A challenge to the finest minds in LF: The ghost imagegreenspun.com : LUSENET : Large format photography : One Thread
Here is a problem that really has me stumped! My hat's off to whoever can figure this one out.
I recently acquired some Sinar adhesive 8 X 10 holders. Though not new, they are from a reputable source. Whatever image I shoot with these, all four shots in 2 holders come out with a very obvious branching or arborizing pattern. This is not subtle! It looks as if I had made a double exposure with a forest shot, though I definiely did not. Shots made interspersed with other holders have no such ghost images. Though similar, the placement of the images is different on shots from each holder. Is this:
1. A chemical reaction of the adhesive to the film? Perhaps the original adhesive degraded over time, or was replaced? (But close up, these really look like TREES, more than a chemical fractile-like pattern).
2. Emulsion from someone's old shot where the film was inadvertently loaded with the emulsion facing the adhesive (Could explain the similarity of patterns from the different holders: a full day of shooting in the forest with film loaded backwards in all the holders?)
I have to admit these sound pretty far-fetched! But I have no doubts at all about what I'm seeing. I suppose I could keep shooting and see if the problem slowly goes away, but I'm not keen to waste that much HP5+! I will contact Sinar and the seller, but I thought that some of the resident Great Thinkers on this forum were my best bet. I would be very grateful for an explanation, and a practical solution would be True Nirvana!
Thanks in advance,
-- Nathan Congdon (firstname.lastname@example.org), December 20, 2000
Addendum: For whatever it's worth, these are all HP5+ negs tray- processed identically in PMK pyro (80 degrees, 8 min), one sheet per 11 X 14 tray.
-- Nathan Congdon (email@example.com), December 20, 2000.
Just to check, have you made more than one exposure with each side of each holder? If so, do the patterns match from negative to negative - i.e. two negs from the same side of the same holder held together on the light box?
Could it be that the adhesive is getting old and has lost some of it's tack? Or rather - retained tack on the film side but lost it on the holder side? Then residual adhesive on the film is lost during developement?
If not, then it could be part of your loading procedure - uneven contact with the adhesive? What about your shooting conditions - are you loading indoors and then shooting outdoors? Could it be condensation between the holder and the negative?
If the emulsion from someone's previous negative was left on the holder platten - wouldn't you see it?
-- Sean yates (firstname.lastname@example.org), December 21, 2000.
? Electrical discharge?
-- Hans Berkhout (email@example.com), December 21, 2000.
Very mind-boggling! I would second the idea of a static electricity problem. When loading and unloading the films, try to make everything very slowly to avoid the static discharges...? I have noticed the small "lightenings" too when loading/unloading 4x5 holders too quickly. The large size negatives can only encrease the risks. If the air is very dry, the problem can be quite bad although I had never noticed anything on my low sensibility color slides. The arborescences should be darker (exposed) on your negatives.
-- Paul Schilliger (firstname.lastname@example.org), December 21, 2000.
Is it a chemical reaction with/coating of the anti-halation backing of the film that you are using prventing the clearing og the backing? If not I vote for static marks.
-- Wayne DeWitt (email@example.com), December 21, 2000.
I'll bet it is 'triboluminescence', light produced by quite a few polymers and inorganic materials when rapidly stressed. 'Wintergreens' are supposedly a US candy which does this when bitten into, and the adhesive at the end of most 120 roll films will also show the effect if you tear the backing paper from the film fast enough.
I can't believe that Sinar would be daft enough to use an adhesive which luminesces enough to fog film. Perhaps your source has renewed the tackyness with an unsuitable adhesive?
-- Struan Gray (firstname.lastname@example.org), December 21, 2000.
Nathan: When some adhesive tapes are released from the substrate in the dark, light can be seen to be released. I always thought this was caused by static electricity; friction or energy between static prone materials always causes static electricity that can cause such sparks. Struan indicates 'tryboluminescence', he probably is right, I was not aware of that phenomenon. Of course, Sinar should have tested the adhesive and of course, this did not happen at Halloween?
-- Julio Fernandez (email@example.com), December 21, 2000.
I had a similar experience in the darkroom whilst ripping the tear-off strip from a new pack of Ilford multigrade paper, a large firework display of green light from the glue! whilst trying to replicate the dispaly recently nothing happened so Ilford must have caught on.
-- dave bulmer (firstname.lastname@example.org), December 21, 2000.
Nathan: I really shouldn't be answering your question since you wanted an answer from the finest minds in LF. I certainly don't fit in that catagory. However, I would go along with the static electricity theory. It wouldn't take much of a discharge with the film in contact with the adhesive. It is possible that the adhesive has been renewed with one that produces a current when the film is removed. Since the pattern appears to be tree branches, that pretty well confirms the theory of static charge. I suspect it occurs when you remove the film from the holder.
-- Doug Paramore (email@example.com), December 21, 2000.
Quick! Before you return the film holders you should simply insert the film as though you are going to take a picture, take it out for proccesing without having exposed it, and print the resulting image. Do it for fun; it might be interesting.
-- Luke Nasaw (firstname.lastname@example.org), December 21, 2000.
It might also be fun to open and close the darkslide in a darken room, and remove the film while watching for the static discharge or triboluminescence. I learned a long time ago to cut rollfilm instead of messing with the tape.
-- Wayne DeWitt (email@example.com), December 21, 2000.
Up here in the north, cold dry days create all kinds if interesting problems, usually at inconvenient times...
-- Steve Clark (firstname.lastname@example.org), December 21, 2000.
Nathan: See Clark's posting, he adds a very important bit of information that I ommitted in mine: HUMIDITY, or to be precise, the lack of it. When relative humidity drops below 50%, static build up can be a real problem. In heated buildings in cold weather, I have seen humidity drop to as low as 15%. When you load film, particularly over some static-prone carpets, and particularly if you are wearing rubber soled shoes, it is best to have handy a 'static drain' in the form of a copper cable connected to the ground terminal of one of your light sockets. Some electric plugs are available that have attached an exterior short wire connected to the ground terminal so that you can connect to it. Before handling film you touch the cable with your bare hand to drain the static. This of course may not help you with static caused during the peeling of adhesive tape, however it may save you from other problems from static sparks. In dry air, static can be a hidden enemy also in the handling of flammable substances, beware!
-- Julio Fernandez (email@example.com), December 22, 2000.
Be *very* careful about directly grounding yourself to an electrical outlet. They've been miswired once or twice. I suggest that, even if you want to trust the "ground" opening on an outlet as actually being at ground potential, you place a 1 megohm resistor in circuit between you and the outlet. Hold on to your wire for a couple of seconds; the static will drain off in that period, and you'll be safe just in case.
-- Sal Santamaura (firstname.lastname@example.org), December 22, 2000.
You can buy a static-discharge wrist strap for under $10 at just about any electronics parts store. Many computer shops which sell tools will have them, too.
-- Brian C. Miller (email@example.com), December 23, 2000.
So, do we have a verdict yet?
-- Sean yates (firstname.lastname@example.org), January 17, 2001.