Enlarger lens or Macro Prime lens for DSLR Scanning?

I've been debating between adapting an enlarger lens like a rodenstock apo or using a clinically sharp zeiss macro prime.

Relatively speaking, what would yield sharper results for 35mm DSLR scanning?

 

Thanks.

I'd think enlarger lenses are not optimized for the distances involved, though they work great for the ratios they are designed for.

A good example of either one will probably out resolve the film images in any case. When I was building a set up for this I experimented with both an El Nikkor 80 mm f/5.6 and a Pentax 50 mm f/2.8 DFA macro. The Pentax macro is noticeably better for scanning, even though the 80 mm always made excellent prints.

I've been debating between adapting an enlarger lens like a rodenstock apo or using a clinically sharp zeiss macro prime.

Relatively speaking, what would yield sharper results for 35mm DSLR scanning?

 

Thanks.

I've tried both, and IME there's no perceptible difference between using a good-quality enlarging lens - Componon-S, Rodagon, Neonon, El-Nikkor, etc. - and a macro lens. The enlarging lens might get you a slightly flatter field and less vignetting, depending on which macro lens you compare it to.

 

OTOH, an enlarging lens will need a bellows or tubes+adapter arrangement; making the rig a bit more complicated.

 

And if your setup is makeshift, like hanging a tripod over a light box, all bets are off and the lens is really the least issue you'll have to contend with!

 

You'll need to use an aperture of f/6.3 to f/8 anyway, in order to cover film curvature. At that sort of aperture you'll be hard-pressed to see IQ differences between top-quality lenses, as the effect of diffraction will already have kicked in.

Edited August 25, 2021 by rodeo_joe|1

an enlarging lens will need a bellows or tubes+adapter arrangement; making the rig a bit more complicated

 

Yes, but also more flexible. I think the flatter field tips the balance.

A real copy stand or such-like device is nearly necessary if you're doing much copying

 

I prefer my Nikon Super Coolscan 9000, but find this a great alternative when I'm doing only a few images:

 

Honeywell Universal Repronar

note that this has bellows and an enlarger lens. can be hooked up to most cameras.

Edited August 25, 2021 by JDMvW

I'd think enlarger lenses are not optimized for the distances involved

 

I don't follow. Surely the close distances favor the use of enlarging lenses.?

The better enlarging lenses are optimized for making large prints, not operating at near 1:1 like most slide/neg copying operations. Now, I may have misunderstood the OP, but I read it as 35mm slide/neg copy work, not some arbitrary subject being copied by a 35mm format dSLR sensor. Devil is in the details!

Most expert commentary I have seen involving enlarging lenses favors reversing the lens for 1:1 use.

In a setup similar to the one shown below, I don't think it matters much, although I would probably choose the macro lens as it is more versatile.

Hey, that's my slide copy setup! With a DX camera I found an 80mm enlarging lens worked well. With FX, I think I switched to the 55 Micro, but not sure anymore. At 1:1 it shouldn't matter which way round the lens is because the ray angles are the same. Armchair speculation- the best lenses for 1:1 are probably symmetric, maybe even a couple off-the-shelf achromats mounted back to back.

A better edit of above (I am a terrible speller!

 

Optically, I don’t think a good enlarger lens will produces a sharper image than a prime macro. Both are optimized to image a flat-to-flat. In other words, enlarger lenses are optimized to image a flat film and project it’s image on a flat light sensitive surface. Conversely, a macro is also optimized to image flat-to-flat.

That being said, a macro has advantages. A macro that properly attaches to a camera will be electronically and mechanically coupled. Thus, the macro benefits as it is granted the benefits of the camera’s automation.

 

When doing close-up work with lenses other than a macro, you will grapple with what we call “bellows factor”. Allow me to explain: The f-numbers engraved on the lens barrel are valid when the lens is focused at infinity. Infinity, Latin for “as far as the eye can see” will be a distance about 3000 focal lengths ahead of the lens. Light rays from objects that far forward of the lens arrive at the lens as bundles of parallel waves. The lens changes the direction of travel of arriving light waves. Their revised path will be converting rays that meet up at some distance downstream from the lens. A measurement of this distance is what we label as “focal length”. Since the lens as limited ability to refract (Latin “to bend backwards”) light rays from objects closer than infinity must travel further to make the convergences. We label this elongated travel distance “back-focus”.

 

OK – how does “back-focus” effect explore as apposed to “focal length”? Suppose a 50mm lens is mounted an set to f/11. Since the f-number is the focal length divided by the aperture diameter, its diameter will be 4.55mm. The f-number tells us how this lash-up compares with other lenses as to light transmission. In other words, any lens set to f/11 grants the same exposing energy as another lens set to f/11.

 

However, the f-number as engraved on the lens barrel is only valid when the lens is imaging an object at infinity. When doing close-up work, the object will be placed extremely close to the lens thus the back-focus will be extremely elongated. At magnification 1 (unity or life-size), the back focus distance is two focal lengths. A 50mm lens imaging at unity, the object will be 100mm forward of the lens and the focused image will be 100mm downstream from the lens. The distance focus plane to object is 200mm and the focal length is ¼ of this distance.

 

Translated—The f-number for this 50mm lens is now computed as 100 ÷ 4.55 = 22 (written f/22. Thus, the engraved f-number is wrong and this error is called “bellows factor”.

 

Macro to the rescue – The macro lens has a trick up its sleeve. The forward lens group of the macro is a powerful magnifier. The diameter of the iris (aperture), as seen peering into the lens from the front appears larger than life. This enlarged view functionally allows more light to traverse the lens when working in close. In other words, the macro self-corrects for bellows factor.

 

Is this important? If a enlarger lens is used, no automation and no auto correction for bellows factor, Likely under-exposure results.

Most expert commentary I have seen involving enlarging lenses favors reversing the lens for 1:1 use.

At 1:1 you have totally symmetrical conjugate focii, therefore reversing the lens makes absolutely no difference. It's only when you get (well) beyond life-size that reversing the lens is advantageous. Besides, the datasheets for most enlarging lenses distinctly say that the optimum range includes 1:1 - usually a range of 1x to 10x enlargement.

The forward lens group of the macro is a powerful magnifier. The diameter of the iris (aperture), as seen peering into the lens from the front appears larger than life. This enlarged view functionally allows more light to traverse the lens when working in close. In other words, the macro self-corrects for bellows factor.

Errr, no it doesn't. Some macro lenses shorten their focal length slightly with closer focus, but most still have an effective aperture that's way smaller than the marked aperture at 1:1. In fact the better auto macro lenses report their true working aperture to the camera. I.e, f/11 or f/13, when the aperture set is f/8.

Likely under-exposure results.

Like TTL exposure metering hasn't been common for 50 years or more?