Scanning with mirrorless cam and enlarging lens?

[Chan Tran]

For a lens of focal length f, and an extension past infinity of e, the magnification M is given by:

M = e / f

The distance of lens to image is: d_i = f + e.

These formulae agree with the ones given earlier in the thread if you do some algebra to rearrange them.

The difficulty with using the formula exactly is that the distance of lens to image is really the distance from rear principal point to the image, not the flange distance or the distance of the aperture from the image. But this is usually only a few mm off.

From this we can see that with your setup of a 50mm lens plus minimum 35mm extension past infinity, it would give a minimum magnification of 35/50 = 0.7x, which is a bit more than you wanted, so the 50mm enlarging lens plus bellows wouldn't be a good choice for duping 35mm onto APS-C.

In general, 50mm lenses don't provide a lot of working distance at magnifications near 1:4 to 1:1. If you want to do that, choices include: getting an SLR macro lens with a normal focus ring and some extension tubes; or using a longer f.l. enlarging lens on a bellows or similar; or buying a focusing helical mount and then messing around with a bunch of different adapters to get the extension within the travel of the focusing helical.

The op need a magnification of 1:7.6 which is in most macro lens range without any extension. The negative that the OP want to digitize is quite large 13x18cm.

 

[MattKing]

Why do you want to use an old enlarging lens on a new digital camera?

I'm thinking that a lens designed and optimized only for flat field performance at relatively high magnification is ideal for the purpose, and not often found as part of the regular lens lines for a modern APS-C camera.

 

[-chrille-]

Why do you want to use an old enlarging lens on a new digital camera?

This lens is a lot sharper than my Fuji lenses, even with a toilet paper roll extension tube and light leakage And I cant see any distorsion at all. And I already own it. But yes, it seems to have some limitations regarding working distance.

 

[reddesert]

The op need a magnification of 1:7.6 which is in most macro lens range without any extension. The negative that the OP want to digitize is quite large 13x18cm.

This thread is confused because the OP wants to use a camera (APS-C I think) to digitize roughly the range of (4x5 inch - 13x18cm) negatives as you say, while runswithsizzers asked about digitizing 35mm with APS-C. So there's two different magnifications running around, roughly 1:7 and 1:1.5. However the formula of

M = e / f

where e is extension past infinity can fairly easily answer the question for both. The enlarging lens way of doing this is tempting, but one needs to rig up some kind of focusing mechanism. Adapting an SLR macro lens, plus an extension tube if needed, is a good way to cover a large range of magnifications.

 

[mshchem]

This lens is a lot sharper than my Fuji lenses, even with a toilet paper roll extension tube and light leakage And I cant see any distorsion at all. And I already own it. But yes, it seems to have some limitations regarding working distance.

I got rid of my Fuji stuff. I had the 80mm macro lens it was amazing. I have an old Nikon 105mm Bellows Nikkor and a PB-4 bellows that on my D850 will focus from infinity to 1:1. I have the slide and film copying attachment for it as well. If you're going to go old school it's a good setup.

 

[runswithsizzers]

Why do you want to use an old enlarging lens on a new digital camera?

My Fuji X-T1 digital camera was already used when I bought it in 2019. This is probably one of the very few photo forums where that might be considered new.

Mostly, I bought the old enlarging lens to save money. That, and what @MattKing said in post #27.

At that point, I wasn't sure how well camera-scanning was going to work, in general -- and I wasn't sure what focal length I needed. So it seemed wiser to gamble less than $100 for an old enlarger lens and bellows, rather than $1200 for a new FUJIFILM XF 80mm f/2.8 R LM OIS WR Macro Lens.

The first enlarging lens I tried was a Schneider-Kreuznach Componon-S 5.6, 100mm, for which I paid $40. That lens worked very well for copying my negatives, though working distance was maybe a little long.

But now I use a Rodenstock APO-Rodagon D 75mm f/4.0 duplication/reproduction lens, which is excellent for my purpose! That one I found on eBay for $160(US). I wish I could afford to compare the image quality between the 75mm APO Rodagon and the 80mm Fuji Macro, but that test will have to be done by someone with deeper pockets than mine.

