RA-4 filtration problem

[ekjt]

Now we have a nice thread on RA-4 filtration, so i'd like to ask you another thing.
How much do different processing chemicals effect your filtration? I have been quite surprised that the color filtration seems to be quite stable for a given negative-enlarger-paper combination regardless to which chemicals I have used as long as they are fresh or properly replenished. Even changing from Tetenal room temp chemicals to 35 C degree processing with Paterson chemistry made only around 2,5M difference with the neg I was printing.

 

[Ed Sukach]

Tough one. I usually get hooked on one brand of developing chemistry at a time. For the last 2-3 years it has been Tetenal, for a number of reasons - one of the most important is availability.
I have used Photocolor and I don't remember any *great* difference between Tetenal and Photocolor.
There IS a great difference between papers - Ilfocolor, Fuji, Agfa Signum, Kodak ... all require significantly different filtration. I had been using Ilfocolor (present and future status in doubt) for its consistency: *no* difference when using different sizes, very little lot-to-lot variability. I can't say the same for either Kodak or Agfa. I've just started with Fuji Crystal Archive, so I can't really comment on it yet.

2-3 cc Difference? I've seen about that much between frames on the same roll of film.

 

[Dave Starr]

Test Results
Yesterday, I was going to test the neg in question with Kodak paper rather than the Fuji I had the problem with. I found something, but I'm not sure it's the problem. When I was pouring the blix into the tray, I noticed a precipitate in the blix. I thought that was the source of the problem; bad blix. I mixed fresh chemistry and did some printing today. I made prints of the color checker frame with the different papers i had on hand. First, I used the filtration I'd gotten good prints with using the Kodak Supra paper - 45M, 80Y - & got a print with no color cast on the first try. Then I tried some Fuji P and got a good print with 15M, 50Y. When I tried the Fuji C I originally had the problem with, I went to 0M, 50Y and still had a slight cyan cast.

So, now I just don't know. Fresh chemistry, and still the same problem with the same paper. The other papers I tried look ok, so maybe it's the box of paper I got. Since I got good color balance with 2 papers, that does rule out UV fluorescence from the Color Checker. As expensive as they are, I doubted that Macbeth would use a fluorescing ink on them anyway.

At the very least, I've learned a lot from this. Thanks to everyone for their input and advice.

 

[Ed Sukach]

Since I got good color balance with 2 papers, that does rule out UV fluorescence from the Color Checker. As expensive as they are, I doubted that Macbeth would use a fluorescing ink on them anyway.

Does sound like a paper issue.

I was surprised, myself, about the MacBeth fluorescence - more than a little bit.

I'll see if I can find the original article.

 

[Dave Starr]

RETESTED
New film processed in new Tetenal C-41, new Tetenal RA-4, same Fuji paper that started this thread. First frame was the Color Checker, rest were daffodils & tulips. I got the color balance of the Color Checker right on. Filtration was 20C, 60Y, 0M. printed one of the flower frames & the color's dead on. The paper's fine, but the filtration's weird. All in all, quite a learning experience.

 

[Bob Carnie]

Dave
I find nothing unusual with your results by adding the cyan you have reached a good balance and that is all that is required.
When printing cibachrome I am continually in the cyan filter to balance the colour. You have just came across an unusual situation that you have solved by using the third filter available to you and zeroing out one filter.
As others have pointed out for colour negative printing one usually require only the yellow and magenta dials with the yellow number higher.

 

[Ed Sukach]

Interesting. I'm wondering ... are you using the proper lamp in the enlarger? And - what film, specifically, did you use?

Just curious. Certainly there is no "law" stating "Thou shalt NOT use cyan filtration", but I think it is a trifle unusual.

 

[Dave Starr]

The lamp's an ELC - came with the Chromega color head. Film with the Color Checker frame is Portra VC-160, 120 size. I also shot a roll of UC-400, but haven't made a print from it yet. I did make contact sheets of both rolls, and color balance looks good on both.

Unusual is right. I've never run into anything like this.

 

[Photo Engineer]

Ed, I would like to address your comment about cyan filtration.

Since color negative paper has no blue light absorbing layer, and the yellow layer is on the bottom with cyan on top, there is a virtual requirement that filtration be on the red (m + y) axis only with no cyan. If you go to the cyan side, you are apt to get bad color contamination among other things due to crosstalk by blue light.

This will result in greenish cyans, and reddish magentas for starters.

