Scanning with mirrorless cam and enlarging lens?

[-chrille-]

I want to use a Fuji X-T3 camera and a Schneider Componon-S 50mm f/2.8 enlarging lens for scanning collodion wet plate tintype and ambrotype plates.

How do I calculate the distance needed from lens to camera sensor if I want, for example, a 13x18cm plate to fill the whole field of view?

I have built a permanent ”scanning” rig using an old Meopta Axomat enlarger which I have mount a tripod head on. The distance from tripod head/camera to enlarger baseboard is adjustable approx. 300mm.

 

[koraks]

Formula/computation for enlarger magnification?

I'm currently doing wall projection, up to 30" or so. I'm planning on tearing up the darkroom to reach around 6' enlargements. 4x5 negs with 135 and 150mm glass (the 150 is a Rodagon "G", we'll see if I need it at these sizes). Anyway, to aid in planning - is there a way to compute...

www.photrio.com

 

[-chrille-]

Thank you

 

[runswithsizzers]

In the link provided by @koraks, @Nodda Duma gives a formula, which I will reproduce here:

---
Width of your desired print h(i), distance to wall d(i), width of negative, h(o) and distance to negative d(o) gives you magnification:

M = -[d(i)/d(o)] = h(i)/h(o)

and then also focal length.

f = d(i) * M / (1 + M)

Btw, the negative sign just means the image is inverted (naturally)
---

Can anyone please clarify, How is "distance to wall d(i)" measured? That is, Is that the total distance between the wall and the negative, or the distance between the wall and the lens, or...?

Thank you.

 

[xkaes]

The OP is asking for the distance from the lens to the "film", not the distance from the lens to the subject.

 

[_T_]

Can anyone please clarify, How is "distance to wall d(i)" measured? That is, Is that the total distance between the wall and the negative, or the distance between the wall and the lens, or...?

Thank you.

Both the di and do measurement would be from the flange. With large format cameras this flange is measured from the subject facing surface of the lensboard. I'm guessing it's the same for an enlarging lens? I'm not sure, I've never measured one. With some lenses, including nearly all SLR lenses, it is difficult to know exactly what point constitutes the flange for the purposes of doing these calculations.

That said, frequently the marked specifications of a lens do not align exactly with its physical properties. While the formulas listed above can get you in the right area you're usually going to have to fiddle with the setup a little bit to get the framing exactly right. So it may not be of great importance that you measure from exactly where the specific optical formula dictates the flange to be.

The OP is asking for the distance from the lens to the "film", not the distance from the lens to the subject.

The formulas listed can be used for both of these calculations.

 

[xkaes]

The formulas listed can be used for both of these calculations.

I realize that. I doubt that the OP does.

 

[runswithsizzers]

I see my question was poorly worded, and partially answered by @Nodda Duma. So there are two "d"s:
d(i) is distance to subject, and
d(o) distance to negative
... apparently, both are measured to some part of the lens. Is the "flange" is the same as the lens mount?

quoting @_T_ "While the formulas listed above can get you in the right area you're usually going to have to fiddle with the setup a little bit to get the framing exactly right. So it may not be of great importance that you measure from exactly where the specific optical formula dictates the flange to be."

I agree that the approximate measurements are close enough for most purposes. I was hoping to use the formulas more precisely for a macro setup -- copying film with an enlarger lens. For that use, it is possible that the combination of the fully closed bellows and any needed lens adapters between the camera and the lens might add up to some minimum d(o) that would provide more magnification than desired, depending, of course, on the the other variables (focal length, film format, and camera sensor size).

 

[gary mulder]

The actual focal length of a Componon-S 1:2.8 50 mm is 52.6 mm and the Internal nodal separation (HH’) is -6.5

 

[_T_]

I agree that the approximate measurements are close enough for most purposes. I was hoping to use the formulas more precisely for a macro setup -- copying film with an enlarger lens. For that use, it is possible that the combination of the fully closed bellows and any needed lens adapters between the camera and the lens might add up to some minimum d(o) that would provide more magnification than desired, depending, of course, on the the other variables (focal length, film format, and camera sensor size).

When you’re dealing with such a narrow depth of field it is not possible to focus a camera by mathematical formula. You have to look at the focus peaking on your mirrorless and you will probably have to refocus your system every time you get ready to scan another batch.

 

[runswithsizzers]

When you’re dealing with such a narrow depth of field it is not possible to focus a camera by mathematical formula. You have to look at the focus peaking on your mirrorless and you will probably have to refocus your system every time you get ready to scan another batch.

Yes, I agree, any attempt to focus by numbers in a macro situation is highly unlikely to be successful. Focus peaking on my Fuji X-T1 works pretty good.

My interest in d(o) was to help make decisions about which parts to buy to put together a camera scanning rig. In other words, to help predict which parts might work together to get the magnification I want.

For example, to photograph a 135 negative, I calculate it requires a magnification of about 0.656x to fill the sensor of my APS-C camera. [135 negative width = 36mm, Fuji X-T1 sensor width = 23.6mm, and 23.6mm / 36mm = 0.656]

I am using a Pentax screw mount bellows with an adapter on the back for my Fuji APS-C camera. And another adapter on the front to mount the enlarging lens. When the bellows and adapters are mounted on the camera, it's about 85mm from my camera's sensor to the surface where the back of the enlarger lens will mount. That's with the bellows fully closed, so the back mounting surface of my enlarging lens cannot be any closer to my sensor than 85mm.

