Durst L1200

[David Aimone]

Being somewhat new to this in my just completed darkroom, I actually used my Durst Enlarger yesterday for the first time, and I'm able to get decent results, but there seem to be a few unusual limitations that I wanted to ask about. It has the Varipoint Condenser Head on it.

First, with the varipoint light source, I can't seem to get the aperture closed down farther than about f/11 on the Schneider 105mm without all kinds of dark brown and blue distortions showing on the projection. Open f/11 and wider I can adjust the light source so it's fairly even. I have no idea what's going on here. Other enlargers that I've used haven't had this type of light source, so I haven't experienced this issue.

Second, when I'm trying to print on 5x7, it's very difficult to see the entire negative projected AND get it in focus. Also, the corners have less light than the middle. Should I try a lens other than the 150mm, or will that not help?

Third, when turning the enlarger "on", it takes anywhere from 1-3 seconds for the light to fully come one (less time if turned on very recently, more time if off for a while). Also, the bulb does take time to fade, but not as long. Is this normal? I seem to be able to guestimate times, but it makes it hard to use the 3 second interval method for burning and dodging.

I'm hoping this head with work for black and white printing. Otherwise, I might look for a CLS 501 head.

Any advice?

[gary mulder]

maybe you have the wrong condensers installed. 1 sec exposer is a quick way to zap your light bulb. Try leaving it on.

[David Aimone]

Gary,

I can double check, but I'm 99% sure it's the correct condenser assembly. The second part of your reply I don't quite understand.

David

maybe you have the wrong condensers installed. 1 sec exposer is a quick way to zap your light bulb. Try leaving it on.

[Nathan Potter]

David, I concur with Gary. Make sure the correct condensers for your particular light source are in place. If you are sure of this then I would suspect that you will need to adjust the distance between the lower condenser and the lens. At small apertures you are vignetting the illumination from the light source which results in the fringing (dark blue and brown shadow areas) in the projected image, just as you describe.

I am assuming that the varipoint light source is really an adjustable point source, so as you approach a true point source it becomes much more difficult to evenly illuminate the field of view of the film. However it should be feasible with a 150 mm enlarging lens. I can do it with both a 150 and 135 but with a hair of vignetting at the corners.

I believe Gary is suggesting that you run the bulb continuously while in use but toggle the light source using a shutter or a hand operated light block or some other mechanism. In such a case you will need to have a completely dark enlarger environment while the enlarger light source is on to avoid pre-exposing the paper.

My advice would be to increase the diameter of the light source to maximum (if this is really adjustable) since that will decollimate the illumination light and result in much reduced imaging of defects. Were you to use the light source at very small aperture you would need to be scrupulous about dust control.

Nate Potter, Austin TX.

[David Aimone]

Thanks, Nathan. I will try adjusting things again. I don't know if this is helpful, but I've taken a few photos of the setup on the head.





The second photo shows the varipoint bulb in the top of the head. The first photo shows the adjustment knob. The lower one moves the bulb front to back, while the upper moves it up and down and sideways.

The third photo shows the condenser arrangement. The 151 and 152 are stacked and the curved surfaces are facing each other.

Let me know if this helps.

Thanks!

David

[Donald Miller]

The point light source is very critical in it's focus. I have not worked with this particular source but I have converted a 138S into a point source and it is wonderfully sharp and very finicky on adjustment.

A 105 focal length lens is the wrong lens to use with the condensors that you have. Not only is the right focal length critical but on my 138S there is difference between differing manufacturers of the same focal length.

[David Aimone]

I'm sorry, that was a typo. I'm using a 150mm Schneider!

The point light source is very critical in it's focus. I have not worked with this particular source but I have converted a 138S into a point source and it is wonderfully sharp and very finicky on adjustment.

A 105 focal length lens is the wrong lens to use with the condensors that you have. Not only is the right focal length critical but on my 138S there is difference between differing manufacturers of the same focal length.

[Cor]

David,

I have the same enlarger (you removed the lid of the head which has a 45deg mirror, right?). I use a photcrescenta lamp such as:

http://www.photowarehouse.co.nz/bulb...otocrescenta-/

Not sure if I run a 150 watt though, might be 75 watt, anyway this lamp gives none of the problems you describe. A point source sound like a pain, not sure if it is really worth the hassle..

best,

Cor

Btw these lamps run for a long time, but perhaps stock up, tungsten bulbs like this are gradually phases out

[David Aimone]

Yes, the 45 degree mirror is there.

Cor, that link doesn't work. Do you have more information on the bulb type? Is this a non-point source type bulb?

[Cor]

That is weird, it works for me,
anyway try http://www.foto-r3.com/en/philips-ph...rger-lamp.html

or a Google search with photocrescenta.

These are ordinary tungsten light bulbs, but they are coated on the inside with some white powder, do not think that frosted is the right description.

The idea is that these lights have a very uniform diffuse spreading of light. I believe a frosted lamp can be used, but the printed label on the glass bulb can show up..

Best,

Cor

Btw they are not point sources

Yes, the 45 degree mirror is there.

Cor, that link doesn't work. Do you have more information on the bulb type? Is this a non-point source type bulb?