Enlarged Film Negatives Process?

[LFLarry]

Okay... I get it now...

I can try this as my first venture into making an enlarged negative because I have everything I need on hand already.

I mostly shoot FP4 in both 4x5 and 8x10, so I will take an FP4 4x5 negative and make a 4x5 Interpositive.
Then, I will load the new Interpositive in the enlarger and make a new enlarged 8x10 negative.

Based on Jim's advice above for Lith film above, it appears this should apply to this scenario too:

The inter-positive is both overexposed and underdeveloped so the highlights are dark and shadows are weak.

Highlights are controlled by exposure and shadows by development.

For the new enlarged negative, print for the shadows (think areas on negative) and alter highlights via development.

Anything else as far as guidelines or principals that I should consider before jumping in?

No reversal needed. It's a 2-step, 2-sheet of film process. A negative of a negative is a positive, or in this case termed an interpositive or diapositive. You first make this interpositive, preferably by contact on something a lot more predictable and flexible to development than lith film, and then enlarge that interpositive onto lith film or whatever for sake of the full-sized printing negative.

[Drew Wiley]

Yes, you're getting it. It's really simple in principle. You want your interpositive slightly overexposed but underdeveloped, so that all the tonality information will be on it. That is a lot easier to do well with a conventional film rather than lith film. Then the enlarged negative can be more fully developed for the degree of contrast you need to effectively print with. You could use conventional film for both; but ULF sheets of a film like FP4 are rather expensive, while lith is comparatively cheap, but can be frustrating to initially get good results with. I went though that route a couple years ago just for fun, but the usage of lith made it a longer than anticipated project. Since I don't contact print any larger than 8x10, I'd far rather use two sheets of TMX or perhaps dig into my stash of Tech Pan 8x10 for sake of a high contrast neg. Lith was a headache.

[Drew Wiley]

Yes, you're getting it. It's really simple in principle. You want your interpositive slightly overexposed but underdeveloped, so that all the tonality information will be on it. That is a lot easier to do well with a conventional film rather than lith film. Then the enlarged negative can be more fully developed for the degree of contrast you need to effectively print with. You could use conventional film for both; but ULF sheets of a film like FP4 are rather expensive, while lith is comparatively cheap, but can be frustrating to initially get good results with. I went though that route a couple years ago just for fun, but the usage of lith made it a longer than anticipated project. Since I don't contact print any larger than 8x10, I'd far rather use two sheets of TMX or perhaps dig into my stash of Tech Pan 8x10 for sake of a high contrast neg. Lith was a headache. I learned how do it well on ordinary sheet film long ago, almost as a beginner to black and white.

[LFLarry]

Thanks, Drew. I feel like I have a solid place to start my testing now. I am really excited about this.

It seems that T-Max 100 is used for this pretty frequently. Do you have any experience or opinion about using FP4 vs. T-Max 100?

Yes, you're getting it. It's really simple in principle. You want your interpositive slightly overexposed but underdeveloped, so that all the tonality information will be on it. That is a lot easier to do well with a conventional film rather than lith film. Then the enlarged negative can be more fully developed for the degree of contrast you need to effectively print with. You could use conventional film for both; but ULF sheets of a film like FP4 are rather expensive, while lith is comparatively cheap, but can be frustrating to initially get good results with. I went though that route a couple years ago just for fun, but the usage of lith made it a longer than anticipated project. Since I don't contact print any larger than 8x10, I'd far rather use two sheets of TMX or perhaps dig into my stash of Tech Pan 8x10 for sake of a high contrast neg. Lith was a headache.

[Tin Can]

Addendum

I used X-Ray film for my first image, as I couldn't meter the inside of a powered up light bulb. X-Ray is cheap, I used it as 'Polaroid' shooting and quickly processing a minute later many iterations

and my scene was high contrast, good for X-Ray, then used FP4+ to make the internegative and enlarged with that

[LFLarry]

That is an interesting idea to use X-Ray film in that way. Thanks for sharing.

Addendum

I used X-Ray film for my first image, as I couldn't meter the inside of a powered up light bulb. X-Ray is cheap, I used it as 'Polaroid' shooting and quickly processing a minute later many iterations

and my scene was high contrast, good for X-Ray, then used FP4+ to make the internegative and enlarged with that

[Drew Wiley]

OK, TMX 100 versus FP4. Either work well for large format originals; but I prefer TMax 100 with smaller film originals due to its finer grain. TMax can also be developed to a higher contrast if that is necessary, and it is one speed faster in this kind application than FP4 due to its longer straight line. Of course, you have to adjust the speed/exposure of either film for the warmer temperature of typical enlarger light sources. This is best done by testing and not just estimation. FP4 has the advantage of being a little cheaper. I keep both films on hand for both lab and general shooting purposes, and have curves plotted for both, just to keep my options open. The pink antihalation dye washes completely washes out of TMax, but there always seems to be about .04 density of it left over with FP4, which can be a minor issue for color film masking, but of little interest in this enlarged b&w neg case.

[LFLarry]

Very helpful and some really good points.

Bummer you can't find T-Max 100 in 8x10 which is a deal-breaker for me.

Thanks, Drew.

OK, TMX 100 versus FP4. Either work well for large format originals; but I prefer TMax 100 with smaller film originals due to its finer grain. TMax can also be developed to a higher contrast if that is necessary, and it is one speed faster in this kind application than FP4 due to its longer straight line. Of course, you have to adjust the speed/exposure of either film for the warmer temperature of typical enlarger light sources. This is best done by testing and not just estimation. FP4 has the advantage of being a little cheaper. I keep both films on hand for both lab and general shooting purposes, and have curves plotted for both, just to keep my options open. The pink antihalation dye washes completely washes out of TMax, but there always seems to be about .04 density of it left over with FP4, which can be a minor issue for color film masking, but of little interest in this enlarged b&w neg case.

[peter schrager]

Bergger has come out with new dupe film....check it out
made special for duping

[Drew Wiley]

I've never had any problem getting either speed of TMax in 8x10. But like certain other commodities it can temporarily run out at certain dealers. I recommend getting on Keith Canham's list.