Can lenboard cause light leak?greenspun.com : LUSENET : Large format photography : One Thread
Can lenboard cause light leak?
Hello, kind and experienced photographers, I am being driven mad by white lines on my negs, I was generosly given a lot of advice in pevious post which I made regarding this problem. Here is a sample image :
I have checked the bellows for leaks, checked the mounting of the bellows, used various filmholders and films, carefully shaded the filmholders at the time of exposure until I am sure that no light is is leaking in throught the back of the contraption.
The latest results are completley free of leaks apart from the fine white line around the image, could this be the lensboard? is it worth changing it, or should I give up and take it to a technician?
-- adrian tyler (email@example.com), February 24, 2002
Hmm, those are odd light leaks, such confined lines. I am assuming they are not contrails . .
Lensboards can indeed cause light leaks. I have to tape up my deardorff boards each time. It's easy to test. Remove the back of your camera and in a dark room stick a 60 or 100 watt bulb in the bellows (not for long- it gets hot) with the lens on. This is easier in an 8x10 camera.
But I don't think those leaks are from the lensboard. I don't think a lensboard leak would cast such narrow beams of light.
Do some more tests tonight when it gets dark (or in your darkroom) and you'll get the answer.
-- Erik Ryberg (firstname.lastname@example.org), February 24, 2002.
Adrian: I've looked at your photo and I also vote for jet contrails in the sky as the most likely explanation. First, they look like contrails. Second, they end at the edge of the building, which a feature in the distance will do, whereas a light leak would just go across every part of the image indiscriminately. There are times when contrails can appear rather noticeable on film while being not so obvious when you were out in the bright sun, concentrating on other things. Yes, a lens board can leak light, but they usually don't. When they do it doesn't look like this.
-- Kevin Crisp (KRCrisp@aol.com), February 24, 2002.
You say white lines on your negatives,but this is a positive print with white lines?The lines on this picture do not resemble a light leak.Light leaks tend to spray unfocused light around,causing fog on the film,not sharply focused white lines in a print.The above test can be done with a smaller than 100 watt light bulb.Try a 40 watt bulb inside the camera in a completely dark room.Hold up a sheet of white paper all around the camera,and watch for light strikes on the paper.
-- edsel adams (email@example.com), February 24, 2002.
They are contrails. From the looks of them you live somewhere in the mountainous western states or some similar region. If I'm right there's a good chance they weren't in your ground glass frame when you were composing but drifted in before you took your shot.
Thats my 2 cents
-- Kevin (firstname.lastname@example.org), February 24, 2002.
What is peculiar is the direction of the streaks of light. In the beginning i thought it to be a leak in the back of your camera, then, as i said i noticed that the leaks have all the same angle which motivated me to hold responsible maibe the lens shutter? The streaks are quite sharp which could be given by the fact that the distance lens-film is short ( if you are using a WA) Could it be that some light reflects in one of the shutter blades ?Who will win this contest?
-- domenico foschi (email@example.com), February 24, 2002.
OK guys, cool your jets!, those are some pilots up there, they are in ALL my negs/pos. LOOK CLOSER, the white lines are all around the border of the print, just inside the black border. The contrails are exactly what they seem, I hope its the lesboard, it is starting to sound like it is coming from outer space! (not castille, spain)
-- adrian tyler (firstname.lastname@example.org), February 24, 2002.
What type of film holders are you using? Those white lines look like reflected light off of the inside edge of the opening in the film holder. This effect has been mentioned in other threads as being noticed with the new Kodak Single Sheet Readyload holder.
-- Glenn C. Kroeger (email@example.com), February 24, 2002.
Oh, now I see what you're talking about. Other than a little excess exposure from light reflecting off the edges of the film holder I have no idea. Maybe it's contrails from a pilot who is really, really precise.
-- Kevin Crisp (KRCrisp@aol.com), February 24, 2002.
Ok, Earlier I showed my prowess at pointing out contrails. Is there any chance that the white streaks at the border of the image have something to do with development? Maybe a negative frame that doesn't permit the chemistry to reach the emulsion where it gets clamped? Otherwise, good luck.
-- Kevin Kemner (firstname.lastname@example.org), February 25, 2002.
There's no way that a leak around the lensboard would form a thin white line around film at the back of the camera.
It looks as if you're using some fancy sort of filmholder to me, and not a standard double darkslide, judging from the pattern around the film. My guess is that your filmholder has a shiny metal edge that's reflecting light onto the film in a thin 'halo'. And since it's all of half a millimetre wide, and the film imprint cuts further into the frame, why worry about it?
-- Pete Andrews (email@example.com), February 25, 2002.
Those lines are from your holders, as others have pointed out. Take some emory cloth and sand the edges of the holders next to where the film goes. That will dull them down and should solve the problem.
-- Michael A. Smith (firstname.lastname@example.org), February 26, 2002.
Thanks very much to everyone, I'll sand down the fimback as Michael suggests and do some tests.
-- adrian tyler (email@example.com), February 27, 2002.