Point source enlargers. Refocusing condensers and lamp question.

I have the urge to convert a long discarded enlarger of mine to a point source condenser. (Once I've cleaned the cat hair and afterbirth from it. ...but that's another story.)

Firstly: How do you refocus the condensers? Are the pair moved back and forth from the film plane or is the distance between the pair adjusted? How fine does the adjustment need to be?

Secondly, what lamps are traditionally used as a light source? Do you think a single white LED would cut it?

I've tried this.

Is your existing enlarger a condenser enlarger?

Most so called condenser enlargers are really condenser / diffuser and so have no condenser movement. The best pattern is probably the the old mahogany horizontal enlargers of 100 years ago. These had the condensers separated from the lamp housing often with separate bellows or a sliding metal cylinder.

To make the adjustments you need to move both the condensers and the position of the bulb. I kept the condensers together as a pair.
Moving the condensers (a bit) is to focus the filament image onto the front of the enlarger lens to ensure maximum light is going through the negative. Maybe not so critical if you are using one size of negative and making similar sized enlargements.
Actually, the bulb is the most critical thing - the bulb needs to be at the focal point of the condensers and needs to be moved as the enlarging lens to negative distance is changed when focussing.

I used a halogen lamp of about 50 watts with a mask in front of it with a small hole (about 3mm). Mechanical challenges involve holding the bulb nice and central whilst allowing it to slide up and down this axis.

Interesting, though. The difference in the resulting images I got was striking. Very gritty and contrasty compared to the condenser / diffuser type, which is only a little different to the diffuser type.

Ultimately a pain, though, to set it all up and not to get big kidney shaped 'blobs' due to misalignment. I did experiments, had fun, then went back to my opemus enlargers without finishing anything.

How much adjustment is a 'bit'. An inch or so? A centimetre? A spider's leg?

cinefane said:

I have the urge to convert a long discarded enlarger of mine to a point source condenser. (Once I've cleaned the cat hair and afterbirth from it. ...but that's another story.)

Firstly: How do you refocus the condensers? Are the pair moved back and forth from the film plane or is the distance between the pair adjusted? How fine does the adjustment need to be?

Secondly, what lamps are traditionally used as a light source? Do you think a single white LED would cut it?

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The following is from the Durst Varipoint (point source) enlarger manual:

3.3 Black-and-white enlarging with the Varipoint 1200
Check for evenness of illumination
*Switch on enlarger lamp

For unit version equipped with OPTO-TIM press "Light" key
*Open LENS diaphragm fully

Lamp centering:
If there are shadows on the baseboard, center the lamp as follows:
*Turn knobs 103 and 105 until projection is free of shadows.
*Turn lamp and adjust horizontally (103 = horizontal adjustment, 105 = vertical adjustment)

NOTE: do not stop down the lens!

Click to expand...

Here is a picture of a Durst Varipoint bulb:

I converted an old federal enlarger to point source. In most of the Federals the blub can be move up and down, I use a clear 100 watt hologen bulb. My Federal is not ideal as it has only a single condenser, but I have taken the time to hunt down a double condenser model.

Paul

cinefane said:

How much adjustment is a 'bit'. An inch or so? A centimetre? A spider's leg?

Click to expand...

It depends what you are trying to adjust for.

The early wooden horizontal enlargers with their spirit lamps etc, were designed to accommodate various plate sizes and had the disadvantage of a relatively feeble light source, so some had condensers that could move quite a bit ( a few inches I suppose) to ensure they just covered the required negative and give maximum illumination. I have an early enlarger of this type and it also has the option to change the condensers.

If you are sticking with 35mm (or medium format) and have a reasonably powerful light source then I think the most important thing is a moveable and adjustable light source. If you kept the condensers fixed in position (where they probably are now) then the disadvantage is that as you move the light source nearer or further away then the cone of light going through the negative changes size, too. This means the intensity and hence the exposure is all over the place as you change image size - but if you are using a meter it may not really be much of a problem. I haven't seem any modern point source condenser heads but it wouldn't surprise me if the condensers were fixed - or at least only designed to be tweaked during initial set-up.

cinefane said:

I have the urge to convert a long discarded enlarger of mine to a point source condenser.

Click to expand...

Hans Namuth was big on point source enlargers. If you find the old Darkroom and Darkroom 2 books from Ralph Gibson's Lustrum Press, he talks a lot about how and why he uses them. I got my copies on Amazon used for less than $10. If you can find it, PM me and I'll send you a scan.

Back in the 70's and 80's I had a point source Large format enlarger it ran with a 275w photoflood bulb, each new bulb needed adjustment and they only lasted a few exposures, the lamp housing was quite long (just under a meter) and had a baffle to prevent light bouncing down the side even though they were matt black Should add the enlarger was horizontal and mininum typical enlargement was 24" and maximum about 16ft.

Ian

My varipoint has been sitting on my bench for years now, without being used. Not is the time for me to give it a go, but all the good information on point light source enlargers has disappeared with the end of durst-pro-usa. Does anyone happen to have saved these PDFs? If someone has a users manual for the Durst Varipoint it would also be much appreciated.

Perhaps I should have started a new thread and not resurrected this old one? Apologies if that's the case. It's my first post.

No apology necessary.
Welcome to Photrio.

