Black spots on 4x5 negative -- noob questions...

[timeUnit]

Ok, so I tried the tube developing method as presented by Sandy King here on APUG, and it worked out OK. The development looks very even to my eye. I should have been much more thorough when evening out the edges of the PVC tubes, because I got some ugly scratches on the negs. This will be fixed soon. Live and learn.

But, on two negs of four, I got BLACK spots. The spots are about 0.1 to 0.7 mm wide, and sharp. Looks almost like they're in the picture (a portrait of mum, window light). There are two or three of the big spots, and maybe 15 small ones. They seem to be placed randomly across the neg.

What can cause this?

I can think of:

1. Some kind of light leak. But the spots are sharp and small. Light leaks are most often like a fog on parts of the picture. Surely, pinholes in the bellows cannot be the culprit?

2. Defective film. It has happended before... Too many times, actually...

3. Something in the developer that reacts with the emulsion.


Some specs:

Camera: Cambo SC2, Rodenstock Sironar N 180 mm f/5.6, Lisco Regal Holders (bought used). The camera looks new, and the bellows seem unused.

Film: Fortepan 400. EI 320.

Developing: Rodinal 1+50 (25 ml developer, 1250 ml water), water stop bath, Ilford Hypam 1+4 fixer. Devtime 16 minutes, init. agitation 15 sec, then 10 sec every 5 minutes. Fixing 5 minutes, intermittent agitation. All at 20°C.

I did a search before this post, but to no avail.

Lots of thanks!

 

[Mike Kovacs]

Black spots on the print = dust on the film before it was exposed. You have to be super anal retentive about cleaning holders and loading in a low dust environment to avoid this problem.

Black spots on the neg, well that's another story.

 

[timeUnit]

Bump...

 

[argus]

OK to bump ;-)

Are the black spots created in the emulsion or are they sitting on the emulsion or film back side?
In the second case, the negatives are underwashed.

Could you post a scan?

G

 

[timeUnit]

They are in the emulsion, they look like exposed "stars" or highlights.

 

[timeUnit]

Will post a scan later. Maybe not tonight, but later.

 

[timeUnit]

I'll not put up any scans. There are too many variables. I need to do some testing. I'll shoot a new batch, and see how that goes. I got some ideas on what to try.