The question I was trying to answer is this:
Given that unavoidable minimum of 85mm extension, is it possible that a 50mm enlarging lens might provide more magnification than my target of 0.656x? If so, this would result in unwanted cropping of the negative, making a 50mm lens unsuitable for my purpose.

I ended up buying a 75mm lens and it works fine -- probably better than a 50mm would have. But it bugs me that I never was able to figure out if a 50mm would have worked.

@-chrille- Were you able to use the formulas to answer you question?

 

[-chrille-]

I did a setup but using a 4x5 plate. I got 36mm by numbers. I cut a toilet paper roll as a tube and by trial and error I get a distance from camera mounting flange to lens screw mount(incl threads) of 30mm. The field of view I get is a bit larger than plate and some cropping is possible.

A bellow would be a better option to adjust for different plate sizes on the baseboard but I dont think there are bellows that short available.

Will buy a Fuji X to M39 adaptor and see if I can find extension rings to adjust to the correct distance or build my own with step up/down filter rings.

 

[Chan Tran]

All the calculation is not exact because you don't know where the front and rear nodal plane of the lens are at. The calculation assumes they are the same. But if the OP has the lens it's simple just trying it out. That's the best way.

 

[runswithsizzers]

@-chrille- "A bellow would be a better option to adjust for different plate sizes on the baseboard but I dont think there are bellows that short available."

I suspect you are right about that. Fully closed, my Pentax bellows are about 38mm in thickness, without any adapters.

One solution which will get the lens farther away from your camera (at the same magnification) would be to switch to a longer focal length lens. But you already have a pretty nice lens, so you are probably not eager to spend more money on another one.

 

[xkaes]

I did a setup but using a 4x5 plate. I got 36mm by numbers. I cut a toilet paper roll as a tube and by trial and error I get a distance from camera mounting flange to lens screw mount(incl threads) of 30mm. The field of view I get is a bit larger than plate and some cropping is possible.

Uh, your 50mm lens should need about 50mm of space between the film and the lens at infinity. Closer than that -- which is what you are doing -- is even more extension. So something is amiss.

Also, your 50mm lens won't cover much more than 24x36mm at infinity. To cover 4x5 you've got to add quite a bit of extension. My guess would be that you need about 140mm of space between the film and the lens to cover 4x5 -- but that's much more magnification than you likely need.

All of this suggests to me that there are lots of bellows that would work for your subjects and that lens -- but I don't know the size of your subjects.

 

[Chan Tran]

I tried it with my Nikon and the EL Nikkor 50mm f/2.8 and Nikon PB6 bellow. The shortest distance from lens flange to sensor I can get with this combo is about 100mm and the magnification is right around 1:1. The Fuji would have shorter flange distance than the 46.5 mm of the Nikon.

 

[-chrille-]

Uh, your 50mm lens should need about 50mm of space between the film and the lens at infinity. Closer than that -- which is what you are doing -- is even more extension. So something is amiss.

Also, your 50mm lens won't cover much more than 24x36mm at infinity. To cover 4x5 you've got to add quite a bit of extension. My guess would be that you need about 140mm of space between the film and the lens to cover 4x5 -- but that's much more magnification than you likely need.

All of this suggests to me that there are lots of bellows that would work for your subjects and that lens -- but I don't know the size of your subjects.

No, it works. The size of my subject is 4x5.

 

[Chan Tran]

I think the amount of spacing you need is 39mm.

 

[xkaes]

Since you are using a half-frame camera your magnification is pretty low. That changes everything -- so you won't need much extension. A very short extension tube might be all you need. Maybe a helicoid, variable extension tube?

 

[Chan Tran]

Since you are using a half-frame camera your magnification is pretty low. That changes everything -- so you won't need much extension. A very short extension tube might be all you need. Maybe a helicoid, variable extension tube?

I figured he only needs about 39mm of extension from the lens to the camera flange. The distance from the lens to the sensor is about 57.5mm. That is with my bellow I can't do it because the minimum extension of the bellow it too much.

 

[xkaes]

I figured he only needs about 39mm of extension from the lens to the camera flange. The distance from the lens to the sensor is about 57.5mm.

And a lot of that space will be takes up by the adapter(s).

 

[Chan Tran]

And a lot of that space will be takes up by the adapter(s).

Yes the flange distance of the Fuji X series is 17.5mm I think so about 39mm or so would be the adapter and extension. Really no room for a bellow. I know the OP already has the 50mm lens but I would be much easier if a longer focal length lens is used.

 

[xkaes]

My Minolta Compact Bellows is 40mm when collapsed, and I don't know of any shorter than that.

 

[reddesert]

The question I was trying to answer is this:
Given that unavoidable minimum of 85mm extension, is it possible that a 50mm enlarging lens might provide more magnification than my target of 0.656x? If so, this would result in unwanted cropping of the negative, making a 50mm lens unsuitable for my purpose.

I ended up buying a 75mm lens and it works fine -- probably better than a 50mm would have. But it bugs me that I never was able to figure out if a 50mm would have worked.

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.

 

[mshchem]

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