Should filmholders be light tight with darkslide removed?

claytume · Mar 13, 2005

I have some new custom holders, very nicely made, no complaints there. In the first test shots with them the film was heavily fogged so I thought I better do some testing for light leaks. Everything was fine apart from shooting with the darkslides sompletely removed so the light traps in there aren't sealing well.

The sun at the time was directly overhead and not shining straight into the darkslide opening. I tried some shots with the opening protected with the dark cloth and also with the darkslide partially inserted, both were fine as you'd expect them to be.

I've never come across this problem with Fidelity, Lisco, Graflex etc holders, all seem to perform ok with the darkslide out as long as the sun isn't directly shining on the opening.

The problem with leaving the darkslide partially in or a darkcloth over the camera is it isn't always convenient, especially with some wind around.

Clayton

dancqu · Mar 13, 2005

claytume said:
I have some new custom holders, very nicely made, no complaints there.
In the first test shots with them the film was heavily fogged ...

Unevenly fogged I'd think. The maker of the holders may not
have knowen of the felts which need to be installed. Dan

Jorge · Mar 13, 2005

claytume said:
I have some new custom holders, very nicely made, no complaints there. In the first test shots with them the film was heavily fogged so I thought I better do some testing for light leaks. Everything was fine apart from shooting with the darkslides sompletely removed so the light traps in there aren't sealing well.

The sun at the time was directly overhead and not shining straight into the darkslide opening. I tried some shots with the opening protected with the dark cloth and also with the darkslide partially inserted, both were fine as you'd expect them to be.

I've never come across this problem with Fidelity, Lisco, Graflex etc holders, all seem to perform ok with the darkslide out as long as the sun isn't directly shining on the opening.

The problem with leaving the darkslide partially in or a darkcloth over the camera is it isn't always convenient, especially with some wind around.

Clayton

Yes, the holders should be light tight with the slide removed. Send them back and make them do it right.....BTW IMO they should pay for shipping both ways...

claytume · Mar 13, 2005

Thanks for the replys.

I decided some more testing was required to get to the bottom of it. I tested all the new custom holders, all leak light in the same way and show exposure at the open end of the holder, the end the darkslide enters/exits. This is with the camera turned away from the sun, 1 minute exposure onto B&W paper.

Next I tested an 8x10 Graflex holder which is in good condition and at least 40 years old.

First test 1 minute photo paper, opening away from sun......result perfect, no exposure.

Next test 1 minute photo paper, opening toward sun......no exposure.

Next, 5 minutes paper, opening toward sun.......no exposure.

Last test, 30 minutes paper, opening toward sun.......no exposure.

So from my tests on an old film holder it appears external light sources should have no bearing on light tightness of a holder.

Anyone else want to comment or had problems with custom holders.

Clayton

David A. Goldfarb · Mar 13, 2005

Sounds like an obvious problem with the light trap. If the holders are new, you shouldn't be having this problem.

All the manufacturers of custom filmholders seem like pretty honorable folk. Whoever it is should make it right.

BarrieB · Mar 13, 2005

Greetings, YES Dark Slides Must and Should be LIGHT-TIGHT, However, with the opening directly facing the sun for many seconds the may be a problem: Even 35mm cassettes should be loaded into the Camera in the shade of your body.

ras351 · Mar 13, 2005

It might be worth sticking a small torch inside the camera and taking it into the darkroom to see if you can spot the leak. With the lens shutter closed and the darkslide removed you shouldn't be able to see any stray light coming from the camera. I had to do a similar test a year or so ago with a new holder but it turned out to be the processing drum which was leaking. It's also a useful way to find pinholes in bellows.

Roger.

claytume · Mar 13, 2005

ras351 said:
It might be worth sticking a small torch inside the camera and taking it into the darkroom to see if you can spot the leak. With the lens shutter closed and the darkslide removed you shouldn't be able to see any stray light coming from the camera.

Roger.

I tried this and you can definitely see the leak, takes a bit to get your line of sight in the right place but when you get it the leak is the full height of the slide.

