How to duplicate film?

[pkr1979]

Hi all,

If one wants to duplicate film - how do you expose? ISO and exposure time is known, but how is the absence of aperture calculated into this equation?

Cheers
Peter

 

[koraks]

ISO and exposure time is known

No, they're not, really. That's part of the tricky bit.

To duplicate negatives and preserve the original contrast, you'll have to work out exposure + development. The usual way of doing this is through a sequence of test strips. You'll find that an enlarger is generally too intense a light source and you'll probably have to use an ND filter to tone it down lots.

 

[pkr1979]

No, they're not, really. That's part of the tricky bit.

To duplicate negatives and preserve the original contrast, you'll have to work out exposure + development. The usual way of doing this is through a sequence of test strips. You'll find that an enlarger is generally too intense a light source and you'll probably have to use an ND filter to tone it down lots.

Im not saying we know the exact exposure time as its difficult to know without knowing the aperture, but we can take the time and know for how long we have made an exposure. And the ISO we do know...or?

 

[koraks]

Well, you said it: "...or".
Keep in mind you're not exposing the film in a camera to a normal brightness range scene. It's a different application. The actual film speed will still be around 100 ISO, but this information won't help you all that much.

As I said, make test strips and be prepared to have to dial back the light level of your light source. Forget about film speed ISO ratings; they're not very relevant in this context. All you need to realize is that the film will be several stops faster than regular printing paper. This is sufficient to get you in the ballpark. Exact exposure will still have to be determined empirically.

Also, are you planning to do reversal processing or will you work with an interpositive, so two generations towards a duplicate?

 

[jeffreyg]

Back when I was practicing before we had digital we had to duplicate X-rays for insurance purposes. I used X-ray duplicating film and made a very simple light source from parts from the hardware store and a 15w bulb and a piece of glass. After determining the height the bulb had to be above the glass I ended up with 30 seconds exposure in a dark room. Now I sometimes use that film to make enlarged negatives for pt/pd prints. It makes perfect negatives

 

[Donald Qualls]

I used X-ray duplicating film

That film, however, was made for your exact use, and was no more than a stop faster than modern multigrade enlarging paper.

If you manage to cut the exposure back to something you could manage with an enlarging timer, you also have to account for reciprocity departure -- which will boost contrast again and require pulling development some more. It might be better to work with a very short exposure (the way commercial film duplicators do). Ideally, you'd get one of those machines in the first place...

 

[Nicholas Lindan]

You could also try a slide duplicator.

You say duplicate - are you planning on making:

• Positive transparencies from negative images;
• Positive transparencies from positive transparencies;
• Duplicate negatives from negative images;
• Negatives from positive transparencies?

Stay away from the Leitz Eldia - possibly the cheapest thing you can buy that says Leitz on it. Notice that all the ones for sale are in "mint unused condition." They are dust magnets, unbelievable dust magnets.

 

[pkr1979]

Now I was thinking about making a black and white negative from positive color film - to make a black and white print.

 

[BobUK]

I have copied colour slides onto black and white film using an Olympus bellows and camera with through the lens metering. The Olympus bellows have an accessory that hold either a 35mm mounted slide or strip of negatives. Olympus flash set on auto was positioned about a foot behind the slides. There is a built in light diffuser fitted to the accessory, but for good measure I hung a sheet of lighting diffuser between flash and the slide holding negative.
I ran a test of about ten shots. The results were were all good.
The camera fits on one end of the bellows and the lens fits on the other, then the accessory slide/film holder.
Aperture was selected from the guide on the flash.
No calculations and good results.
I did make notes of distances etc. for future use.

 

[Donald Qualls]

Yep, for making B&W negatives from color slides, a slide duplicator is exactly the right equipment.

 

[jeffreyg]

That film, however, was made for your exact use, and was no more than a stop faster than modern multigrade enlarging paper.

If you manage to cut the exposure back to something you could manage with an enlarging timer, you also have to account for reciprocity departure -- which will boost contrast again and require pulling development some more. It might be better to work with a very short exposure (the way commercial film duplicators do). Ideally, you'd get one of those machines in the first place...

I have used that film to enlarge to from original 2 1/4 and 4x5 to larger negatives for pt/pd prints. I have made at least 100 negatives that way most 8x10 some 11x14. With my enlarger light source the exposure times were much longer than with paper prints. Never had problems with reciprocity or development. I now see he wants to go from color to black and white. I can’t comment on that because I never tried that.

 

[DREW WILEY]

OK. A positive chrome to a black and white negative. I've done many of those.

1) What film format is the original? That will determine whether the task is best done via contact, emulsion to emulsion, or by projection (enlargement) instead. There are specific equipment implications to these choices. (Slide duplicators are a rather imprecise way to go about it, and work only in the realm of 35mm to 35mm anyway).

