Enlarging slides with duplicating film

Hey all,
Recently stumbled upon a box of 8x10 CDU duplicating film and decided to move forward with my master plan. Few questions:

1. Exposure time calculation relative to color paper? Just want to get a starting point.
2. Is there any method to use a slide film like E100 or Provia in such a fashion? Obviously exposure would be a bit challenging with the faster film/reciprocity.

I've always seen the look of slides on the light table and felt that the optimal display method would be slides enlarged onto duplicating film and displayed on a light table.

I used some CDU duplicating film to contact print a 6x6cm negative a decade ago, but I don't believe I took any notes on what my exposure times were. I vaguely recall it being somewhat faster than negatives on RA4 paper with equivalent settings. Does anyone have any tips for calculating a good starting point exposure time for duplicating film with an enlarger? The box has some convenient color settings on it from the previous owner which I can try.

Say I'm using CDU duplicating film (expired, stored frozen) with an 80mm enlarging lens to magnify a 6x6 negative onto an 8x10, either at 8x8 square or cropped 10x10. It saw ISO 25 somewhere -- do people know what the relative ISO of Endura is?

--Nick

I guess vaguely related has anyone ever worked with the transparent display film? https://www.bhphotovideo.com/c/product/592250-REG/Kodak_1105287_4732_Endura_Transparency_RA.html

Gotta break out the piggy bank for that one...

You're going to have to do a LOT of testing to nail it I'm afraid Nicholas !
Firstly, you can't use Endura film for duplicating slides because it's a colour negative - positive system.

So just like any other 'blind' and fresh start up, you will need to test your printing with multiple exposures and colour balances - but for starters, try this.....
( assuming you're enlarging 120 / 6x6 to 10"x8" with a standard colour head enlarger with tungsten lamp ).

Set colour filters at 70C + 65Y
Stop the lens down by two stops.
Make several exposures across the sheet at .... 2" 4" 6" 8" 12"
Process, evaluate and test again.

Notes:
CDU is quite old now and much of it is off ( low D-max / low contrast / crossed curves ), so you may be on a losing battle before you start.

Dupe film speed can range from EI 10 to around EI 25 and is usually 'faster' than RA-4 paper.

Unless you're using a pro lab ( and spending a small fortune 10"x8" E-6 processing ), don't expect accurate matching - unfortunately it's just not possible with 'uncontrolled' home processing ( but might be good enough for lightbox displays ).

Every film type can have a different colour balance ( even the same manufacturer and type... eg. Fuji RDP / RHP / RA etc... ), so just test with one correctly exposed and processed transparency for starters.


Good luck !
John S

John Salim said:

You're going to have to do a LOT of testing to nail it I'm afraid Nicholas !
Firstly, you can't use Endura film for duplicating slides because it's a colour negative - positive system.

So just like any other 'blind' and fresh start up, you will need to test your printing with multiple exposures and colour balances - but for starters, try this.....
( assuming you're enlarging 120 / 6x6 to 10"x8" with a standard colour head enlarger with tungsten lamp ).

Set colour filters at 70C + 65Y
Stop the lens down by two stops.
Make several exposures across the sheet at .... 2" 4" 6" 8" 12"
Process, evaluate and test again.

Notes:
CDU is quite old now and much of it is off ( low D-max / low contrast / crossed curves ), so you may be on a losing battle before you start.

Dupe film speed can range from EI 10 to around EI 25 and is usually 'faster' than RA-4 paper.

Unless you're using a pro lab ( and spending a small fortune 10"x8" E-6 processing ), don't expect accurate matching - unfortunately it's just not possible with 'uncontrolled' home processing ( but might be good enough for lightbox displays ).

Every film type can have a different colour balance ( even the same manufacturer and type... eg. Fuji RDP / RHP / RA etc... ).


Good luck !
John S

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Thanks for the reply! I mostly shoot color negative film but occasionally you just need the Velvia but when I shoot it, I don't have a great workflow now that Ciba be ded so I'm resigned to scanning and the flat scanners leave something to be desired.. I've always loved the look for a slide on the light table but never found a way to replicate it well. I had a box of 4x5 duplicating film back in the day but I don't recall why I never actually tried enlarging with it (possibly it was the absurd turnaround time on test strips).

Re: the Endura film I've always thought the transparency film would be an interesting way to get a similar look as slides without having to source expired dupe film.

There's a filter value written on the box which I believe is similar to what you provide.

The good news is this box was stored frozen so if any is expected to be reasonable I think this would be it. There's also a stash of 35mm CDU from the same set which I may acquire since it was stored under similar conditions and would make great test strips.

I've done enough color over the years to be pretty good at maintaining temperature -- I'm pretty confident I can keep it within 0.5 degrees for the BW development step. I've never had substantial problems with developing color at home (admittedly most has been C41 where you get some enlarger control), plus my new Sous-Vide machine will obviate the need for splashing boiling water into the bin over the lengthy E6 development I'm also not super critical on exact color as long as it looks...well...good.

I'm going to grab the 35mm CDU when I'm back and run a blank strip through E6 to check D-max. I agree if it's not looking good on that front at a minimum I'm probably SOL, but I'm an optimist

I sold all my 8x10 CDU II. It was frozen, but hasn't been made in a long time. A bit of 8x10 CDU III turned up frozen in Europe. I've used em all - Kodak EDupe series, Fuji's CDU's. The best duping film ever was the last generation of Astia - Astia 100F; a major plus was that it was on dimensionally stable polyester base instead of acetate. Sold my last of that too. Just an hour ago I finished framing a print shot on 8x10 chrome film, then contrast masked for sake of a master printing chrome contacted onto Astia 100F for sake of Ciba printing. But I never got around to that picture, and Ciba supplies dried up. So I made a contact interneg of that master chrome using 8X10 Portra 160, and finally printed it on Fuji RA4 Crystal Archive paper about a week ago. A lot of work; but the quality of the color reproduction is superb. I have a lot of potentially excellent 4x5 and 8x10 chromes laying around; but just a few will be turned into internegs. For new work, I mainly shoot Ektar CN film and print it directly onto RA4 paper.

