what light source to use in B&W reversal re-exposure

spoolman · Dec 8, 2015

I'll be starting tests soon on B&W film reversal processing. Would there be any difference between incandescent light bulbs or Compact Florescent lights as the reversal exposure light source?.

Doug

mnemosyne · Dec 8, 2015

I don't think there is a big difference and I cannot see a problem as long as the CFL can stay in its lamp housing and is not moved during exposure. I would not want to put CFL in any situation or surrounding where there is a certain risk of physical damage to the lamp. You don't want to have your darkroom contaminated with mercury because you accidentally dropped or smashed the lamp against something while handling it.

Most CFLs are not ideal for darkroom applications, as they can have considerable afterglow and/or need a couple of seconds to come to full brightness. In a darkroom you switch off and on your "master light" a lot, and what you want is instant darkness and instant brightness, and what you not want is to always have to wait 10 or 15 seconds for the lighting to catch up. I know there are better CFLs that overcome these problems, but given the price of LED bulbs nowadays I would simply go for one of those or stay with incandescent light.

Gerald C Koch · Dec 8, 2015

No difference.

mts · Dec 9, 2015

I use an outdoor flood lamp in an outdoor water-resistant fixture above the sink. The outdoor floodlamps are made from heavy glass and designed to be weather (water) resistant.

Steve Roberts · Dec 9, 2015

I use a 100W incandescent lamp. The film stays in its translucent reel immersed in water about a foot away from the lamp and I turn it constantly for three minutes one way up, then three minutes the other way up. That time doesn't seem too critical, but too much rather than too little seems to be the better option.

Steve

Truzi · Dec 9, 2015

Not to get off-track, but can a reversal exposure work with steel reels?

destroya · Dec 9, 2015

I use a chemical reversal process. It also fixes the film. Much easier and faster.

davedm · Dec 10, 2015

I also use a chemical reversal with stannous chloride.

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pdeeh · Dec 10, 2015

Truzi said:
Not to get off-track, but can a reversal exposure work with steel reels?

I expect it can, but the extra difficulty over (translucent) plastic reels is that the metal is opaque, and if you are not careful they might cast shadows which might mean you end up with uneven re-exposure.

Even using plastic reels, I try to keep them moving in front of the light source in all planes in such a way that this won't happen.

"It's all in the wrist action!"

Ian Grant · Dec 10, 2015

You have to avoid gross over-exposure and light that has a high blue or UV content which is why a tungsten light bulb is usually recommended.

Ian

avortex · Dec 10, 2015

I also use a chemical reversal with stannous chloride.

Would you mind to share your formula? It would be quite interesting...

fdonadio · Dec 10, 2015

avortex said:
Would you mind to share your formula? It would be quite interesting...

+1

destroya · Dec 10, 2015

I use Iron out, a rust remover. its primary ingredient is sodium hydrosulfite aka sodium dithionite. I use 1 teaspoon for every 200 ml of water in my tank. easy, yes, but it does smell funny. You must use distilled water as the Iron out will react to tap water! this is 1 shot, so use and dump.

Gerald C Koch · Dec 11, 2015

Truzi said:
Not to get off-track, but can a reversal exposure work with steel reels?

YES During exposure wobble the reel about to allow the light to reach all portions of the film. I have used this method extensively with color reversal film.

For those using chemical fogging be sure that the reel and tank are thoroughly washed.

davedm · Dec 12, 2015

avortex said:
Would you mind to share your formula? It would be quite interesting...

The method was actually developed by Jens Osbahr (pdf : Dead Link Removed), a former regular member of this forum. A must read for anyone attempting B&W reversal along with Ilford's guide.

The method uses SnCl2 (actually - stannous chloride dihydrate) mixed with second developer. However, for all practical purposes, It could be used as a separate bath with 0.05 to 0.1 g per 260 ml (~0.2 to 0.4 g/lit).

Please keep in mind that the solution is not stable and must be prepared fresh every time. Hence an inexpensive but accurate scale is required (http://goo.gl/DswQcd Or http://goo.gl/m49KtS).

P.S. Although the range is specified in the original document, you can try using a single value for all the film if you use this as a separate bath.
P.P.S. color slide film process E-6 also uses SnCl2 as reversal agent.

Tom Taylor · Dec 12, 2015

For re-exposure I've been using a small Photoflex soft box with a 500 watt bulb at a distance of 3-4 feet, 1 minute per side. After reading abojut the supposed difficulty of re-threading wet film onto plastic reels,I bought Hewes 35 and 120 SS Jobo reels but decided not to use them because the sulfuric acid would eventually eat away the reels soldering points. It turned out there is no difficulty in re-loading wet film onto Jobo 120 reels.

I did my initial tests with Kodak TMax 100 following the David Wood recipe in the Darkroom Cookbook and posted the results here: (there was a url link here which no longer exists)

Thomas

fdonadio · Dec 12, 2015

davedm said:
The method was actually developed by Jens Osbahr (pdf : Dead Link Removed), a former regular member of this forum. A must read for anyone attempting B&W reversal along with Ilford's guide.

Thank you, Dave!

what light source to use in B&W reversal re-exposure

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