So, when I see cyan filtration with negatives, I troubleshoot the entire system as something is seriously wrong and will lead to bad prints. As you say, there is no law that says this cannot happen, but when it does it seems that something is wrong and should be fixed for optimum performance.

PE

 

[Dave Starr]

Ed, I would like to address your comment about cyan filtration.


So, when I see cyan filtration with negatives, I troubleshoot the entire system as something is seriously wrong and will lead to bad prints. As you say, there is no law that says this cannot happen, but when it does it seems that something is wrong and should be fixed for optimum performance.

PE

That's why I'm not going to use Fuji paper when the box in question is gone. I'm a lot more comfortable using the 45M 80Y I need with Supra papers.

 

[eumenius]

Cyan filtration is not an unusual thing for me - but I don't usually use more than C20, and only in case when I need to re-balance the whole pack (if I have to remove, say, Y20, but Y is already 0). In such case I add C20, M20, and Y0. But, honestly, my numerical data shouldn't be taken as a last instance - the numbers refer to an old Magnifax II with Janpol Color 80/5.6 lens, and an Osram Halolux 150W household opal halogen lamp. To print Fuji NPL 160 on that system (Kodak Endura Supra paper, F surface) I have to switch on the whole magenta available (M100), with no yellow filters at all. NPS requires some yellow, as well as Agfa Optima - but not too much. The colors, though, are dead on as a result of all tweaking

Old Janpol showed itself from a good side - I didn't expect it would work at all, but the prints' sharpness and colour are quite OK with it. I didn't try to print 135 film with it, because I prefer minilab for such things

Zhenya

 

[Ed Sukach]

Since color negative paper has no blue light absorbing layer, and the yellow layer is on the bottom with cyan on top, there is a virtual requirement that filtration be on the red (m + y) axis only with no cyan. If you go to the cyan side, you are apt to get bad color contamination among other things due to crosstalk by blue light.

And now to explain, in not more than 10 words...
Not a place where I want to be.

If one starts to "balance" the light from the Dichroic Color Head, one will occasionally "run out of room" (usually because of a great mismatch of film-to-ambient light source temperatures). As an example, to obtain balance, with a certain negative, the amount of yellow filtration will be too great, and cannot be corrected, even when the yellow fitration is reduced to zero.
What is then necessary is the introduction of "cyan filtration" to change the starting point of the filter pack. If 20cc of cyan is introduced, the actual value of "yellow" will be increased to +20cc, and will allow further reduction (magenta will be also affected to the same intensity, +20cc more than before). That is why there is a cyan filter.

THis is one of those things that are far easier to understand in practice, than it is to describe it in writing.

... Almost missed this.... There is, most certainly a "blue sensitive layer" in Color paper. An example from the data sheet for Agfa Signum:

"Emulsion structure:

The light-sensitive emulsion consists of silver chloride crystals imbedded in gelatine. The red-sensitive layer contains the cyan component, the green-sensitive layer the magenta component, and the blue-sensitive layer the yellow component."

 

[Photo Engineer]

Ed, the blue sensitive (yellow dye forming layer) is different than the blue light absorbing layer present in films but not in papers. The blue sensitive layer is on top in films followed by a yellow dye layer to absorb blue light and prevent punch through of blue light into the underlying layers.

In paper, the yellow dye layer (blue sensitive) is on the bottom therefore preventing the inclusion of a blue light absorbing layer. All layers in paper have blue sensitivity and must rely on speed differential for separation of color and prevention of color cross contamination. This requires that the blue speed of the yellow layer be much higher than red speed of the cyan layer and the use of yellow filtration to reduce the blue speed of the blue layer down to equal the red speed. At the same time, it reduces the blue speed of the red layer to effectively zero thereby eliminating crosstalk. Average blue layer grain size in papers is about 2 microns and for the red layer is about 0.2 microns, a factor of 10x reflected in their raw speeds of both to blue light.

Moreover, adding cyan filtration using a good cyan filter, should have little effect on the yellow component (or blue light) in the beam of light. If it does, then you have a bad cyan filter with lots of crosstalk. Even with 'bad' cyan filters, a change of 10 or 20 Cyan should be only about 5 yellow or less.

Paper structure

C/IL/M/IL/Y/Support

Film structure

Y/Yellow dye IL/M/IL/C/Support

Film speed for tungsten C<M<Y proportional to tungsten emission. This yields a neutral to the tungsten light.

