Printing RA-4 with "three-color" filters - 3 separate exposures, 1 sheet of paper

[holmburgers]

Hey,

So I've stumbled across something that I'm curious about. I picked up quite a few wratten filters and whilst reading about them in the booklet "Kodak Filters for Scientific and Technical Uses" came across this interesting prospect.

Straight from the book....

"Printing with "Three-Color" Filters. Color print materials are sometimes printed with separate red-, green- and blue-light exposures rather than with filtered white light. The exposure through each filter is varied independently to control the color balance of the print. One such three-filter combination is KODAK WRATTEN Filters No. 25 (red), No. 99 (green), and No. 98 (blue). These filters, whose spectrophotometric curves are displayed below, are suitable for printing Kodak color negative products on Kodak color print materials (both film and paper)."

Now, doesn't this seem enticing? It seems to me like this would give you the ability to control color balance more akin to dye-transfer or tri-color carbon. That is, having complete control over the exposure of each individual color. Or, does this really provide an advantage?

Is anybody out there doing this? What do you think, intrigued enough to give it a shot?

Look forward to your comments,

Cheers!

 

[Photo Engineer]

I believe that there is someone doing this here. There was a thread on this a while back. We used 98,99 and 70 though as the 25 was rather broad.

PE

When all is said and done, more is said than done. (Bob Bacon, emulsion engineer)

 

[holmburgers]

Interesting... it does seem like a 25 wouldn't be very sharp. I'll see if I can't find this other thread; a link would be most appreciated!

They suggest 29 red, 61 green and 47B blue for Kodachrome/Ektachrome printed in the same manner. These of course are the classic color-separation filters for seps from real life. Why wouldn't the same be suitable for negative films? My guess would be that it is the orange mask, or maybe I'm missing something else.

 

[Tim Gray]

In several of the Kodak Endura spec sheets, they recommend using 25, 99, and 47B filters for tricolor exposures. They also give you ratios for starting times as well as what to change if color balance is off.

 

[Photo Engineer]

I don't have the thread reference, sorry. I have done a little of this type of printing and it is a real pain. You tend to get unsharp images due to enlarger shake or registration problems, and color balance is difficult to judge.

OTOH, you get brighter colors as there is less crosstalk. I have some examples around here somewhere and the difference is striking.

PE

 

[jpberger]

Just to clarify--- are we talking printing positives on ra-4 or negatives? This would be interesting to try with b/w separation negs, but methinks getting the registration right would be a project in itself.

 

[holmburgers]

Am I correct in my assumption that this makes printing on RA-4 more like DT/carbro? At least in terms of control of color values.

If you say the difference is striking, then that's good enough for me. Yes, registration would be a real pain I bet.

Come to think of it... you could print black & white separation negatives in this manner as well, couldn't you!? And... that means that ultimately you could mix the color channels and achieve effects akin to EIR, etc. (there was a url link here which no longer exists)

This whole notion is new to me, that you could do multiple exposures on one sheet; hence the excitement.

Thanks for the responses!

edit: yeah, good point jpberger on registering the sep negs being incredibly difficult....

 

[AgX]

There were special enlargers/colour heads (Agfa, Philips) employing this concept.

 

[Photo Engineer]

Actually, it is all of the above. You can do any of the things mentioned above as long as you balance the exposures properly and as long as you can register the 3 separations in the final image.

I used a vacuum register board and a punch for some work with negatives and prints, with others I just used an ordinary easel and the Kodak tri-color print wheel which they used to make for mounting below the lens. It minimized any motion you might have and was therefore easy to retain registration.

What it does in separate the 3 color images more than white light exposure does and therefore yellows, magentas, and reds are more vivid. Cyan and green are sometimes improved, but the RA4 paper and most films have such a far red that it does not cause a significant improvement. Using a WR70 did more than a 29 in this regard.

