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

[Asher Kelman]

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.

I really appreciate the time Dan, you and others have taken to help set me on the right path. I have now one copy of a 760 mm Nikkor and a 471/2 inch Red Dot Artar, Scneider label. I will be getting alternates and sell what I don't need.

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.

Since Goerz apparently adjust the lens spacing either side of the aperture to optimize more for shooting at infinity than 1:1, although the performance are still stellar everywhere, could it be that these adjustments affect the image circle and circle of illumination, or is this going to be trivial?

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.

We know form Learoyds work at 1:1 with the Apo Germinar at 750 mm, thesystem covers the paper, albeit with degraded corners which we recognize but most folks expect for a classic portrait, where we'd want, (and put in), vignetting, anyway.


Asher

[Dan Fromm]

Kerry, what the OP wants to do needs around 8 lp/mm with usable contrast for much, not all, of the frame. How much depends on how he positions his subject.

There are at least two coverage concepts used on this forum. The generous one -- circle illuminated, and never mind about resolution or contrast off-axis -- is too vague to be safe to use. The more stringent one -- how far off-axis is the image usable? -- is used by at least Rodenstock and Schneider. I haven't found MTF curves, which address the question directly, for Schneider process lenses but Rodenstock published MTF curves for Apo-Ronars in their Process Lens Handbook.

Apo Ronar MTF curves, as published in the Process Lens Manual are surprising. As far as I know all Apo Ronars have the same prescription, but some focal lengths have nil contrast at 8 lp/mm, and with bad astigmatism; others have as much as 60% contrast at the edge of coverage with nil astigmatism. I"m not sure there's a pattern. This is very disturbing since it isn't consistent with what I think I know.

Some time ago Eric and I had a polite disagreement about Apo Saphirs. I found mine sharpest centrally at f/16, he insisted they as good wide open. He rechecked his calculations, concluded that I was right. Further on that point, his calculations show that they're essentially aberration free to around 15 degrees off axis; Boyer claims they cover around 48 degrees (less for the longer ones). Boyer are optimists, Eric may be too demanding, Schneider and Rodenstock seem to be realists.

We agree that the only way for the OP to find lenses that will meet his needs is to buy and try. One reason is a lack of clarity about what he needs and what published coverage figures (from users and from the manufacturers) mean. The other, which hasn't been discussed much, is variability in beat-up old lenses' quality. Some are in good order and perform as they did when new; others, e.g., that Wray I mentioned in this thread, aren't.

A 42 incher might do for the OP. A 750 Germinar does for Learoyd, who doesn't seem to frame tightly. But the OP would probably be safer with a 48 incher, and fortunately he has the space to use one.

Cheers,

Dan

[Asher Kelman]

Kerry, what the OP wants to do needs around 8 lp/mm with usable contrast for much, not all, of the frame. How much depends on how he positions his subject.

There are at least two coverage concepts used on this forum. The generous one -- circle illuminated, and never mind about resolution or contrast off-axis -- is too vague to be safe to use. The more stringent one -- how far off-axis is the image usable? -- is used by at least Rodenstock and Schneider. I haven't found MTF curves, which address the question directly, for Schneider process lenses but Rodenstock published MTF curves for Apo-Ronars in their Process Lens Handbook.

Thanks Dan (and once again Kerry in PMs), for your insight and generous help.

I'm strongly considering adding to a 760mm Apo Germinar to compare to the 760mm Nikkor. The later appears to be an asymmetrical design and might be different than the 760 Germinar which we know gives just adequate coverage in the reference work of Learoyd. We must look to do at least as good, but not worse! So the 760 Apo Germinar sounds necessary to test.

I'd test the Apo Saphirs if I found them! Someone here seems to be looking for me, LOL. When I ask, they say, we just had a call for the same lenses!

