine if anything shorter than a 42" Red Dot Artar will meet the OP's requirements and desired level of image quality for his unique application.

Kerry