PE

 

[analogsnob]

This method of printing was used in machine printers of old and does produce cleaner colors. Enlarger printing does require an enlarger that is locked down firmly (read that as braced in all key areas) and if negatives or masks are to be switched between exposures a registered carrier is a requirement. Any combination of red green and blue will "work" the sharper cut filters giving more saturated colors when compared to the broader brothers. The effects are subtle and worth seeing for one's self if one has the time.

 

[EdSawyer]

Would this be any different, (other than being more of a pain in the ass!) than using the Minolta/Beseler 45A color head? That had separate red, green, and blue exposures through flashtubes and filters. You can adjust, fire, and change the channels independently, in 1% increments. PLus of course a very nice color analyzer built in....

-Ed

 

[Terrence Brennan]

Additive/subtractive printing

This method of printing was used in machine printers of old and does produce cleaner colors. Enlarger printing does require an enlarger that is locked down firmly (read that as braced in all key areas) and if negatives or masks are to be switched between exposures a registered carrier is a requirement. Any combination of red green and blue will "work" the sharper cut filters giving more saturated colors when compared to the broader brothers. The effects are subtle and worth seeing for one's self if one has the time.

You must be referring to really old photofinishing printers, which were additive printers: successive exposures through red, green & blue filters.

The Kodak S-series printers, and most other printers I encountered in 19 years in pro and amateur labs, were subtractive printers. These made an exposure which started with white light, and any two of the cyan, magenta and yellow filters would swing into the optical path, in various combinations, and the exposure would terminate when the third filter and the capping shutter swung in, in concert.

Exposure was determined by a series of six photo tubes, with two sets covered in a filter of the three additive primary (RGB) colours. A human operator would make density offsets, and could make colour offsets, as required.

The advantage to subtractive printers is that the exposure times tended to be shorter than for additive printers. All of the three CMY filters had a certain amount of "crosstalk," which I was told was designed into the system, to make the production of photofinishing-grade prints easier. I never has the opportunity to compare a negative printed on an S-series printer, with one printed via the additive method, with one printed in a standard CMY colour head enlarger, but I have no doubt that the other contributors to this thread are correct when they say that it made for brighter colors.

I spent more time than I care to remember dealing with S-series printers, with photographic and electro-mechanical maintenance problems. I wish I had a dollar for every time I set the slope centres or firing points on a printer!

 

[Photo Engineer]

Guys;

In the 50s there were 2 Kodak B&W printers, the model 3 and the model 4. The 3 was for small format, 35mm and 828 and smaller. The model 4 was for MF or 620, 120, 616 and etc. The Consent Decree made it mandatory for Kodak to supply a color printer for photofinishers so they produced the model 5 which worked for all formats and used 3 color exposures for printing. I never used one of these, as we only made enlargements using CC filters, but I have seen the model 5 and have heard that it was a beast and very slow.

Prints were developed on reels in 8x10 baskets in lengths of about 50 feet. Manual and Nitrogen burst agitation was used and the process took about 1 hour.

Just a bit of history. I ran that process so often that I vowed to change it if I ever worked for EK. Well, my wish came true!

PE

 

[nyoung]

I never printed with three separate exposures but I think I may try it now. I've used a Phillips PCS 150 additive (RGB) color head for over 20 years and I find it easier to dial in the color balance and maintain a balance through several prints than on a dichroic (subtractive) machine. RGB printing is particularly cool for printing transparencies on Ciba/Ilfochrome if you can afford it now-a-days.

 

[holmburgers]

If anyone has the means to make two comparison prints from the same negative and post them, it would be a great resource for everyone interested. I doubt if there's such n example anywhere on the internet.

nyoung (neil young? ), if you try it, please let us know!

 

[Photo Engineer]

If anyone has the means to make two comparison prints from the same negative and post them, it would be a great resource for everyone interested. I doubt if there's such n example anywhere on the internet.

nyoung (neil young? ), if you try it, please let us know!

I may have one here. If I do though, I cannot post the entire photo as I don't have rights to the model used.

PE

 

[holmburgers]

No worries, something's always better than nothing.

 

[hrst]

Is there a filter with three narrow passbands at R, G and B, that would change white light to trichromatic RGB "white"? It would give the same saturation boost by lowering crosstalk with white-light source, but with single exposure.