Obviously I'm not going to be scanning giant sheets of film to characterize the lenses, but I might put 4x5 film over key areas in the image circle on a vacuum board. I am getting more lenses than I will use as I'm sure that in practical use, there will be surprises and I am not prepared to invest a year with testing one lens after the other. Instead, I'll do everything in one go and get it over and done with!

Asher

[Dan Fromm]

Asher, according to my Apo Nikkor catalogs the 760 is a dialyte type. Symmetrical. There should be four strong and no weak reflections from each cell. If it is a tessar type there will be two strong and one weak reflection from the rear cell; the weak reflection may be hard to see.

Long Apo Saphirs are very uncommon. If you're up for paying 1982 list price (750, $2500; 800, $2800; 900, $4900; 1200, $8700) Rolyn Optics might have some new old stock lenses.

[Kerry L. Thalmann]

Kerry, what the OP wants to do needs around 8 lp/mm with usable contrast for much, not all, of the frame. How much depends on how he positions his subject.

Is the paper he's using to capture these images even capable of 8 lp/mm? I have no idea, so I'm asking. In general, the resolving capabilities of paper are much less than film. That is one of the reasons why I mentioned that his application is less demanding than the original application these lenses were designed for, and could, therefore, possibly push the coverage beyond the manufacturer's published specs. Of course, he has also stated he only needs maximum performance over the central 2/3 of the image area, which further relaxes the performance required for his application. Furthermore, such huge prints will have a much greater viewing distance than more modestly sized prints (or lith film designed for photographic reproduction), which reduces the required performance of the lens used to capture the image even further.

A 42 incher might do for the OP. A 750 Germinar does for Learoyd, who doesn't seem to frame tightly. But the OP would probably be safer with a 48 incher, and fortunately he has the space to use one.

The manufacturer's specs for the 42" Red Dot Artar list the coverage as 46 degrees with an image circle in excess of 180cm at 1:1. This is significantly more than the 168cm required by the OP for his application. Given the original intended application for this lens, one would hope the manufacturer's original specs were rather stringent and the performance criteria required higher for the intended application greater than those of the OP. So, why wouldn't a 42" Red Dot Artar meet the OP's needs (assuming it's in good condition and not suffering from damage or defects)?

Kerry

[Kerry L. Thalmann]

I'm strongly considering adding to a 760mm Apo Germinar to compare to the 760mm Nikkor. The later appears to be an asymmetrical design and might be different than the 760 Germinar which we know gives just adequate coverage in the reference work of Learoyd. We must look to do at least as good, but not worse! So the 760 Apo Germinar sounds necessary to test.

The basic design of these two lenses is different. As Dan stated, the 760mm f11 APO Nikkor is a 4/4 dialyte. I have both the manufacturer's brochure and one of these lenses. So, I can confirm that it is indeed a 4/4 dialyte. The manufacturer lists the coverage as 42 degrees for an image circle of 117cm at 1:1.

The 750mm f9 APO Germinar is not a 4/4 dialyte. The construction of this lens is a 6/6 symmetrical design. Again, I have both the manufacturer's brochure and a lens in my possession and can confirm this is correct. The manufacturer lists the coverage as 46 degrees at 1:1 for an image circle of 127cm.

It is interesting that Docter also published larger angles of coverage for these lenses for use at infinity (51 degrees at f9 and 56 degrees at f14.5) and that the coverage increased substantially when stopping down. You can read more about these specs in Arne Croell's excellent article on the Docter lenses. Note: this is a newer version of Arne's article and includes additional information not found in the article on the static pages of this site.

In any case, according to the manufacturer's specs on both lenses, the 6/6 APO Germinar should cover more than the 4/4 APO Nikkor. The 6/6 APO Germinar also seems to have more potential for extended coverage if the criteria of acceptable performance is relaxed.

But, once again, the only way to know for sure is to test both lenses side-by-side and determine which best suits your needs. At least in the case of the 750mm APO Germinar, you also have Learoyd's work as a reference to how this lens performs for this application.

