Paper neg...positive...?

[Randy]

I don't know where to ask this question but I have read that some people process B&W film converting it to a positive rather than a negative. Am I correct? If so, can you not do the same with B&W silver gelatin paper, shoot it in camera as some do, but develop it in a way to convert it to a positive, rather than having to scan it, or contact print it to convert to a positive? I know that positive paper has been manufactured, but I was wondering if anyone has converted negative paper to a positive, chemically.

[jnantz]

hi randy

on apug there is someone doing that
search for B&W Reversal Process ( I think thet is the title )

it involves
exposure
development,
bleaching,
clearing,
exposing to light again and
redevelopment /fix ...

I believe freestyle is selling single step direct positive paper again ..
seems to be similar with out the exotic process ( just dev stop fix )

good luck!

[Randy]

I just found someone had posted a recipe on the forum (http://www.largeformatphotography.info/forum/showthread.php?112637-Paper-Negative-Reversal-Process-(In-camera-positives)) for doing just what I was asking - interesting. He also has a flicker post (http://www.flickr.com/groups/1011045@N21/discuss/72157642870149194/) covering his experiment.

[jnantz]

:) its the same guy
good luck with the fun !
john

[stiganas]

Film is expensive, paper is expensive so I decided to do paper positives if I am going to play with paper.

I read a couple of recipes from APUG and various other sites and finally did it. It is working quite good, white is white and black is black and the contrast is high. Is hard to show the results on forum, look better in reality.

130997130998

and the metering
130999131000

sensitivity 1 ASA and preflash (to get a light gray)


this are just 4x5 tests. I plan to shoot 5x7 or 8x10 portraits on paper.

[stiganas]

I got some questions by PM so I write further details here:

the process:
- first developer - you got a negative image - this is the only step where you can make adjustments
- bleach - you dissolve away the negative image (Ag) the paper is white again.
from here you can turn on the light (in fact you need to turn the light on)
- clearing - just to wash the chemicals from the bleach
- second developer - you got the final image - positive - not much to do here
- fix - just in case, not truly necessary.
I rinse after each step, I don't want to cross contaminate my chemicals.

I used for testing regular paper developer (Foma) - I plan to try highly diluted Rodinal - maybe I can tame the contrast a bit.

The test paper was fresh Adox MCP310.

Here come the tricky part. If you expose the paper like for "regular" paper negatives you got a nice negative in the tray but the final image will be to dark. Like this:
131040

There is to much silver halide in the paper. So you have to do two things:
- flash the paper
- overexpose.
Find a balance between the two. You have no room for errors like always in transparencies.

For the flashing part I just use some paper scraps and flash them in my darkroom (bathroom), develop and inspect. I aimed to a nice uniform light gray.
For the exposure I set the sensitivity at 1 ASA.
With this the picture will be almost black in the first tray.

Recipes:
I start with this ones:
Less is More by Ed Buffaloe
http://unblinkingeye.com/Articles/NbyR/NbyR2/nbyr2.html

bleach : Kodak R-21A Reversal Bleach
Distilled Water
700 ml
Potassium Dichromate
50 g
Concentrated Sulphuric Acid
50 ml
Distilled Water to Make
1 liter
Dilute 1:9 for use, and discard after 1 session (I don't discard, it is working fine a long time)
time 1 minute

clearing:
Kodak R-21B Clearing Bath
Sodium Sulphite
50 g
Sodium Hydroxide (I didn't use it, just the sulphite)
1 g
Water to Make
1 liter
time 3 minutes

I read that you can replace the nasty sulphuric acid with sodium bisulfate (ultra cheap as pH minus for pools).
From APUG:
sodium bisulfate (65 g/L) and potassium dichromate (10 g/L) - I don't have the link.
The bleach and clearing are very flexible, work to completion over a large range of concentration, nothing critical here.

That is all.

[stiganas]

I've done some test outside and the results are good.

start
131220

more image
131221

final negative image
131222

final positive
131223

I'll try next more preflash and less exposure. Even in bright sun I need a long time and wide open.

[Liquid Artist]

I am wondering if we could do something similar with color paper.

More specifically I wonder if we can make prints from slides using a similar technique.

[chrism]

You would be re-creating the Ilfochrome/Cibachrome process. Very complicated!

[stiganas]

I've done more experiments and even some "real" photos. I increase the preflash until the final black in the positive was not black anymore.

Even so I have to meter the paper at ISO 2-4 to get a good image.

132302

Some scans.

5x7 originals
132303 132304
4x5 original
132305

Some observations about the chemicals.
The paper developer is exhausted fast because it has to develop all the silver in the paper.
The (labeled one shot) diluted bleach keeps going. You cannot make mistakes because is either working dissolving all Ag or not, mine is still working fast, less than 30s.
The clearing bath have little to do so I think will be good for years.
The fix bath is just as a precaution, on a complete reversed paper has nothing to fix.

Next step I'll try permanganate bleach.

[Randy]

Stiganas, thanks for all the great information and examples - you have given me a great starting point.