The light trap appears to be working ok on all the holders so they either need more tension or a deeper rebate to seat in.

Clayton

sanking · Mar 13, 2005

claytume said:
I tried this and you can definitely see the leak, takes a bit to get your line of sight in the right place but when you get it the leak is the full height of the slide.

The light trap appears to be working ok on all the holders so they either need more tension or a deeper rebate to seat in.

Clayton

Check to verify that the light leak is actually coming through the baffle, and not between the holder and the camera back. If the holder does not fit correctly into the camera, i.e. if the rib lock does not drop into place in the groove on the camera back, there will be a very gross light leak, and it will happen with every single holder, as you describe. Most people are not aware of this but there are not any size standards, such as ANSI, for the banquet and panorama cameras, and a very high percentage of problems with light leaks are caused not by the holders but by the way they fit the camera.

I suspect that the probem may be the fit of the holder in the camera, and not the holders themself, because of the location of the fogging. Normally if the light comes through the baffle it does so at such an angle that it fogs the film at the other end of the holder, i.e. the flap end, not at the end near where the slide is inserted. It is very unusual, and would take a case of a rather gross lack of light integrity of the light baffle for the light to actually fog the film at the baffle end because its angle of entry does not normally allow it to reach the film at that point..

Sandy

claytume · Mar 14, 2005

Update

sanking said:
Check to verify that the light leak is actually coming through the baffle, and not between the holder and the camera back. If the holder does not fit correctly into the camera, i.e. if the rib lock does not drop into place in the groove on the camera back, there will be a very gross light leak, and it will happen with every single holder, as you describe. Most people are not aware of this but there are not any size standards, such as ANSI, for the banquet and panorama cameras, and a very high percentage of problems with light leaks are caused not by the holders but by the way they fit the camera.

I suspect that the probem may be the fit of the holder in the camera, and not the holders themself, because of the location of the fogging. Normally if the light comes through the baffle it does so at such an angle that it fogs the film at the other end of the holder, i.e. the flap end, not at the end near where the slide is inserted. It is very unusual, and would take a case of a rather gross lack of light integrity of the light baffle for the light to actually fog the film at the baffle end because its angle of entry does not normally allow it to reach the film at that point..

Sandy

Sandy has the answer here and a good lesson for the odd size cameras out there.

I checked the rib lock seating and it appears my camera has a design fault in this area. The groove the rib lock seats in isn't a groove at all but a simple step. I checked this groove on all my other cameras and they do indeed have it. Something I was never aware before as I've never had a light leak problem around the back.

I did a quick temporary repair and added the missing side to the groove. This time the test was fine, full afternoon sun onto the holder with slide removed. After a few minutes I put the slide back in, processed the paper and not a mark on it.

thanks to everyone that replied

Clayton

Jim Chinn · Mar 14, 2005

Some older cameras also have the rib as part of the camera back, which requires the film holder to have a groove instead of the rib. When you say it had a simple "step", could that step mate to a corresponding slot or groove on the original holders?

The only reason I mention this is if you add a piece to create a groove for your holders you may move the rear of the holder away from the back of the frame. Check for any light leaks back there.

The interesting thing about this thread is that Jim from Midwest Photo bought a 12x20 camera at the local camera show (I think it was a korona) and the film holders had a groove in them not a rib. So of course they will not work with the camera (which also has a groove) with out some modifications.

I am curious as to which cameras makers made ULF cameras that used the goove on the holder and the rib on the camera?

David A. Goldfarb · Mar 14, 2005

Not ULF, but just for the record, Graflex-type holders work this way. There is a metal rib on the camera back and a square-cut groove on the filmholder. There are also grooves on the sides for Graflok-style slides, but these aren't part of the light trap (the holders also work with Graflex-sized spring backs).

sanking · Mar 14, 2005

Jim Chinn said:
The interesting thing about this thread is that Jim from Midwest Photo bought a 12x20 camera at the local camera show (I think it was a korona) and the film holders had a groove in them not a rib. So of course they will not work with the camera (which also has a groove) with out some modifications.

I am curious as to which cameras makers made ULF cameras that used the goove on the holder and the rib on the camera?