Another option would be to use RGB LED source, but the most common ones wouldn't probably have the best possible wavelengths so we would again have some crosstalk.

 

[Photo Engineer]

No worries, something's always better than nothing.

I've got nothing. The folder included some prints, but none with R/G/B exposure so I remembered wrong. Sorry. If I do find something, I'll scan and post, but I doubt it now.

PE

 

[Photo Engineer]

Is there a filter with three narrow passbands at R, G and B, that would change white light to trichromatic RGB "white"? It would give the same saturation boost by lowering crosstalk with white-light source, but with single exposure.

Another option would be to use RGB LED source, but the most common ones wouldn't probably have the best possible wavelengths so we would again have some crosstalk.

The basic problem here is that the final "white" that you want is not daylight "white", but rather a reddish Tungsten "white". And, to get this Tungsten balance, you have to fiddle with the quantity of light passed by each filter.

To do that, you must give unequal exposures through each filter or use CC filters if you try to use the "white" produced by juxtaposition of the output of each of the 3 during exposure.

PE

 

[nyoung]

nyoung (neil young? ), if you try it, please let us know![/QUOTE]

Sadly, all darkroom except for changing bags and developing tanks is packed away pending completion of the house remodel. I will try a comparison as soon as I get set up again but it will probably be in the deep winter (February).

For those who aren't familiar with the Phillips enlargers, the color head uses three halogen lamps illuminating through three narrow pass filters that can be individually controlled so it would be very easy to expose the red channel, then the green and then the blue. Normally, you use all three at once.

 

[EdSawyer]

If/when I get a condenser head, I could post examples. I have 4 of the Minolta/beseler 45A heads, that's my main color head. I've printed with dicrho heads and condensor head with filters in drawer also. I don't recall there being huge color differences between the methods. for B&W I use an Aristo head. (all on a 45-VXL)

The Minolta/Beseler 45A is a nice head. One can be picked up on ebay, complete, for less than the price of one or two of the hard-to-find replacement flashtubes. Thats' why I have 4. One for use, and 3 for spares, complete with tubes. It was a $2500+ head back in the day.

-Ed

 

[randyB]

Back in the 70's Unicolor had an color printing kit based on the Tri-color method. It had a color/exposure calculator that required only one test print for each negative. The Tri-color filter holder fit on the enlarging lens the way an under the lens Polycontrast filter holder fits. The system was a bit of a pain to use but the color was excellant especially with bigger negs. ( 6x6 to 4x5 ). I still have my set and I may use it again--someday. RandyB

 

[nyoung]

Is there a filter with three narrow passbands at R, G and B, that would change white light to trichromatic RGB "white"? It would give the same saturation boost by lowering crosstalk with white-light source, but with single exposure.

Find yourself a Phillips PCS 150 color head. That's exactly how they work.

 

[Karl_CTPhoto]

RGB printing can be very fast and efficient, far more efficient than CMY subtractive printing, because instead of *filtering* colors out, subtractively, you are making three rapid additive exposures.

That is with machines. In practice, manually, it will take longer. Ron raises an interesting point about the color temperature of the bulb.

I'm not sure if there was a standard for professional color printers (of course, bulbs changed and darkened over their lives so nothing is perfect in terms of color temperature except in theor), but variance in lamp VOLTAGE will also vary color temp up to the rated voltage.


Personally, I'd try to avoid a filter wheel unless I had a very firmly planted enlarger. I'd be temped to just hold the filters at roughly the same distance under the enlarger lens, but then my hands aren't perfectly shake-free either ;-)

While there's "3x" the opportunity for shake to occur, the biggest advantage I can think of is less color drift with short exposures caused by the lamp cooling up and down that you get with subtractive printing. Pro lab printers had shutters even for RGB exposures, but I'd imagine that the bulb warm-up cool-dwn would be negligible with three exposures compared to a single subtractive one.

If you have a subtractive enlarger already, just use it though. . .