Kerry

[Asher Kelman]

The basic design of these two lenses is different. As Dan stated, the 760mm f11 APO Nikkor is a 4/4 dialyte. I have both the manufacturer's brochure and one of these lenses. So, I can confirm that it is indeed a 4/4 dialyte. The manufacturer lists the coverage as 42 degrees for an image circle of 117cm at 1:1.

Kerry,

There sure is some muddle about this in the WWW!

(Jan 23, 2003; 04:09 p.m., photo.net)
Re: The debate about the symmetrical vs non-symmetrical designs of APO-Nikkors: There were two types made: Symmetrical (all f/9)240, 360,420,480,610 and(f/11)720; Asymmetric (all f/9)150,210,300,450,600,750,900,1200 and (f/14)1800. Modern (multicoated) versions were all symmetrical and all the symmetric ones had 4 elements in 4 groups. The asymmetric lenses 4 elements in 3 groups. Symmetric ones were based on artar & the asymmetric -tessar. All were optimised for 1:1 reproduction only. Angle of coverage goes from 35 degs to 46. Process Nikkors and W.A.Apo nikkors have >70 degs of coverage (info -from original Nikon literatures).

Source.

Well, my lens is a 760mm f11, so that does not fit into the symmetrical list which has a 720 mm f11 and neither does it match the asymmetrical 750mm f 9.0. I don't know where Vivek got his information. but clearly, it's not the entire story.

Asher

[Kerry L. Thalmann]

Kerry,

There sure is some muddle about this in the WWW!



Well, my lens is a 760mm f11, so that does not fit into the symmetrical list which has a 720 mm f11 and neither does it match the asymmetrical 750mm f 9.0. I don't know where Vivek got his information. but clearly, it's not the entire story.

Asher

Asher,

The 750mm f9 is a 4/3 APO Tessar type with less coverage (~35 degrees). The 760mm f11 is a 4/4 dialyte with 42 degrees of coverage. That's what mine is and what's listed in the Nikon brochure I have.

The list above is also incomplete. There were also 4/4 dialyte APO Nikkors in the 890mm f11 and 1210mm f12.5 focal lengths.

Kerry

[Dan Fromm]

Asher, I'm mortally offended that you don't believe me, the more so since I gave sources.

I have the catalog that Vivek Iyer quoted. It lists, among others, a 750/9 tessar type Apo-Nikkor. A newer catalog lists, among others, a 760/11 dialyte type Apo-Nikkor. Have your vision checked, you misread 750 for 760.

Kerry, I have a piece on Apo- and Process-Nikkors pending on the French LF site. I thought I gave Asher a pre-publication copy. It includes the lenses you listed. If you want a prepublication copy -- I think you have all of the catalogs that I do -- send me a PM with your e-mail address.

[Asher Kelman]

Asher, I'm mortally offended that you don't believe me, the more so since I gave sources.

Dont be offended, Dan, LOL, no mortal wound intended!!!!

I just couldn't locate the 760 f11 lens in the lists I have looked at, just the 720 f11 Vivek writes about. Maybe that's the mistake! Is there in existence a 72 f11 Apo Nikkor? Anyway, As Kerry points out, some sources so appear somewhat incomplete, so your new article is most welcome.

I have the catalog that Vivek Iyer quoted. It lists, among others, a 750/9 tessar type Apo-Nikkor. A newer catalog lists, among others, a 760/11 dialyte type Apo-Nikkor. Have your vision checked, you misread 750 for 760.

I totally believe you! Thanks!

Kerry, I have a piece on Apo- and Process-Nikkors pending on the French LF site. I thought I gave Asher a pre-publication copy.

I need to refresh my memory on that one. Could you send it to me at editor.opfATmac.com

Dan, this again pushes me to get the 750 Apo Germinar as well. The image circle should be greater too than my 760 f 11 Nikkor.

Asher