Massive light leak troubleshootingg

[Klainmeister]

Hi all, here's a fun one.

So I did the classic idiot mistake; I tried out new equipment on a trip. In this case, a recently acquired Standard 4x5 with some 3D printed lens boards. Why? I've been trying to shave some weight from the backpack and on this trip I am glad I did! Nevertheless, I developed a few BW sheets and didn't have any leaks, but my Ektar sheets are all...horrible. I'm trying to figure out if its the Fidelity Elite holders or something with the camera itself.

One theory I have is since I used Riteway holders with the BW and had no issues, maybe the Fidelity holders sit differently in the camera back and let light in (all color film was in the Fidelity holders).

Another is possible light leak from the lens boards itself? Granted, I should have gotten a leak from the BW images, I would think.

Please take a look at the attached and give me your opinion on where I should check next.

 

[shutterfinger]

Prints don't tell anything other than light leaked.
A picture of the negatives will tell us all we need to know.
With the lens board removed, bellows extended, suspect film holder installed, darkslide removed, in total darkness put a bright light into the bellows through the front standard and look for light escaping around the back.

 

[removedacct1]

Who made the 3-D printed lens boards? If not made correctly, they can leak light.

 

[jamesaz]

Don’t overlook the possibility of heat fog.

 

[removed account4]

if it is only a few sheets of film, maybe it is the film holders. if they are new/used to you sometimes people replace dark slides... and over the years darkslides have changed materials I know for a while there some of the toyo boards leaked light. perhaps people replaced leaky toyo dark slides with fidelity ones and sold off the fidelity film holders...
if you take paper and put them in your film holders and put them in the, sun process them you might be able to tell if they leak. pointing camera and 3d printed lens boards towards light and looking in through back of camera with lens closed will tell you if your lens boards are leaky .. some home fashioned ones forget about the light-dam...

 

[Donald Qualls]

3D printed lens boards are a likely source of the trouble -- few if any of the common PLA printing filaments are actually opaque at the thicknesses often chosen for lens boards; that means you're getting potential fogging any time the dark slide is out.

It is possible for 3D printed parts to be fully opaque -- with common filament, the solution is to make the lens board thick instead of the thin shell of the one 3D printed one I've bought. Alternatively, there are "more opaque" material choices (typically at higher material cost, so those selling boards, especially if they're not LF photographers themselves, are likely to choose the lower cost material). However, this is a good first place to look.

Since you already have this one, something you might try is covering the front side of the lens board with aluminum tape. Fully opaque, easy to apply, and possible to remove if needed.

 

[grat]

I know 3d printing is often pointed at as a scapegoat, but why would a 3d printed lensboard only pass light through when using color, and not B&W film?

Standard black PETG is more than capable of producing an opaque lens board at normal thickness, even with hollow infill. There are also opaque PLA filaments, but you have to look for them.

I test mine with several thousand lumens at point blank range.

 

[Donald Qualls]

why would a 3d printed lensboard only pass light through when using color, and not B&W film?

Very unlikely to be the case, but the resulting fogging would be more noticeable because the human visual system notices color overlays much more than overall fog (which would usually be printed or scanned through anyway).

 

[Klainmeister]

Hmmm interesting.

The strange part is the color negs look visually normal when not inverted, so you may be right. I'll do some testing on the boards and the holders and see.

 

[grat]

Very unlikely to be the case, but the resulting fogging would be more noticeable because the human visual system notices color overlays much more than overall fog (which would usually be printed or scanned through anyway).

That's fair. And I'm not actually saying it *isn't* the lens board-- stranger things have happened. Definitely worth shining a very bright light at the board from close range.

Looking more closely (I was on my phone last time), I noticed the second picture has what appears to be a "classic" film holder light leak in the top left (so bottom right with film holder loaded).

There also seems to be some areas that aren't fogged on the left and right edges, especially on the second image, where the unfogged region has a definite circular shape to it.

 

[abruzzi]

also, on that second picture, on the lower right, the "red flare" ends before the picture ends. When I see that it makes me think the last half inch that isn't affected by the red, was in a shadow (i.e. something blocked the light leak from affecting that last bit of the image.) For that to happen, I would usually expect the light leak to be close to the back of the camera. Something towards the front, and especially a translucent lens board, wouldn't be blocked but a tear towards the rear of the bellows, or a quick release bellows that was not properly refitted might let some light in close enough the hardware on the rear standard, that the bit in the corner was in the light leaks shadow.

None of that explins why the B&W images weren't affected.