2) You are starting out with a contrasty original, a chrome, so need to strategize how you are going to handle that with your internegative black and white film. I recommend a panchromatic film with a long straight line to it, along with fine grain, like FP4 or TMax 100. Being panchromatic means that you can use contrast filters to selectively alter scene values in the chrome just like working with natural light when shooting black and white film. Just realize that enlarger bulb light is itself somewhat on the warm side (yellowish) if not filter modified.

3) I'm going to skip over some of the minor steps like filter factors and aperture settings, because, in the final analysis, you're just going to have to waste some black and white film experimentally doing testing to arrive at the sweet spot. It's not that difficult if you're patient and keep notes. I happen to have some very precise easel densitometers that makes this whole process relatively easy for me, image to image. But every now and then I get thrown a curve ball. Instrumentation is a luxury in this case, but not a necessity.

Some people start by trying to duplicate the scale of a step wedge, others just dive right in with the image in question. Try to get the full dynamic range of the original within the printable density of the b&w internegative itself. Consider mistakes just part of the learning curve. In other words, have fun doing it. Once you've acquired the basic skills, it becomes relatively intuitive.

 

[pkr1979]

8x10 color positive to 8x10 bw negative to 8x10 bw copy.

 

[DREW WILEY]

Do that by emulsion-to-emulsion contact in a good clean contact frame. You can use an enlarger as the exposing light source, preferably a colorhead adjusted to 5000K, then tweaked if necessary with the right B&W contrast filter. My own 8X10 frame is equipped with registration pins and a matching film punch, which is certainly convenient, but not necessary for casual work where multiple intermediate film steps are not involved. It also helps to have anti-Newton glass in the contact frame if you're in a damp climate like me, but there are workarounds for that too. I only have passive electrical heating in my darkroom during winter, and not drier forced air heat. So I try to do most of my film registration projects in the Fall, which is our least humid season here.

 

[Chan Tran]

The aperture? Not very important. It should be small enough to have some depth of field to cover problem of film flatness but not too small so that diffraction would cause problem. The ISO should be low enough to have good resolution because there is no advantage in higher ISO. Now you have only the exposure time and it should be set for the light source. That is it would expose so that the light source with out the original in place would barely reach the burn out point. Anything darker should have good details. That's all.

 

[pkr1979]

Do that by emulsion-to-emulsion contact in a good clean contact frame. You can use an enlarger as the exposing light source, preferably a colorhead adjusted to 5000K, then tweaked if necessary with the right B&W contrast filter. My own 8X10 frame is equipped with registration pins and a matching film punch, which is certainly convenient, but not necessary for casual work where multiple intermediate film steps are not involved. It also helps to have anti-Newton glass in the contact frame if you're in a damp climate like me, but there are workarounds for that too. I only have passive electrical heating in my darkroom during winter, and not drier forced air heat. So I try to do most of my film registration projects in the Fall, which is our least humid season here.

Thanks. I got the equipment I need then... What kind of exposure times are we talking about in a set up like this?

 

[ic-racer]

I use my enlarger to project the image directly onto film.

My fancy "film holder" is actually a Rollie 6008i body which, conveniently, contains a TTL meter that lets me know the exposure time.

I have done it two ways that both work:

A) Set the camera to B and use the enlarger's timer

B) Use the camera's mirror as a makeshift shutter with the cameras timer (only good for exposures greater than 1 second).

 

[DREW WILEY]

pkr - enlarger light sources obviously differ somewhat from one another. Mine are all relatively powerful. But I aim for an exposure long enough to be easily monitored at full output, but not so long as to cause major reciprocity failure issues. Typically, I standardize on either 10 seconds or 20, and otherwise adjust via aperture control.

If a hard contrast filter is also in the light path, that help slow down exposure times. And since you are going to do this by contact, you can use just about any aperture you want as long as the coverage circle of light is completely uniform across the contact frame itself. Since my weakest colorhead is still 750W, and has the most precise feedback loop, I might stop down the lens even to f/45 to get my target 10 sec time. ND filters are also a possibility.

Making the internegs via enlargement is a somewhat different question; and I only do that with high-end apo lenses made for close range reproduction, and using a pin-registered vacuum board or specialized vacuum sheet film holder. By comparison, working with an 8x10 film original via contact is sheer luxury, and will deliver superior results. You can select from any number of common developers, but with large sheets of film, HC-110 is nice because it responds so well to different levels of dilution. But even basic D76 will do a decent job.

You want to get the full dynamic range of the chrome onto the straight line section of the duplication film. Because TMax 100 has more shadow linearity than FP4, it requires only half as much exposure, but either film will do an excellent job, because both films were designed with such applications in mind (most b&w films were not). Of course there are all kinds of supplementary tricks to potentially improve the result, including masking techniques. But you want to master the basics first.