 

[xkaes]

Why do you want to use an old enlarging lens on a new digital camera?

"Because it's there!" -- George Mallory.

This seems workable with the correct adapter(s) and extension. Whether that will be the least expensive approach is another matter. An older, good, inexpensive macro lens with an adapter might end up costing more.

 

[runswithsizzers]

For a lens of focal length f, and an extension past infinity of e, the magnification M is given by:

M = e / f

The distance of lens to image is: d_i = f + e.

I was not familiar with: "extension past infinity" - but it looks like a very useful term. Thanks for that!

These formulae agree with the ones given earlier in the thread if you do some algebra to rearrange them.

The difficulty with using the formula exactly is that the distance of lens to image is really the distance from rear principal point to the image, not the flange distance or the distance of the aperture from the image. But this is usually only a few mm off.

Yes, this is the difficulty I have been having with trying to use the formulas. When we say "distance to lens" it is never clear which exact part of the lens the measurement is made from. While it may be only a few millimeters off, sometimes that few millimeters can be the difference between the lens being useful for my intended purpose -- or not.

I was hoping the formulas could be used to avoid the necessity of: buy-it-and-then-try-it; repeat as necessary. But when when the numbers are right on the edge between acceptable and unacceptable, theory fails, and it is back to the practical world. ;-)

 

[mshchem]

The issue isn't so much "enlarging" lens as much as, small sensor, short f.l., inability to change extension. Bellows and a nice Rodagon or Schneider or Nikkor enlarging longer ie 90mm - 150mm

I buy everything used so I didn't get killed on the Fuji lens.

Doesn't someone make a helical tube? 39mm????

 

[xkaes]

There are LOTS of places that have adapters. Try:

https://pixco.com.cn

They're solved my weird problems!

 

[-chrille-]

I have not seen any M39 adapters with helicoid focusing mechanism, only M42. I think it might be possible to use a M42 adapter with a threaded ring M42-M39 like this one which not build any length. https://www.amazon.se/M42-till-adapterring-objektiv-svart/dp/B00CGUMSRU

Another option is to still use a bellow at higher magnification and stitch multiple exposure of a plate. But that might be overkill in resolution and make large files and of course needs more time at the computer.

 

[reddesert]

I was not familiar with: "extension past infinity" - but it looks like a very useful term. Thanks for that!


Yes, this is the difficulty I have been having with trying to use the formulas. When we say "distance to lens" it is never clear which exact part of the lens the measurement is made from. While it may be only a few millimeters off, sometimes that few millimeters can be the difference between the lens being useful for my intended purpose -- or not.

I was hoping the formulas could be used to avoid the necessity of: buy-it-and-then-try-it; repeat as necessary. But when when the numbers are right on the edge between acceptable and unacceptable, theory fails, and it is back to the practical world. ;-)

The formula for extension past infinity is more or less exact (as close as needed, better than a mm certainly). The problem is figuring out where infinity focus is on say an enlarging lens, the distance to the principal plane. It's usually within a few mm of the aperture plane, but that isn't the same as the flange focal distance, which is just a detail of the mechanical body of the lens. You could even try to get it for some lens, say a Schneider 50/2.8 Componon, and discover that they changed the lens and body several times over 40 years of manufacture and the distance isn't always the same.

The reality is that for macro and copy work, you have to build a system that allows more than a few mm of focus travel so it has a margin for adjustment in focus and cropping. Bodging together a lens and bellows that barely reaches the magnification you want is a recipe for frustration.

I've been hinting at this already several times in this thread, but there are easier ways to do this:

- buy a nice used SLR macro lens like a Nikon 55mm manual focus (there are a zillion of these on the used market), an extension tube, and an adapter to your mirrorless camera. That lets you focus from 1:1 to infinity.
- use a longer focal length enlarging lens that provides more working distance, a bellows, and an adapter to the mirrorless.
- use the M42 focusing helicals you can get on ebay, an M42 extension tube set to vary the extension, an M42 to M39 adapter, and an M42 to mirrorless adapter. You still have to experiment with all the pieces to get the right extension, but at least they are inexpensive. The focusing throw of the helicals I have seen is short, so they are not as precise as a dedicated macro lens.