What got me thinking about this was a very underexposed negative that I took on Ron Mowrey's AZO emulsion; made at the Rochester workshop and coated on melinex film. Not knowing the speed really, I had to guess, and the result was the thinnest neg you can imagine! But, it exhibited a positive image against a darkground quite well, exactly like an ambrotype or a tintype; which are effectively just underexposed negatives. Most people are familiar with the phenomenon, particularly with a film like Delta 3200 or something. But I'm wondering if there's some way to really accentuate the effect with normal medium/slow speed films; TXP320, Delta 100, etc. Are there some kind of "tricks" you can employ in the developer, or do you have to rely on gross underexposure? That latter's not an ideal solution since it might ruin your tonal scale. I know that collodion folks often, or at least historically, would have had 2 different developing & exposure schemes. 1 to produce a good negative and the other 2 produce a good positive. I wonder if we can gleem anything by comparing two such recipes... Now imagine if you could get a good "positive" developer in a monobath. Jeez... you might be able to set up shop on a streetcorner and start producing one off positives for folks!, assuming you also found a nice way to mount the film. Looking forward to your input!