Condenser Lenses for Durst 138S

[ajeddeloh]

Hi everyone!

So a while ago I got a Durst 138S for free off Craigslist and finally got set up to use it today (first prints!). It came with two condenser lenses, a Latico 240 and 240R and two enlarger lenses a 190mm and a 70mm. Reading the manual, it appears you need specific condenser combinations for different length lenses. With the 240/240R any short lens (i.e. one that offers a lot of enlargement) vignettes like crazy. I can do 5x7 and maybe even 8x10 prints with the 190mm lens (35mm negative) but if I wanted to go larger, I'd need a new condenser lens. On ebay right now there's a pretty cheap 130. The manual doesn't suggest a combination for a 70mm lens, but for a 60mm one it suggests a 130 and an 85 while for 80mm it suggests 200 and 130. Could I get away with using a 240 and 130?

 

[ic-racer]

Aristo used to make a coldlight that fit in place of the condensers. With that combination you could use any lens.

 

[Luis-F-S]

Yup the D57. I bought one in 1998 from Calumet. Now you need to find them at auction. Can't help with the condenser combinations, don't have a 70 and have all the condensers.

 

[ajeddeloh]

Is there an advantage to using a condenser lens setup instead of diffuse light from one of those lights (i.e. why bother manufacturing it with the condenser setup if the other is easier)?

 

[ac12]

The manual won't have all focal length lenses. For the missing lenses, you have to take the closest lens in the table (preferably longer), to determine the condenser combo to use. For the 70mm, I would use the condenser combo for the 80mm lens.
And yes you will have to buy the missing condenser lenses. Put that into your budget. I had to do same for my L-1000.

 

[chrisaisenbrey]

Well the 190mm lens is quite extreme for a 35mm negative. I guess you need you have to lower your base plate quite a bit.

However I wonder why you get vignetting with the big condensers.

What kind of light bulb do you use? Durst recommends special big frosted light-bulb of 110mm diameter for some setups. The setup provides then partly diffuse light.

They are of cause difficult to find. You can try to use some opal plate in your filter drawer. In the housing of a 138 there is plenty of space for some diy.

Chris

 

[quine666]

The 240/130 combination is intended for a 105mm lens -- it will be a stretch for 70mm. You might be able to make it work at certain magnifications by adjusting the bulb position (the condensers must project the bulb onto the rear nodal point of the lens to get even illumination, so the focal length of the condenser combination has to be appropriate for the distance from the lens to the negative carrier).

 

[ajeddeloh]

Do you think I could use my 135mm prime from my camera as an enlarger lens in that case (with the 240/130)? I'd have to buy/build an adapter, but other than the mount is there any major difference between an enlarger lens and a camera lens?

On a more theoretical level, what goes into determining the combination? Like why 240/130 for 105mm?

 

[ic-racer]

Is there an advantage to using a condenser lens setup instead of diffuse light from one of those lights (i.e. why bother manufacturing it with the condenser setup if the other is easier)?

$$$
Condensers are very efficient allow for one to use lamp that was at the time inexpensive and did not require a separate power supply. Now, the correct large opal enlarger lamp for the 5x7 condenser setup can cost a lot! Assuming you can find one.

 

[quine666]

The condenser number refers to the nominal diameter of the glass in mm (the larger ones are cut down to fit inside the box). The lower condenser must be large enough to cover the area of the negative that you want to enlarge. The upper condenser is typically at least as large as the lower condenser, and the focal length of the combined system must be able to hit the rear nodal point of the lens when you position the bulb. I don't know how the focal lengths work exactly, but the larger condensers generally have longer focal lengths, and the 240 is available in multiple focal lengths (240, 240R, 240H, 240P). It seems plausible that a smaller lower condenser would be more efficient WRT light output as long as it covers the negative.

FWIW, I've never had problems using the smaller and commonly available PH211/212/213 bulbs in the 138 types (just pay attention to the bulb position).

 

[quine666]

One other thing: the smaller bulbs yield higher contrast than the larger bulbs because the light is more collimated.