(Large format) Reversal processing paper for in-camera direct positive?

[J N]

I have 5x7 and 8x10 field cameras (permanently?) loaned to me by a friend, and they're in fine working order. I don't really have any interest in working with extra big sheet film, but I feel like I'll do paper negatives one of these days. However, I'm wondering if reversal processing might work.

Any experiences, advice, etc.?

Also I have a few jars of Black Magic and wonder what happens if you coat a mirror or transparent film with it, if it can be made to coat uniformly and stick?

 

[koraks]

There's of course Harman Direct Positive paper. Haven't tried it; it's high contrast, but it should work and I think some people have tried it in this application.

Yes, reversal processing works. With RC paper I usually got some degree of mottling due to the slightly uneven paper base, but YMMV as they say. When I experimented with this, I used a dichromate bleach, but a somewhat more sane potassium permanganate bleach should work, too. Strong peroxide and acid should work, too, but I've never tried this.

Contrast control will be the main challenge, but this is a matter of working out the parameters in terms of exposure and first developer chemistry. As in film processing, you'll likely need to add a silver halide solvent (thiosulfate, thiocyanate) to get rid of some of the excess density.

For an easier approach, consider simply shooting paper negatives and contact printing or photographing those.

 

[Ian Grant]

About a week ago I was told a company is nearly ready to market a Direct positive developer for B&W paper, I've been looking at Patents etc to see how this could work, so far I've not figured it out. It can be done Kodak made a Direct Reversal developer for Microfilm.

It would be relatively easy to do using two developers, the first B&W, stop and re-expose, then the second a simple Colour developer with the right balance of Colour couplers added, followed by bleach & fix. The hardest part would be getting the balance of couplers right. This is how colour reversal films work, the difference is the couplers are in the emulsion. layers.

Ian

 

[Molli]

I've made paper negatives in a basic 4x5 Calumet, a 6x9 Folder and a homemade stereo pinhole camera, all then reversal processed using Potassium Permanganate and Sodium Bisulphate (apologies for the typo in my write up!) as the bleach. This is a simplified process I found via "Analogue Photography Talk" on YouTube:

Below are some examples from each camera. The only downside to this process is the need to overexpose by three stops an already slow paper.
The splotches on the mannequin photograph with the light background are what happens if you don't mix in the permanganate fully
P.S. The stereo photo is a) boring and b) not swapped out right to left to work as scanned as a stereograph.

 

[Jaume Tormo]

Hi,

Look for Joe Van Cleave's YouTube channel, he has an interesting series on reversal proces with acid and peroxide. In collaboration with Ethan Moses.

Jaume