light leak from enlarger

[kmallick]

I am having a hard time identifying what is causing this light leak from my enlarger. I am using a LPL Saunders 6700 with color head. The picture below shows the light leaks which shows up as edges beyond the long side of the image projected from a 6x4.5 negative. I have checked the bellows and negative stage but cannot seem to identify the leak path. Does anyone here have any experience with this sort of light leak? Thanks in advance.

 

[MartinP]

Are they perhaps reflections from something shiny rather than a light leak, maybe a VC-filter holder round the enlarging-lens or something like that?

 

[Alpacaman]

I think I may have the same enlarger under slightly different branding, mine doesn't have this issue, and unfortunately I have no idea what would cause it, but I can give a stab in the dark. :angel:

Check that light is not reflecting off of the chrome rails that the bellows sit on (the ones with the small arc at the end). Maybe cover the rails and the bar at then end with masking tape to be sure.

The enlarger should have those sliding mask thingys in the negative carrier. As a workaround, could you use those to block out all light, along with light leaks, except the projected image?

 

[kmallick]

Thank you for all the tips and suggestions. They really helped me to think and look at things systematically. I spent a lot of time in the darkroom last couple of nights just trying to figure out where the light leak is coming from.

After looking at tit carefully, I found that the lines of light leak are actually on all four sides of the projected image.

It doesn't seem like a reflection or light leaking out from any gap. The problem seems to be coming directly from the lens. I am using a Rodenstock Rodagon-S 80mm f/4 lens. I don't have another 80mm lens to compare with. But I did switch it to a Nikon 50mm lens. It causes vignetting on the 6x4.5 and 6x6 negative but I didn't see the lines of light leak.

I could fix the light leaks by putting a dark skirt all around the lens or by hanging some black foam down from the negative carrier platform. But I am not very thrilled about this make shift fix as it gets in the way of reaching the lens aperture etc.

I am still puzzled as to what these lines that are being projected by the lens? Is it some sort of internal reflection or flare from the lens? I would be hard pressed to believe that the Rodagon lens is the culprit. But could it be? I have put my head on the baseboard to look up through the lens and I don't see anything suspicious to cause these lines. The lens is also mounted securely to the lens board without any gap.

Any tips or suggestions will be appreciated.

 

[pau3]

What kind of negative carrier are you using? If it is the universal carrier with blades,
maybe what you are seeing is the light coming from the other edge of the blades...

 

[kmallick]

I am using the standard glass less carriers made for LPL 6700 like here:

Here is a picture of the enlarger head (not mine, shamelessly copied from google image search):

The negative carrier fits into some sort of rails in the negative stage. I am wondering if my negative stage is missing some sort of baffle that prevents stray lights coming from the perimeter of the carrier.

Can someone with a LPL 6700 do me a big favor and take a close-up picture of the negative stage without the carrier. This would help me to see if I am missing some baffle plate or something. Thanks.

 

[Overkill-F1]

I can't believe the lens could be the cause.
The inner edges of the neg carrier could be the problem as suggested earlier. If the edges are 90 degrees to the negative (straight up and down), they could reflect light back through the lens and across the image.
I have filed the edges of my holders at an angle of 45 degrees or so and painted them flat black.
...Terry

 

[Pherdinand]

U know what..
I have VERY limited darkroom experience, but i have already noticed, that my LPL w color head is "leaking" light ... from the illuminated color scale windows! Seriously. I covered it with a red plastic (i only print bw) and since then, it's fine.

maybe this helps...

 

[kmallick]

U know what..
I have VERY limited darkroom experience, but i have already noticed, that my LPL w color head is "leaking" light ... from the illuminated color scale windows! Seriously. I covered it with a red plastic (i only print bw) and since then, it's fine.

maybe this helps...

I already did that. Like you I have used a black foam sheet to cover the front of the color scale. But that light leak is above the negative stage. The one I am seeing is coming from the lens.

 

[ChrisN]

Have you tried a test - put a lens cap on the lens, then make a test exposure onto a sheet of paper. If the line don't appear then the lens is the culprit. If the lines do appear, the lens is off the hook, and the problem is elsewhere.

 

[John Bragg]

long shot but is your easel reflecting stray light? I once had that problem with a shiny bevelled easel.

 

[kmallick]

I spent a lot of time tonight investigating the problem without luck. I am still pulling my hair out to solve it.

I blocked the window of the negative holder with black foam and the stray lines disappeared (along with the image of course).
The intensity of the stray lines of light also change with the aperture setting on the lens. Therefore, these are definitely passing through the lens (and not some reflections or light spill).

I have uploaded several pictures of the enlarger before and after I took off the Dichroic chamber to show you the details. I also have taken some pictures of the projected image with stray lines of light as I could record it in the dark. I have added some descriptions at the bottom of the pictures as well. You can start here and then scroll through the pictures:

Link

 

[Fred R.]

Link not working, yet. I'd like to have a go at solving this problem.

 

[MartinP]

Is it somehow overspill from the outer sides of the masking arms (assuming there are any) of the neg-carrier??

As a workaround, it may be possible to simply place black card or paper around the easel to reduce the amount of unwanted light bouncing around during exposures? Alternatively, is there a swappable light-mixing box which is accidentally the wrong one for this lens and format?

 

[kmallick]

Link not working, yet. I'd like to have a go at solving this problem.

oooops! fixed the link problem. here is a picture of the stray light.

 

[clayne]

Easel. Think about it. If you can see the light, it's because it's reflectance and not absorbed.