Film speed for daylight C=M=Y (approximate) to daylight 'neutral white' emission. This yields a neutral to daylight.

Film speed for paper C<M<Y proportional to tungsten illumination + dmin of film + ~50R. This requires a piece of film and about 50R to achieve a neutral to average tungsten enlarger lamps.

PE

 

[Ed Sukach]

Ed, the blue sensitive (yellow dye forming layer) is different than the blue light absorbing layer present in films but not in papers. The blue sensitive layer is on top in films followed by a yellow dye layer to absorb blue light and prevent punch through of blue light into the underlying layers.

All very interesting, and I'm going to cut some slack here. Generally true, but in Film there is a yellow filter layer immediately below the blue sensitive and UV filter layers. That yellow filter is not present between the green and red sensitive layers... and introduces a Yellow BIAS that is usually sufficient to eliminate the need for cyan filtration in printing.

Be that as it may, I commented on the statement, "Color negative paper has no blue sensitive layer" (not true) - not that the structure of color film and paper emulsions were "the same".

Interesting - It has been some time since I've delved through my collection of Data Sheets - the first book that I came upon was Agfa. Apparently they balance all their color paper to produce a neutral grey - equal parts of red, green and blue - when exposed to the light emitted, unfiltered, from an enlarger lamp with a color temperature of ~ 3000K. An enlarger with a lamp emitting a different color temperature will, necessarily require different filtration.

 

[Photo Engineer]

Ed, sorry but I never said what is reflected in this quote from your last post.

"Be that as it may, I commented on the statement, "Color negative paper has no blue sensitive layer" (not true) - not that the structure of color film and paper emulsions were "the same". "

I actually said "Since color negative paper has no blue light absorbing layer, and the yellow layer is on the bottom with cyan on top" so there seems to be some misunderstanding here.

Also, Agfa may do as you say here;

"Interesting - It has been some time since I've delved through my collection of Data Sheets - the first book that I came upon was Agfa. Apparently they balance all their color paper to produce a neutral grey - equal parts of red, green and blue - when exposed to the light emitted, unfiltered, from an enlarger lamp with a color temperature of ~ 3000K. An enlarger with a lamp emitting a different color temperature will, necessarily require different filtration."

But this merely gives an approximation without taking into effect the masking of the color negative. This is done by including an average dmin bias. In addition, this does not account for how the manufacturers balance for the average population of color negative materials they make. In fact, please take note of the fact that the current Endura papers has increased green speed (and a higher basic magenta filtration) by about 15M compared to the Supra family of papers which I found stable over 10 years. This was not done without a reason.

In the end, this is why each color paper manufactured out there has a slightly different basic response pattern and each color negative film has a different basic balance when printed. The photofinisher must take these into account as well as the home darkroom worker. Some papers respond better across all film types than others and this is related to the speed relationships of the blue and green sensitive layers (red being taken as the zero point) and the spectral sensitivities of the papers themsleves.

PE

 

[Ed Sukach]

Photo Engineer,
There seems to be something of a "shifting sea" in this exchange. If I discuss one aspect of color papers/ printing, something is introduced to deflect specificity to that particular subject.

Photo Engineer,
Going back to the original "set", I'll make a few SIMPLE statements:

1 (a). Color Negative film is commonly structured with three light-sensitive layers: red-sensitive, producing a cyan image; green sensitive, producing a magenta image; and blue sensitive, producing a yellow image - ALL on a single "negative" base.
This is not all-inclusive - there are other layers for various purpose - nor necessarily in any order.

1 (b). Color Paper (I have to be careful here) for use in making "positive" images from negatives, is commonly structured with three light-sensitive layers: cyan sensitive, producing a red image; magenta sensitive, producing a green image; and blue sensitive, producing a yellow image. Again, in no particular order, and other layers may be employed for various purposes.

2. In my experience, USUALLY only two dichroic filters are necessary in color printing: magenta and yellow. Occasionally more filtration is required, making the use of the cyan filtration necessary. By FAR the most common reason for cyan filtration is the mis-match between the source of illumination and the film color balance (Daylight, Tungsten, Type A, etc.), rather than some anomaly in the processing.

Now... I may be dense, but one thing you have written makes NO sense to me, from any point that I read it:

"Film speed for tungsten C<M<Y proportional to tungsten emission. This yields a neutral to tungsten light.

Film speed for daylight C=M=Y (approximate) to daylight 'neutral white' emission. This yields a neutral to daylight."

