Advice on reducing the light output of a 40 year condensing enlarger

Marcust101 · Aug 21, 2007

Hi folks,

My first post here but I've been enjoying the site for some time.
I have recently laid my hands on a 40 year old Raj 5 enlarger made by Leisgang

It works fine and the lens is good after a clean but I've found the light output is resulting in me having to stop the lens to F22 or more to increase the exporsure times into more than 10 seconds. It takes a screw-in standard bulb at 150W, I've tried lower wattages but the evenness of the light drops dramatically.

Does anyone know of a bulb type I should be using or perhaps a piece of ground glass showwhere in there would even things out. The condenser is easily accessable and can be removed and modified.

Any suggestions appreciated

Many thanks

Marcus

Roger Hicks · Aug 21, 2007

Dear Marcus,

First, welcome.

Is there no way to raise/lower/decentre the bulb? Most are on a post, usually secured by 3 screws, and can be moved up and down and 'wiggled' quite a bit to get more even illumination.

I assume you're using enlarger-type bulbs with no writing on them? If the above is possible, a direct swap for a 75 should be feasible.

Cheers,

Roger

jeroldharter · Aug 21, 2007

An easy alternative would be a 3-stop (8x) neutral density filter on the enlarging lens.

David A. Goldfarb · Aug 21, 2007

Or better--a ND gel (lighting gels are adequate) between the bulb and the condensors, so it's not in the image path.

Marcust101 · Aug 21, 2007

Folks,

Thanks for the answers so swiftly.

The enlarger does have a pole with wiggle room and it is an unmarked bulb, I'll take a look round Dublin for a 75W bulb. I have a clearance problem as my darkroom is a coverted shed and I'd rather not put the unit on the floor, perhaps a low shelf though.

some kind of ND filter / gel is a good idea too, I'll pick one up and try it

Thanks for your help

Marcus

Roger Hicks · Aug 21, 2007

Marcust101 said:
Folks,

Thanks for the answers so swiftly.

The enlarger does have a pole with wiggle room and it is an unmarked bulb, I'll take a look round Dublin for a 75W bulb. I have a clearance problem as my darkroom is a coverted shed and I'd rather not put the unit on the floor, perhaps a low shelf though.

some kind of ND filter / gel is a good idea too, I'll pick one up and try it

Thanks for your help

Marcus

It'll probably be further down with a 75 watt so you'll have more clearance.

Marcust101 · Aug 21, 2007

Thanks Roger, I've sourced a bulb in John Gunn's Camera Shop in Dublin (highly recommended if you're in Dublin and need something not digital)

I'll let you know how I get on

regards

Marcus

Shawn Dougherty · Aug 21, 2007

Welcome, Marcus. Good luck with the printing! Shawn

max_ebb · Aug 21, 2007

You could use some kind of variable resistor like a dimmer switch, but then you'd need a voltage meter for consistency/repeatability. I assume the variable resistors made for condenser heads (like the Beseler Resistrol) are just glorified dimmer switches with voltage meters attached.

GeorgesGiralt · Aug 21, 2007

hi Marcus !
I do not advise for the light dimmer. Thie kind of bulb will give very less warm light and you may have some trouble with the variable contrast filters.
If you've access to the condenser, I sugest to install a tracing paper sheet into the light path. This will make the light more diffuse but will reduce the light output drastically. Once you've got the proper place for the drafting paper you can replace it by a sheet of glass which will be frosted using valve grinding paste from a car overhaul shop. 1à minute work and you're done.
I think I've seen the enlarger you're referring and I wonder if it was made to take 150 w bulb ? Look at the designation plate or try to contact Liesegang in Germany I think they are still in business.
Hope this helps.

Marcust101 · Aug 22, 2007

Thanks for the suggestions and support folks, I' doubt the 150W is intended for use in the enlarger but my local shop is getting me a 75W. I will try the tracing paper/frosted glass route as well, and let you know how I get on

thanks

Marcus

fschifano · Aug 24, 2007

Inline variable resistors are definitely a bad idea if you're planning to use variable contrast papers. Contrast will change for a given filter with the changing color temperature of the lamp. Using an out of spec light bulb can be a problem as well. The entire optical system of the enlarger is often designed around the bulb being of a certain size, shape, and filament position. Some enlargers have adjustments to compensate. Others do not. Still others are not as sensitive to these changes within certain parameters. Assuming that everything is within spec and you are still getting too much light, the easiest, and least problematic way of reducing the light output is by the use of a neutral density filter. My preference is to use a lighting gel in the filter drawer if possible. If there is no filter drawer, it should be possible to use one directly over the condenser since these gels are designed to withstand a fair amount of heat. Rosco makes them and you can read about it here: http://www.rosco.com/.

Paul Howell · Aug 24, 2007

You can sandpaper off the logo and printed info on a standard 75 white bulb, I dont recall what kinds of bulbs are available on your side of the world, but here we have bulbs that are sort of gray and more expensive white bulbs. If you have a light bulb shop in Dublin that specializes in lighting you ought to be able to order the correct photo bulb as well.

Marcust101 · Aug 27, 2007

OK I got the right bulb from Gunn's on Camden street (for those who made need a decent old camera shop in Dublin). It took the output down a stop but I'll need to reduce some more. I'm going to add a piece of ground glass under the condenser and see how that works.

Thanks for the help folks

Marcus

gminerich · Aug 27, 2007

Hi:

Instead of an ND gel you can try a piece of fine mesh, black (non-galvanized) steel window screen (hardware cloth). That should give you a good light reduction at an affordable cost.

Marcust101 · Sep 10, 2007

Ok, an update

I've gotten a 75 W bulb which helped and added a piece of Satin finished glass, (lightly ground and polished) under the condender unit above the negative.

This combination has reduced the output by 2-3 stops, some more scientific testing to follow.

The piece of glass was €9 so an affordable solution i the end.

Many thanks to you all for your help

regards

Marcus

Advice on reducing the light output of a 40 year condensing enlarger

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