How do enlarger lenses differ from others?

[John D Gerndt]

Please forgive my ignorance here but why is it that each format requires its own enlarging lens? I have often used a longer lens than was specified to gain comfort/operational distance for small enlargements, that makes sense to me, but now I have discovered (after buying an expensive 12” lens) that my 210mm El Nikkor covers 8x10 nicely (at least at smaller,3x, enlargements).

Can anyone help me with the mechanics of enlarging lenses and if you want to add how they differ from copy lenses that would really delight my tiny mind.

Thanks!

[Bob Salomon]

The proper enlarging lens is equal to the diagonal of the format being printed - in other words the same focal length as a normal lens for the camera. If there is a problemg making the required print size due to a lack of enlarger column height then wide angle enlarging lenses are available for 35mm to 4x5". These allow 30% greater magnification at the same column height.

For very large printing up to 30 or 50x the negative size the G series of lenses are available. These are the only modern lenses where a slightly longre then normal lens size may be required. For instance for 35mm film for prints up to 50X the negative size a 50mm Rodadagon G is used. But for 6x6 cm a 105mm is used and an 80mm isn't made.

An enlarging lens is designed specifically to take a small original and make it up to very large. The enlarging lens usually has an illuminated aperture scale, a pre-set aperture scale and dis-engageable click stops - all of which make life simpler in the darkroom. In addition they hit optimal aperture 1 to 2 stops from wide open (quality lenses) and hold it for a couple of additional clicks on the aperture scale. They are normally designed to be used at stops larger then f22.

A process lens (probably what you call a copy lens) is designed to work at 1:1 not at very large magnification. In addition a process lens is corrected to only perform optimally at f22.It does not have an illuminated aperture, a pre-set aperture or disengageable click stops (unless it is in the last version of some Prontor Werke shutters).

If you want to make a 1:1 print a contact print would be better quality then using a lens. Providing you have a contact box with variable lighting to aid in burning and dodging.

[Michael S. Briggs]

There are several reasons that enlarging lenses are made in different focal lengths.

The extreme would be: let's make one lenses for all formats -- 300 mm for sub-35 mm to 8x10! But 300 mm enlarging lenses are big and expensive and require large distances from the film to the paper, so almost no customer who doesn't enlarge 8x10 would purchase this lens. So the manufacturers offer a range of focal lengths, suggesting for each film format the shortest focal length that they think delivers top quality results.

The longer focal lengths tend to have a slower maximum aperture. Some abberations increase with focal length, so the finest resolution on the film that can be resolved with a 300 mm lens is probably smaller than the finest resolution a 50 mm lens can resolve. This is acceptable because 8x10 is typically enlarged less than a 35 mm film. A print from an 8x10 film will still be sharper because the film was enlarged less.

Another reason is that it the lenses are optimized for different magnifications depending on the intended format. The 50 mm f2.8N El-Nikkor is optimized for 8X and suggested for 2X to 20X. In comparison, the 300 mm El-Nikkor is optimized for 2X and suggested for 1X to 4X. It would probably be less satisfactory then the 50 mm for an enlargement of 35 mm to an 8x10 print.

Each manufacturer offers their judgment of the shortest focal length enlarging lens that gives high quality for a particular format. Because of the optical designs used, this tends to be about the format diagonal. For example, Nikon lists the 240 mm El-Nikkor as their shortest enlarging lens suitable for 8X10. But this is a matter of judgment and the desired quality level, and also of the magnification used, so someone else might find the 210 mm lens satisfactory.

[Bob Salomon]

" the 240 mm El-Nikkor as their shortest enlarging lens suitable for 8X10. But this is a matter of judgment and the desired quality level, and also of the magnification used, so someone else might find the 210 mm lens satisfactory."

In some cases there is another, most important consideration.

Mount size and the lensboard size. 240mm lenses are usually a smaller mount then a 300mm. You can't use a lens that is larger then the board you want to use it on. A case in point is trying to put an 810 enlarging lens on a Beseler 45 with the 810 lamphouse.

[John D Gerndt]

Thanks Michael and Bob, you know your stuff. It is apparent from your postings that people who use a copy or process lens for enlargement are pushing the stone uphill, yet I have read that the Ronar CL is optimized for reproduction 1:3 to 3:1, not much different from the 300mm El Nikkor Michael mentioned though I’d guess that the Ronar is at f22 and not 11 or 16 as for the Nikkor.

I want to go the other way though. Ronars would be worse than full format diagonals (no?) You see, I do (I’m so ashamed) lack column height and would prefer to have that wide field lens. 30% off the 8x10 diagonal puts it to the Paragon 229mm, a lens of perhaps questionable heritage and I already have this El Nikkor 210. I don’t currently use a modern lens on my 8x10 so my corners are whacked anyway and I cannot get a grain magnifier into my corners to see if the 210mm is holding up.

I am wondering if and what I should start looking for to accompany any NEW and improved lens for my 8x10 camera. I am hoping I can spend all my money on that new and improved (modern)taking lens. I am hoping that, in the 3x range, I can stay with that 210mm and am wondering if there is good reason (Show me the physics boys!”) to hope.

Thanks for your expertise,

[Øyvind Dahle]

Make sure lens, the negative and the paperholder is parallel:

To know when they are parallel, use a flashlight and two mirrors, one with a hole in it to see the reflecting mirrors, the flashlight in between, or a expensive laser tool.

Then check if your lens is centered by scraping a x in the center of a negative and one x in each corner of your negative, and enlarging it, the x-es should be equally sharp. Or just a big x, the lines should be sharp all the way.

If your pictures look good, change nothing.

Øyvind:D