New Thread started for you over here: https://www.photrio.com/forum/threads/user-manual-for-durst-varipoint.211520/

Not only do you have to move the point light source up & down (relative to the condenser) in order to get the light as even as possible (which is very difficult in part because the lens is always used wide open), you have to move the bulb left/right and forward/backward to get it centered. That means you have to allow 3D movement of the bulb. Good luck with that.

My DYI point source I could only move the bulb up and down, still I was able to get good results, after all that I found the prints to be too grainy and had to print grade 00 to 1. I think for a point source to work well you need to develop your negatives to match the light source. As I recall the Omega point source head was intended to print microfiche. But AA had a point source for his Besler 45 and I read that he used it for 35mm.

We had an old (Leitz?) condenser enlarger in our school darkroom in the 1960s. If I recall correctly, the condenser was fixed in place, but you needed to adjust the height of the bulb above the condenser whenever you changed enlarger height. The bulb was held on the end of a steel tube co-axial with the condenser and lens. So the axial position was fixed, but the bulb to condenser distance was variable, with a grub screw to hold the tube in position. (It was ridiculously easy to smash the bulb on the condenser too!) Prints from that enlarger were very stark, very 1960s, and IMHO horrible. I can't imagine why anyone would want to go back to that aesthetic, but I guess it will be a fun exercise.

Paul Howell said:

I think for a point source to work well you need to develop your negatives to match the light source.

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That's true of any enlarger head. If a diffusion head is used, the exposure and development needs to produce a negative with a higher contrast index than if a condenser head is used. A point light source is great if you want higher contrast.

I thought I would like it, turns out not so much. I gave the DYI version I made to a friend, she got really good results with it, not sure what happened to it as she moved and I lost contact with her.

snusmumriken said:

the condenser was fixed in place, but you needed to adjust the height of the bulb above the condenser whenever you changed enlarger height. The bulb was held on the end of a steel tube co-axial with the condenser and lens. So the axial position was fixed, but the bulb to condenser distance was variable, with a grub screw to hold the tube in position.

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I used to have an old Liesegang enlarger that worked this way. It produced the crispest prints I ever saw. Man, there's no way I'll ever manage to get a truckload of dust printed that sharply. It was gorgeous. If you liked dust.

I still have this half-baked plan to try something along these lines in color on my Durst 138 with a couple of 3W LED beads. Should be...interesting.

Thanks everyone. The reason for the point light setup is a series of negatives i shot, pre-flashed low density and low contrast 4x5” night shots.
Ordered a bunch of books recommended on this forum about the point light setup.

I also recall some good info on durst-pro website. I ordered some parts for an 8x10” enlarger from him a while back, but they never arrived.

Ulrix said:

Ordered a bunch of books recommended on this forum about the point light setup.

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Care to share the titles of the books you found useful?

I've been using a point source enlarger to enlarge digital negatives. You can use regular condenser sets and they are extremely efficient. I started out with a 150watt projector bulb and would easily expose a 8x10 lupex contact paper from medium format negative in under a second. I downsized to a 20 watt bulb and still use a 3 stop ND filter for 11x14, most likely I am going to set up a 5 watt source.

If you want to mess around with it you just need a condenser enlarger and the ability to adjust the distance of the bulb to the condensers.

The high contrast part is quite true you need N-2 negatives to make it work. This works for me because the images are digital and I can tailor the negatives to any contrast I like.

What enlarger do you use? I used a Federal 6X9. First attempt was with a single condenser then I got a double condenser model.

avandesande said:

I started out with a 150watt projector bulb and would easily expose a 8x10 lupex contact paper from medium format negative in under a second. I downsized to a 20 watt bulb and still use a 3 stop ND filter for 11x14, most likely I am going to set up a 5 watt source.

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The Beseler Point Light Source uses a small 150w 24v halogen bulb. I have it attached to a rheostat to dim it to increase the exposure time and improve the focusing -- but the light gets very yellow.

xkaes said:

The Beseler Point Light Source uses a small 150w 24v halogen bulb. I have it attached to a rheostat to dim it to increase the exposure time and improve the focusing -- but the light gets very yellow.

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I have a stepdown transformer as well that I am using even with the 20watt bulb. The problem is that when you turn it way down it makes it hard to use multigrade filters because of the spectrum. That is why I have been using lower output bulbs and ND filters.

Paul Howell said:

What enlarger do you use? I used a Federal 6X9. First attempt was with a single condenser then I got a double condenser model.

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I have a omega D2 head that I have been resting on my Besselar 45 negative stage to make exposures. It's crude but it works. If I really want to go this route I will buy a dedicated D2 but this will also require knocking down a wall and enlarging my darkroom to make space for a second enlarger.

avandesande said:

I have a omega D2 head that I have been resting on my Besselar 45 negative stage to make exposures. It's crude but it works. If I really want to go this route I will buy a dedicated D2 but this will also require knocking down a wall and enlarging my darkroom to make space for a second enlarger.

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I have a D3, same head as the D2, I need to take a look at the bulb, after 50 years did not know that it could raised and lowered. I have s pdf user manual need to reread it.

avandesande said:

I have a stepdown transformer as well that I am using even with the 20watt bulb. The problem is that when you turn it way down it makes it hard to use multigrade filters because of the spectrum. That is why I have been using lower output bulbs and ND filters.

Click to expand...

At least the yellow reduces the contrast -- without any filters.