Suitable characteristics for interpositive

Hi,

I am about to embark on making 16x20 enlarged negatives from 8x10 for Pt/Pd printing.

I am using regular panchromatic films for making interpositive and ortho films for enlarged negative both processed in a pyro developer. I did read Bob Herbst article on it got the just of it.

I am trying to find out what sort of films would be suitable for making interpostives based on its characteristics. Simply because I am thinking of using more economical films rather than Tri-X or Tmax 100.

Also, is there any advantage of using pryo developer in this process? That is what Bob Herbst uses. I am also wondering if I can use, say, Pyrocat for this.

Is there books or articles that I can read to get more understanding of this issue? Any suggestions will be appreciated.

Warmly,
Tsuyoshi

why don't you just try what you've got on hand and see how it goes

Since the desired characteristic of an interpositive is a relatively flat (low contrast) film representation of the original camera negative any film with a relatively flat response will work. I would consider using 100 speed film as opposed to the higher speed films that you mentioned. The extra two stops are just that much more difficult to expose accurately under an enlarger.

To repeat...the rule is flat with all information shown.

Tsuyoshi,

I use APHS film for both interpositives, and direct reversal negatives. There's a very helpful article in the unblinking eye website by Ed Buffaloe on using APHS as direct reversal negatives for working with alternative processes. The good thing about direct reversal is that you end up with an enlarged negative in one step, thus dispensing with the interpositive stage. It's a little more work, and involves a period of testing, but for me the initial extra effort pays off by the amount of work it saves further down the line.

I am in the process of arriving at workable combinations between APHS and off-the-shelf low-contrast developers, as well as Dave Soemarko's LC-1 and LC-1B formulations which he developed precisely for APHS and enlarged negatives. If you're interested in my preliminary results, PM me. They're not quite all there yet, but I've got a few good starting points lined up.

Jim Galli had an APUG posting about using APHS as taking film, and using a very dilute Rodinal and very dilute benzotrizole and pot. iodide solution for taming the inherent high-contrast APHS lith film into submission. It's a useful reference as well.

Just use Ortho film from any of the suppliers. You will need to waste a few cut up strips testing to see how it reacts. Here are a couple of examples, one of a test strip and the other the final interpositive. You want a flat image. There are many ways to do it.

Thanks for your reply.

I just ordered 16x20 Ortho films and Arista Ultra 100 to give a try. I have some J&C pro for interpositive as well.

We will see how it goes.

Warmly,
Tsuyoshi