Joakim Målare
Established
Not entirely sure if this is the appropriate section to post this question in, but here goes...
I'm working on a modification for my enlarger - it's a Leitz Focomat 2c. For those of you who are not familiar with it, it's a well built auto-focus construction that does not by default allow the use of any enlarging lenses other than those designed for it. That's what I'd like to change.
Some time ago I got a Schneider Componon-S 5.6/100mm and a Componon 5.6/60mm. I also have an El-Nikkor 2.8/50mm. The 60mm shouldn't be a big deal to fit, but my goal is to fit the 50mm as well...
The 100mm turned out to be a M50 mount (I didn't look closely in the pictures when I bought it) but I'm pretty positive I'm able to squeeze it in there too.
I'm pretty far into the design and have solved a bunch of issues already, but since I'm not the super-technical genious when it comes to optics, I didn't realise when I started that all lenses aren't identical even though they go by the same "focal length". The 'flange focal distance' may differ, so I need to compare this for at least the lenses I'd like to use with the original ones on the enlarger.
It's fairly easy to find data for Schneider and Nikon lenses, but I need to know the flange focal distance for the V-Elmar 4.5/100mm and the Focotar 4.5/60mm. I'm not sure this data is online - so I was thinking perhaps I can measure it? Would it be as simple as projecting an image of the horizon on a plane and take a measure to the mounting flange?
Also, I have the flange focal distance for the Componon-S 100mm in M39 mount. Can I be certain it is the same distance for the same lens in M50 mount?
Thanks in advance for any feedback.
~ Joakim
I'm working on a modification for my enlarger - it's a Leitz Focomat 2c. For those of you who are not familiar with it, it's a well built auto-focus construction that does not by default allow the use of any enlarging lenses other than those designed for it. That's what I'd like to change.
Some time ago I got a Schneider Componon-S 5.6/100mm and a Componon 5.6/60mm. I also have an El-Nikkor 2.8/50mm. The 60mm shouldn't be a big deal to fit, but my goal is to fit the 50mm as well...
The 100mm turned out to be a M50 mount (I didn't look closely in the pictures when I bought it) but I'm pretty positive I'm able to squeeze it in there too.
I'm pretty far into the design and have solved a bunch of issues already, but since I'm not the super-technical genious when it comes to optics, I didn't realise when I started that all lenses aren't identical even though they go by the same "focal length". The 'flange focal distance' may differ, so I need to compare this for at least the lenses I'd like to use with the original ones on the enlarger.
It's fairly easy to find data for Schneider and Nikon lenses, but I need to know the flange focal distance for the V-Elmar 4.5/100mm and the Focotar 4.5/60mm. I'm not sure this data is online - so I was thinking perhaps I can measure it? Would it be as simple as projecting an image of the horizon on a plane and take a measure to the mounting flange?
Also, I have the flange focal distance for the Componon-S 100mm in M39 mount. Can I be certain it is the same distance for the same lens in M50 mount?
Thanks in advance for any feedback.
~ Joakim
Ronald M
Veteran
I don`t think you care about flange/focal at infinity. You care about it for the largest print you will make with it, ie enlarger head all the way up. That is what you design for.
I would set up a very small light to be the focus distance, then cut a hole in a large box to hold the lens, and then a paper to image the light. Measure the distance from focal flange to paper when the image is sharp. The box to light is same as lens to base with enlarger up all the way. Allow for negative carrier distance.
If you wish to make reversed column floor projection, that should be taken into account.
Another way is to make a sliding tube to make measurements from.
The bigger problem is getting the thing to AF properly. Changing the start point and more importantly the focal length requires a different shape to the AF cam.
I would set up a very small light to be the focus distance, then cut a hole in a large box to hold the lens, and then a paper to image the light. Measure the distance from focal flange to paper when the image is sharp. The box to light is same as lens to base with enlarger up all the way. Allow for negative carrier distance.
If you wish to make reversed column floor projection, that should be taken into account.
Another way is to make a sliding tube to make measurements from.
The bigger problem is getting the thing to AF properly. Changing the start point and more importantly the focal length requires a different shape to the AF cam.