L1200 lens panel for 40mm lens with M50 X 0.75 thread size.

[RobC]

Has anyone ever used a 40mm lens with an M50 X 0.75 thread size on a durst L1200 and which lens panel did you use?

I have a LAPLA 50 lens panel which the lens will fit but I don't know if I will be able to focus that without a recessed lens panel. Enlarger is packed away at the moment pending house move so I can't measure or check it out and am not going to buy the lens if I can't get right lens panel.

All the info I have found for 40mm lenses says use an LATUB lens panel which is recessed but only has a 39mm thread size which is no good and the only 50mm thread size is on the LAPLA which is a flat panel.

So would I be able to focus a 40mm lens using a flat panel on the L1200. I have my doubts and hence the question.

 

[ic-racer]

Hi Rob,
There are some variations in the "L1200." One L1200 Manual I have shows the same SETOPLA 2839 (recessed) board for BOTH 50mm and 35mm lenses. In the table, the longest lens associated with the LAPLA is an 80mm.

In another manual it shows the 35mm lens associated with a SEIPLA 7539. Yet, again 80mm is the longest lens for the flat LAPLA in that chart.

I think I'd look for a SEIPLA 7539 and 39mm mount lens.

 

[RobC]

but that is not an M50 X 0.75 thread size. I think that one is an M39 thread size.

Most 50mm and 35mm lenses use an M39 thread size. The particular lens I'm thinking of has an M50 thread size but I think it will require it to be recessed.

 

[ic-racer]

I updated the post above. Although there is no mention of a SEIPLA 7550 maybe it exists (M50x0.75 thread?).

With the Durst lens plates, sometimes it is cheaper to buy a lens that matches the lens plate.

Do you have the PDF manual? Would you like me to post the charts?

 

[RobC]

I do have a photocopy of the manual which came with my enlarger and some durst brochures and also a couple of L1200 pdfs. None of them show a recessed board with an M50 thread size. I don't know if such a thing exists. I also don't know if the lens would work with the LAPLA 50 flat lens board. I doubt it. I think I may need to get one made if I want to use this particular lens.

And yes the LAPLA 50 lens board is for much longer focal lengths than 40mm. The lens I'm looking at wasn't designed as an enlarging lens. Its thread size is bigger than what would be considered normal for a 40mm enlarging lens.

But if you do have a reference to a recessed lens board with an M50 thread size, then yes please do post the chart.

 

[ic-racer]

Just looked at a SEIPLA 39 I have here and it would be a pretty tight fit for a 50mm hole.

 

[RobC]

I thought so but that is becasue the recess is made in the knowledge that it will be using a narrower lens than the one I'm looking at using which is fatter.

OK I have done some digging/unpacking and have managed to take some measurements and check lens measurements/design/specification diagram.
My Rodagon 35mm lens mounted on a flat panel would put the rear element around 35mm from the film plane with the focus as close as it will go. This 35mm lens would certainly need its recessed lens panel and not the flat panel.
However, the 40mm lens I'm thinking of buying and used on a flat panel with focus fully up would put the rear element only 8mm from the film plane. The lens design is very different and protudes much further past the lens panel mounting flange than a normal enlarging lens does.
At 8mm I think, having checked some more numbers with pre-designer lens software and checked the lens spec carefully, that my LAPLA 50 flat lens panel will work plenty well enough with room to spare. So my concerns were unfounded.

 

[RobC]

The next and very big hurdle to overcome is being able to put the enlarger head at a height which won't cause the foot of the column to protude into the intended image size. This may require turning head horizontally but I would like to avoid that if at all possible. More calcs required and possibly a custom made work bench. Oh the joys of traditional darkroom printing

 

[ic-racer]

Good point on the flange-focal distance. Like the Minolta CE 35mm lens has a long flange-focal distance and a good portion of the lens pokes up into the bellows.

 

[Ronald Moravec]

If the 40 mm is a wide angle for 135 film and it is a condenser enlarger , it probably will not work well off center point. I have several WA enlarging lenses that work perfectly on diffusion, and not worth beans on condensers.
I can not explain why, just that they do not work toward edges..