But here's what you can expect with old dupe film (even stored frozen), essentially reiterating what John already noted. Expect incurable highlight crossover along with generally anemic color. Regardless, any kind of duping requires a method of second-generation contrast control. I prefer masking, but commercial labs generally flashed the duping film. No current chrome films are going to do a good job duping; they just don't have a long enough scale of balanced hue neutrality. But you could experiment with the current E100 product, which is about as close as you're going to get with current options. Velvia would be a horrible choice. Use a color temp meter to adjust your colorhead settings to match the 5500K balance of the E100 chrome film, and then test for long-exp reciprocity offsets (shouldn't be too bad if you standardize at 10 sec exp). I have special custom equipment for duping and internegs, way way more accurate than how the labs did it. But if you want really good results, it doesn't come either cheap or easy.

If you decide to make contrast masks to attach to the originals for sake of dupes, make them like relatively gentle versions of masks for Ciba printing; dont go overboard. Most typical masks for duping should be around .30 to .45 DMax, depending. But that's relative to fresh duping film; with anything old, no telling, since its contrast will probably be out of whack anyway. I won't comment on the flashing option, since I don't do it.

Transparency display material is unrelated unless you want something backlit really big. Besides, do you really want to spend hundreds of dollars for a big roll of that?

I was curious if the transparency display material would produce a similar look. A lot of my current work is Ektar and Portra but I still shoot Velvia for the look.

So if I don’t contrast mask things are going to be a bit wild? That would be an adventure with un perforated film.

Masking is a complex subject in its own right. Ciba transparent display film had to be masked similarly to Ciba print material. But today's RA4 display materials need to either be laser printed after a scan, or directly from color negs via optical enlargement, or via some kind of interneg if a chrome original is involved. Velvia has very high contrast to begin with unless the original scene contrast itself was especially mild. That means, going straight to the repro stage - in this case, hypothetically a big transparency - either the highlights or low values, or both, will be nearly impossible to reproduce. The native high contrast of the Velvia original becomes exaggerated in the reproduction. Second, the dyes in Velvia aren't particularly compatible with those in most RA4 materials. The quality of color repro can be quite ifffy. I have gotten a number of superb RA4 prints from large format Velvia originals, but there's quite a trick to doing the internegs correctly. And I've had some bellyflops too, trying to find out just how far I could get away with this. A lot of work went into finding the sweet spot in the respective film curves. I don't want to discourage anyone, but am just being realistic. Better internegs than ever can be made with current film; but I can't personally imagine doing it well without masking.

Official interneg films were designed to do the task by themselves, often with supplementary flashing. With a typical Velvia original involved, you'd have to flash so strongly that the effect would carry across a range so wide that it would likely muddy up things across the board. But like I already stated, I simply don't flash in the lab, since I already have all the gear an experience necessary for very precise masking. (I do sometimes flash original film shots in the field, specifically Ektar to offset its cyan imbalance in shadows). Print flashing is more general, while masking can be highly targeted for specific hue and density distribution. Maybe someone else could coach you on flashing methods in the darkroom. If you enjoy experimenting, and can tolerate some inevitable bellyflops, then by all means, give it a try. But getting good consistent results seems to take quite a patient track record of surviving the bellyflops first.

DREW WILEY said:

Masking is a complex subject in its own right. Ciba transparent display film had to be masked similarly to Ciba print material. But today's RA4 display materials need to either be laser printed after a scan, or directly from color negs via optical enlargement, or via some kind of interneg if a chrome original is involved. Velvia has very high contrast to begin with unless the original scene contrast itself was especially mild. That means, going straight to the repro stage - in this case, hypothetically a big transparency - either the highlights or low values, or both, will be nearly impossible to reproduce. The native high contrast of the Velvia original becomes exaggerated in the reproduction. Second, the dyes in Velvia aren't particularly compatible with those in most RA4 materials. The quality of color repro can be quite ifffy. I have gotten a number of superb RA4 prints from large format Velvia originals, but there's quite a trick to doing the internegs correctly. And I've had some bellyflops too, trying to find out just how far I could get away with this. A lot of work went into finding the sweet spot in the respective film curves. I don't want to discourage anyone, but am just being realistic. Better internegs than ever can be made with current film; but I can't personally imagine doing it well without masking.

Official interneg films were designed to do the task by themselves, often with supplementary flashing. With a typical Velvia original involved, you'd have to flash so strongly that the effect would carry across a range so wide that it would likely muddy up things across the board. But like I already stated, I simply don't flash in the lab, since I already have all the gear an experience necessary for very precise masking. (I do sometimes flash original film shots in the field, specifically Ektar to offset its cyan imbalance in shadows). Print flashing is more general, while masking can be highly targeted for specific hue and density distribution. Maybe someone else could coach you on flashing methods in the darkroom. If you enjoy experimenting, and can tolerate some inevitable bellyflops, then by all means, give it a try. But getting good consistent results seems to take quite a patient track record of surviving the bellyflops first.

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Do you have any tips on "flashing?" Does it involve a calibrated uniform exposure or a repeat of the same?

I acquired about 150 ft of 35mm CDU from the same collection that I can use for test strips. I'm going to run a strip through E6 to check DMax and possibly try a test strip.

If at all possible I would like to try printing C41 negs on transparency display material. Someone will have to bite the bullet and trim down a steamroller though.