I'm not at all clear of what is happening here - C(yan) is less than M(agenta) is less than Y(ellow) and therefore something suitable for tungsten illumination (??), and C(yan) equal to M(agenta) equal to Y(ellow) is therefore suitable for daylight??? What is the significance of "equal to" and "less than"?

I am even more lost in the, "Film speed for paper (should this be "paper speed" or "exposure sensitivity?) C<M<Y proportional to tungsten illumination + dmin of film + ~50R. This requires a piece of film (?) and about 50R to achieve a neutral to tungsten enlarger lamps.

A "piece of film"? - ANY film?

 

[Photo Engineer]

Ed, tungsten illumination is rich in the red region of the spectrum, less so in green and even less so in blue. Therefore, to achieve a so called neutral with nothing else intervening, the red speed is slower than green which is slower than blue. The blue speed must be fastest to make up for the low blue emission of tungsten illumination.

This is good, because color negative papers have no yellow absorbing layer to protect the cyan and magenta layers from punch through of blue light. You see the cyan and magenta (red and green sensitive) layers are sensitve to blue light as well as to their primary region of the spectrum (red and green of course). But, since there is still a bit of punch through possible, the blue and green speeds are jacked up by the amount of speed equal to the punch through (about 50R worth) so that the filters in the beam remove the last residual element of punch through by knocking back this excess speed.

In addition, since a color negative is going to be printed, and it has an orange mask, that amount of extra speed must be added to the blue and gree layers to offset the mask. (you can observe this by contact printing a perfectly balanced negative - you will see that the border of the negative reproduces as a light gray due to this effect.)

In actual fact, the fundamental speed of color negative papers is judged by the speed of the cyan layer and the other layers are adjusted upwards from that point to achieve the goals above, namely 1. Approximate neutral from tungsten light, 2. +50R to remove any vestige of punch through, and 3. B and G speed bias approximaely equal to the dmin mask of average color negative film.

In practice, the Cyan (red sensitive) emulsion therefore uses a 0.1 - 0.2 micron grain and the Yellow (blue sensitive) emulsion uses a 1.0 - 2.0 micron grain that is nearly film speed. Since we distinguish yellow detail poorly, the grain caused by this size difference is not easily seen.

To see these effects, look at the wedge spectrograms of color paper published on the Kodak web site. The last time I looked, it clearly showed the Cyan and Magenta contamination of the Yellow due to punch through that is eliminated by appropriate filtration. If this is not done (ie by using cyan filtration) then this punch through can begin to show up in your prints. As you say, there are many reasons that one might need cyan filtration, but this does not mean it is what was intended by the manufacturere for optimum results.

So, the piece of film is a piece of negative color film, processed but unexposed.

PE

 

[Ed Sukach]

Ed, tungsten illumination is rich in the red region of the spectrum, less so in green and even less so in blue.

Please! There is no need to describe the spectrum form a tungsten lamp. I've done a fair amount of color spectrophotometry.

So, the piece of film is a piece of negative color film, processed but unexposed.

It would have helped to know that what you were talking about was the sensitivity to given wavelengths of light in the various layers.

However, If the C<M<Y applies to emulsion layer speed, are you saying that C=M=Y indicates that all layers have the SAME sensitivity to daylight illumination?

Also, Is Agfa's claim that exposure to naked enlarging lamp emission of 3000K - No filtration or "film" attenuation - resulting in equal exposure of all layers incorrect or --- ???

 

[Photo Engineer]

Ed, the C=M=Y applies only to daylight film, assuming equal energy distribution. (Of course sunlight peaks in the green region at about 530 nm (I just have an approximate figure there) and so there is a slight discrepancy in actual practice).

As for Agfa or any other color paper manufacturer, I would assume that either they are correct for their paper, or it is a simplification. To print well from the current population of color negatives, the ordering I described is a virtual requirement in order to avoid color contamination.

The alternative places the yellow layer on top, and adds a yellow filter dye layer, thereby sacrificing dye stability and still begs the issue of printing with tungsten illumination and orange masked negatives. So, in the final analysis, the ordering of color negative paper speeds is C<M<Y to achieve all of the stated goals.

This could concievably be done with a starting filter pack of zero (0,0,0), but then printing would be ever so much more difficult requiring a lot of calulation and zeroing out of neutral densities in the filter packs. So, all manufacturers have apparently done it the way I describe and you can add the goal of simplifying the printing step by only requiring 2 filters (M and Y).

PE