Lightleak or development issue?

[RichardRitter]

Holder may not be in the lock grove.
Or when you put the dark slide back in you put it between the holder and the back.
Or as Doremus said You put the holder way from the back when you pull it out.

The light path of your problem is coming from the end with the lock rib.

[Jerry Bodine]

...The design of the flap has baffles that make it light-tight when closed unless the flap itself is damaged or warped...

Doremus, I have a lot of respect for your views on many topics, but I have some thoughts on the topic at hand that I’d like to run by you. The design of the flap is intended to prevent light from striking the film when the light source is the lens, but when the aforementioned gap allows light to come from the end opposite the flap, the light approaches the flap nearly parallel to the film plane, then encounters the flap baffles. There is no soft material under the flap to create a really good seal (like the felt trap at the opposite end of the holder), the flap baffle is instead a matter of hard surface-to-hard surface (not a perfect seal in this scenario). So I envision very low intensity light from the far end of the holder getting through this interface (think VERY small aperture) and reaching the film to expose the rebate. In fact when I examined one of my Fidelity Deluxe holders, I noticed a definite opening (by design) nearly ¼” wide at each end of the flap’s “baffle” where the low-angle light can pour through to the rebate. Obviously, the solution is to prevent the gap in the first place, using good technique as mentioned above. Comments?

[RichardRitter]

Steve Grimes when he was a member of this forum stated the best way to prevent problems of light leaks was to keep the focusing cloth over the bellows and back of the camera. Photographers learned this 150 years ago.

[howlingsun]

Steve Grimes when he was a member of this forum stated the best way to prevent problems of light leaks was to keep the focusing cloth over the bellows and back of the camera. Photographers learned this 150 years ago.

Never to late to learn I hope. Taking this to heart.

[MusicalPhotog]

Since the rebate of the film is exposed, I believe that the light strike is happening when the film is out of the holder. The rebate rails cover the film and hide it from light strikes in-camera (or exposing the film normally would expose the rebate too...). I'd have a look at your development tank for cracks, missing seals, whatever that might cause a light leak. Also check your film-loading/unloading environment (darkroom/changing bag) for stray light and leaks.

Yes, pulling the back away from the camera body when pulling/inserting the darkslide is a common cause of light strikes, but the exposed rebate tends to rule that out in this case. (Do pinch back and camera body together with your free hand when pulling and inserting the darkslide, however!)

Lastly, check your holders for cracks along the side seams. I had a few that leaked that way; letting light in right at the side of the film. Toyo holders are pretty well-built, however.

By the way, the flap on film holders will not leak light as long as it is closed and the darkslide inserted. The condition of the tape is irrelevant; it is only there as a hinge. The design of the flap has baffles that make it light-tight when closed unless the flap itself is damaged or warped. The myth that faulty or missing hinge tape causes light leaks is rather prevalent here, but false.

Best,

Doremus

I tend to agree more with this assessment. Because the rebate edge is involved--but only slightly, thereby casting a minor 'shadow' of fog across the edge and notch codes--I am inclined to suggest looking at your loading and/or development conditions. If the leak was in the film holder itself, then it would presumably receive a certain amount of light for a longer length of time, which would cause a denser fog proportionate to the amount of time exposed. (The longer film is in a holder, the denser the fog.)

You may also have a bad box of film. Exposing film to adverse environmental conditions can cause a fog-like condition.

[Colin Graham]

Doremus, I have a lot of respect for your views on many topics, but I have some thoughts on the topic at hand that I’d like to run by you. The design of the flap is intended to prevent light from striking the film when the light source is the lens, but when the aforementioned gap allows light to come from the end opposite the flap, the light approaches the flap nearly parallel to the film plane, then encounters the flap baffles. There is no soft material under the flap to create a really good seal (like the felt trap at the opposite end of the holder), the flap baffle is instead a matter of hard surface-to-hard surface (not a perfect seal in this scenario). So I envision very low intensity light from the far end of the holder getting through this interface (think VERY small aperture) and reaching the film to expose the rebate. In fact when I examined one of my Fidelity Deluxe holders, I noticed a definite opening (by design) nearly ¼” wide at each end of the flap’s “baffle” where the low-angle light can pour through to the rebate. Obviously, the solution is to prevent the gap in the first place, using good technique as mentioned above. Comments?

The felt and springs are there on the darkslide end because it's a straight light path. On the flap end, most holders have a stepped rabbet or dado on the flap that interlock with a mating piece on the end of the septum to break the light path. The flap is also usually wider that the film septum, with recesses notched into the side rails for the flap ends. If the tolerances are good and the internal surfaces are black, then there should be no reflections that spill light onto the film plane, no matter which direction the light is coming from.

All that said, I have some 5x7 Fidelity holders with loading flaps that are slightly undersized in width (5 thou or so short of the mating notch in the side rails), and each corner of developed film on the loading end always has a tiny black hash mark in the rebate from a light leak. It's very sharply defined though and doesn't fog the image area.

[Doremus Scudder]

Doremus, I have a lot of respect for your views on many topics, but I have some thoughts on the topic at hand that I’d like to run by you. The design of the flap is intended to prevent light from striking the film when the light source is the lens, but when the aforementioned gap allows light to come from the end opposite the flap, the light approaches the flap nearly parallel to the film plane, then encounters the flap baffles. There is no soft material under the flap to create a really good seal (like the felt trap at the opposite end of the holder), the flap baffle is instead a matter of hard surface-to-hard surface (not a perfect seal in this scenario). So I envision very low intensity light from the far end of the holder getting through this interface (think VERY small aperture) and reaching the film to expose the rebate. In fact when I examined one of my Fidelity Deluxe holders, I noticed a definite opening (by design) nearly ¼” wide at each end of the flap’s “baffle” where the low-angle light can pour through to the rebate. Obviously, the solution is to prevent the gap in the first place, using good technique as mentioned above. Comments?

The felt and springs are there on the darkslide end because it's a straight light path. On the flap end, most holders have a stepped rabbet or dado on the flap that interlock with a mating piece on the end of the septum to break the light path. The flap is also usually wider that the film septum, with recesses notched into the side rails for the flap ends. If the tolerances are good and the internal surfaces are black, then there should be no reflections that spill light onto the film plane, no matter which direction the light is coming from.

All that said, I have some 5x7 Fidelity holders with loading flaps that are slightly undersized in width (5 thou or so short of the mating notch in the side rails), and each corner of developed film on the loading end always has a tiny black hash mark in the rebate from a light leak. It's very sharply defined though and doesn't fog the image area.

Colin has explained the function of the flap superbly. If everything is correctly designed and in good working order, no light should pass the flap. The small light leaks in the very corners of some holders are due to a bit of play in the tolerances and usually don't impinge on the image area.

The main point I'm trying to make is that replacing the hinge tape on your holder's flap is not going to fix light-leak problems. Maybe judicious taping would eliminate the "hash marks" in the very corners that Colin describes, but certainly not the OP's problem.

Best,

Doremus

[Jerry Bodine]

Thanks for the enlightenment, guys.

[howlingsun]

Update
I made 2 identical exposures today. I changed the following:

1. I kept a dark cloth over the camera when the darkslide was removed and I took greater care when removing and putting the darkslide back.
2. I took much greater care with the development tank and kept the rubber lid on more. I also turned the lights off when doing the development although there was still light from a window, but much less.
3. I turned one of the negatives upside down in the tank this time, meaning the cutouts towards the bottom of the tank. This way I should be able to see if it is a holder or development issue.

The negatives are drying now so a bit early to tell, but I do not see the uneven border any more. I will see tomorrow how they look.