Black spots on 4x5 negatives: darkslide light leaks?

[wiltw]

Hi! I am a beginner with large format (4x5). I have those black spots on a couple of negatives (white on prints and scans). Mostly on one negative and a little bit on a second one. They seem to appear in the same general area in both cases.

Black on negative, white on print...I totally disagree with speculation about DUST!
Light causes the silver particles in the film emulsion black, that is why 'no light' results in CLEAR margins of the film excep for the pre-exposed film type already flashed into the film during manufacture. Black on negative then shows up on prints as a very 'bright' area or WHITE on the print!

I can propose that you pull out dark slides from film holders, and hold it up to a bright source of light like a fluorescent panel, so you can perhaps see where little pinholes exist...better yet, simply throw out the dark slides and holders and buy new ones!

IF it were indeed dust on the negative, that shows up as a clear area because it blocked light from striking the emulsion and not darkening the silver particles...and white on the negative shows up black on the print -- where NO LIGHT strukes the film it is dark on the print.

 

[Donald Qualls]

Very unlikely that a modern dark slide could develop pinholes in that kind of quantity -- and if it did, it would have produced much wider spots than those (pinhole camera with 3mm focal length -- images would be overlapped and blurred out, but the spots would be at least as wide as the space between dark slide and film). If the dark slide was metal and very badly rusted, I might believe it.

With the price of film holders these days, it's irresponsible to just trash one without being sure it's at fault. At least a paper test in direct sun seems like a cheap way to eliminate the film holder as the source.

 

[Photopathe]

The brand is Fidelity elite and they seem to be in very good shape. As i said, i already tested the dark slides With a strong flashlight.

 

[Donald Qualls]

Those have a plastic dark slide, do they not? Definitely not prone to pinholes, but potentially to static build-up.

 

[DWThomas]

Particularly the shapes in the second shot make me wonder if there was mold on the film or contact with a chemical spatter -- perhaps some dry chemical powder. I won't even try to guess what such foreign material might be or how it got there.

 

[Kilgallb]

On the print, or on the negative?

On the print.

 

[drpsilver]

31 Aug 2020

Photopathe:

I agree that pre-exposure dust would look like clear spots on the negative (dark spots on the print). How long, and under what conditions, was this film stored in the holder before being processed? I could imagine condensation on the film before processing. If these black spots are a result of pinhole light leaks they should show-up on every negative, unless the pinholes need to directly lit in order to be "seen".

Regards,
Darwin

 

[Photopathe]

They were stored in the film holder placed in the fridge for a few weeks at some point but were taken out of the fridge at least a few hours before use. Maybe a couple of hours, maybe a couple of days I don't recall in this case. Condensation could cause these spots if condensation was present during exposure, is that correct?

 

[Donald Qualls]

Condensation could cause spots and possbily runs even if it has evaporated by time of exposure, by moving sensitizing dyes around in the emulsion. Droplets of water on the emulsion surface at exposure could act as lenses, producing dark (in the negative) spots with light rings around them.

Any film of mine that goes in the freezer gets airtight packaging (zipper bags, or its own foil pouches), and I don't refrigerate film -- it's either freezer or room temp. The last few months I've been shooting Fuji color film and Fomapan that was at room temperature for up to fifteen years, and it's been fine -- but the 1990s vintage Vericolor (unperfed 35mm, intended to make up 828 rolls) is in the freezer until I'm ready to start using it.