One of the bigger problems is simply learning to recognize which chromes are excellent candidates for b&w film conversion, and which or not. The prints can have special dramatic look hard to attain by conventional means. I drymounted several of those last week, generated from old LF chromes. But sometimes a chrome is just too contrasty to begin with. Heaven help you if the original was shot on Velvia; but once in awhile even one of those will turn out well.

 

[Don_ih]

Best quality would be contact printing the 8x10 colour onto 8x10 b&w. But if you can't manage to eliminate newton rings or dust (dust can be on 5 different surfaces in this light path), you can always backlight your 8x10 transparency and take a photo of it with a camera (any format). That will be a bit lower quality than the contact print, but still very good.

 

[DREW WILEY]

With a lightbox you still have 3 surfaces to contend with in terms of dust, and in an open setting. There's just no way of getting around working clean to begin with. And a lightbox itself still has a smooth surface capable of producing rings if your film is truly flat.

Sometimes a piece of drafting mylar (Duralar etc, not acetate), frosted on both sides, can be put in between a smooth contact glass and the back of the transparency. This works best if there are no large textureless areas in the image itself, like an open sky. But the emulsion to emulsion contact itself is much less susceptible to rings. It's a pity that so few sheet films today no longer have a retouching "tooth" surface to them. But the current Kodak chrome and color neg sheets do have a slight surface change alleged to improve scanning, which also seems to help the Newton ring issue somewhat.

A basic duplication project like this is still fairly easy; and a sheet of 8X10 black and white film in terms of an internegative is large enough to easily retouch or spot a bit if necessary. Once one gets into multiple registered masks total dust control can be more nerve wracking.

I once made many master duplicate chromes for sake of Ciba printing with all the refinements loaded into the final master chrome, and where nearly any kind of retouching or spotting was unrealistic. The worst instance involved 13 total stages of registration (counting a subsequent step using the same master chrome dupe to generate a master 8X10 color interneg for sake of RA4 printing too); but the effort was worth it in terms of visual result. But all of that came out completely clean. I wonder if I'd ever have that kind of patience again. Now three steps are about my routine limit.

 

[Don_ih]

With a lightbox you still have 3 surfaces to contend with in terms of dust, and in an open setting. There's just no way of getting around working clean to begin with. And a lightbox itself still has a smooth surface capable of producing rings if your film is truly flat.

The film can be held off the surface of the lightbox, so no rings whatsoever. Sagging may be a problem. At any rate, it's a definite second-best to contact copying.

 

[DREW WILEY]

More like a third or fourth best. I've done that atop a lightbox approach for relatively casual quick purposes, like web-presentable commercial images. But yeah, it's kinda like the debate over glassless neg carriers and trying to stretch the sheet of film taut, which sorta works too, but not for critical purposes or anytime registration of more than one sheet of film is involved.

There was an era of more than a decade when good stiff PET base was simply unavailable for most color sheet films. Acetate base not only sags more easily, but isn't dimensionally stable, so won't retain registration with masks etc for very long. That's one reason I resorted to the extra work of master printing dupes. And with cameras, I had to use adhesive film holders if any significant amount of enlargement was contemplated, or else there would be an evident compromise to sharpness due to potential film sag or bow in the holder. That's was far less a problem in black and white shooting because, in that case, most sheet films remained PET base, and I don't personally enlarge b&w larger than 20X24.

 

[Don_ih]

More like a third or fourth best.

Perhaps you can actually name what 2nd and 3rd would be? Without mentioning scanners or digital cameras, that is. Is second best breaking out the colouring pencils and sketchbook?

We're not talking about enlarging or registration of masks or anything. It's a copy of a transparency. When copying with a camera, the sag that would be an enormous problem when enlarging becomes less of one due to depth of field. Once again, not as good as a contact print. But if a contact print isn't going to work, this is possible. Also, you can copy an 8x10 transparency to 4x5 film using a camera - you can't do it via contact printing. Well, I guess you could tile the 4x5 film....

 

[DREW WILEY]

Projection techniques, precision enlarger carrier to precision vac board or vac film holder. 1:1 is attainable with the right graphics process lenses and enlargers with sufficient bellows extension.

In terms of mismatched size contacts, I've done that hundreds of times. One punches a register strip and tapes it to the smaller original, such as 120 film, and then contacts that to a 4x5 sheet. That's been standard practice for decades, particular in relation to masking techniques.

Scanning or digital photog is an entirely different ballgame, because then you're ordinarily restricted to digital output too. Smudge pencils sometimes still come in handy for retouching and casual masking purposes, on the black and white film itself, that is, or preferably on a registered sheet of frosted mylar. Cave painters invented that kind of shading, though I doubt they had mylar back then, maybe greased mastodon hides, too wooly to cause N-ring problems.

 

[Don_ih]

Contact printing 120 to 4x5 is pretty easy. Contact printing 8x10 to 35mm would be a bit of a harsh crop.