Speaking only of banquet and panorama cameras of the past, so far as I know only Folmer & Schwing had a system which had the groove on the holder and the raised rib lock on the camera back.

Since the Korona style system (rib lock on holder, groove in camera back) is by far the more common, and the only one used today for banquet camera holders, I generally recommend that people who own F&S cameras and need more film holders remove the raised rib on the back and rout a groove there to accept Korona style holders. This could easily be done with a dremel type tool by someone with little or no skill in wood working, assuming they understand the basic premise of what needs to be done.

Sandy

sanking · Mar 14, 2005

claytume said:
I checked the rib lock seating and it appears my camera has a design fault in this area. The groove the rib lock seats in isn't a groove at all but a simple step. I checked this groove on all my other cameras and they do indeed have it. Something I was never aware before as I've never had a light leak problem around the back.

Clayton

I can not see clearly in my mind the kind of system your camera has, but it would appear to me that if there is only a stop, and not a groove, then the rib lock on the holder would hold it slighly away from the back, which could screw up focus even if you have light integrity. For that reason I would definitely suggest that you rout a groove into the camera back to accept the rib lock of the holder so that the holder lies flat in the back.

If there is any slop in the fit of the holder in the back I would further recommend that you glue spacer strips at the top, bottom and far side if necessary, to reduce the amount of slop since extra space at the top and bottom and/or the sides is also a potential cause of light leaks. And you might want to do this with the ground glass removed so that you can check the impact of any changes on the positon of the ground glass, which is where yoiu see the image when you focus and compose, in relation to the opening in the film holder, which is where the image is actually made.

Sandy

claytume · Mar 14, 2005

sanking said:
I can not see clearly in my mind the kind of system your camera has, but it would appear to me that if there is only a stop, and not a groove, then the rib lock on the holder would hold it slighly away from the back, which could screw up focus even if you have light integrity. For that reason I would definitely suggest that you rout a groove into the camera back to accept the rib lock of the holder so that the holder lies flat in the back.

Sandy

Here's a photo that explains it better. As it was difficult to show the step in the photo I've drawn a red line that follows the shape of the woodwork. The holder rib is supposed to be pulled against this step, clearly it doesn't work and some light leaks through. I have an easy solution of adding a plastic strip down the open side which will form a groove for the holder rib to sit it.

Incidently this is a new camera.

Clayton

claytume · Mar 14, 2005

Here's another shot, back removed from camera, holder inserted, view from lens side of camera back.

Notice the holder rib can be seen, clearly this is wrong and leads to the light leak I've experienced. The rib should be enclosed in a groove.

Clayton

sanking · Mar 14, 2005

claytume said:
Here's another shot, back removed from camera, holder inserted, view from lens side of camera back.

Notice the holder rib can be seen, clearly this is wrong and leads to the light leak I've experienced. The rib should be enclosed in a groove.

Clayton

Yes, that design definitely looks suspect to me. In principle one might speculate that the design would work just as well as a complete groove, but in practice what I suspect happens is that it allows reflected light to get under the rib lock, and then since there is no barrier it makes itself directly to film.

When you adjust the groove you should also make sure that, 1) it is just slightly deeper than the depth of the rib lock on the holder, and 2) that the holder lies perfectly flat on the forward surface of the back.

However, when actually working in the field I make it a point to never, never completely trust the light integrity of wooden cameras and holders so I always cover the area around the baffle with a dark cloth when the slide is removed, and to the extent possible, while removing and inserting it.

Sandy

claytume · Mar 19, 2005

Update

sanking said:
Yes, that design definitely looks suspect to me. In principle one might speculate that the design would work just as well as a complete groove, but in practice what I suspect happens is that it allows reflected light to get under the rib lock, and then since there is no barrier it makes itself directly to film.

Sandy

I did a simple modification on the camera back by closing off the open side of the groove the holder rib sits in with a strip of black plastic.

Testing with film shows no evidence of light leaking through.

Thanks to all that contributed to this thread.

Clayton

Should filmholders be light tight with darkslide removed?

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