Upper bellows on Beseler 23C for 50mm lens

[Marco Buonocore]

I'm trying to help a friend set up his Beseler 23C for use with a 50mm lens for printing 35mm negs. I'm familiar enough with Beseler enlargers, and most have had a guide for the top bellows - for 4x5, 2 1/4 and 35mm etc... This enlarger does not have that guide.

So what I'm wondering is, where should the upper bellows be set for use for a 50mm lens? Fully extended?

Thanks!

 

[Doug Rhodes]

For 35mm the lamphouse needs to be cranked up as high as it will go, maximizing the distance between the lamp/condenser assembly and the negative holder. For 2-1/4x3-1/4 the lamphouse needs to be all the way down, bellows compressed, lamp/condenser assembly as close as possible to the negative carrier. Raising the lamphouse back up about 3/4" should optimize the light for 2-1/4x2-1/4 negatives. The total up and down range of the lamphouse is about 2-3/4".

Playing with the equipment (i.e. moving the lamphouse up and down with the desired negative and lens combination in place) should give you an idea of what the lamp and hemispherical lenses are doing, and where they need to be in relation to the negative in order to produce even illumination for enlarging. (The lens is not as much of a defining factor as the size of the negative, BTW.)

Hope this helps....

DR

 

[Marco Buonocore]

Oh that's great Doug, thanks for the input. Exactly the information I was looking for!

 

[smieglitz]

Is there an optical reason for not just leaving the condenser position set for the longest focal length? If the illumination is even over a 6cm x 9cm negative, I would assume it would also be even over a portion of that area (24mmx36mm) of a 35mm negative. Why move it?

 

[MattKing]

Is there an optical reason for not just leaving the condenser position set for the longest focal length? If the illumination is even over a 6cm x 9cm negative, I would assume it would also be even over a portion of that area (24mmx36mm) of a 35mm negative. Why move it?

Condensers are designed to "focus" the light to a point at or near the nodal point of the lens. So if you change the lens ....

 

[jose angel]

Marco, condensers have to be adjusted to concentrate the light beam over an area. Certainly you can successfully use the enlarger at the lowest setting with any format (maximum coverage), but if you set it to higher positions, the light will be concentrated on a smaller area, resulting in shorter printing times.