C-41 alternative chemistry

[mts]

As discussed for components, namely bleach, there are alternatives to kit or "official" C-41 chemistry. I am attaching a test image as example.

The image is a direct scan (Nikon LS-3500) of a small portion (about 1/8 frame) of an image taken of the MacBeth chart and an 18% grey scale card. Processing was done using entirely scratch-mix alternative chemistry. Bleach was Fe-Ammonium EDTA. The particulars for this image are:

Minolta 7000/50 mm f/1.7 lens
illumination direct sunlight (6800' elevation)
ASA-160
Portra NC
~1/8 frame scanned at 300 dpi/scaled and converted to .jpg attachment
no scanning color corrections are applied

Perhaps others would like to provide examples for discussion?

[Photo Engineer]

Considering the manipulation of the scanning process itself, turning a negative into a positive, we then have to consider the results from various scanners.

Here is Portra 160VC in authentic C-41 chemistry. It was shot at ISO 160, on 120 film in an RZ67 with auto metering.

I edited this to include a larger version.

PE

[mts]

Thanks for the post. Mine is fuzzy because I scanned only a small portion of the negative, let the camera autofocus, and the scanner is probably not optimally focused. Unfortunately there is no alternative to scanning for creating images for web-posting, so like it or not we have to interface to the digital world at least a little. The LS-3500 is a bit on the crude size with regards to focus using film holders of differing thicknesses. On the other hand, the image processing that this scanner does is minimal and much of it can be set by the user.

I have a project on my back burner to write new scanner software for this unit intending to expose some of the internal manipulations to the application program. I'll leave that subject to the apug sister forums.

[Photo Engineer]

Here are the proof prints on Endura Supra.

I exposed these at f11, f5.6 and f16 respectively to emphasize the different speeds of the film used.

The range is ISO 25, 50, 100, 200, 400 and 800 with the reference posted above at 160 shown at the top as a single photo. The correct exposure for this film is the ISO 160 with the print at f11. It reproduces a lot zippier on the paper than it does in a direct scan.

Contrast and brightness manipulation would make the scan match the print. IDK how yours would print due to this type of problem. As you say, scans are all we can rely on.

PE

[dmr]

Processing was done using entirely scratch-mix alternative chemistry.

Out of curiosity, did you use Kodak's CD4 or a commercial alternative, or did you compound your own?

Just curious.

[mts]

I use CD-3 and CD-4 from third-party suppliers, the last I believe purchased from Photog. Formulary. Ultimately it probably came out of a Kodak plant, or these days likely from a chemical factory in India. I got my Dimezone-S stock from India a couple of years ago after waiting months for it to finally get to Long Beach by way of bannana boat. Then it was stuck in customs for another month, but finally showed up in a UPS package on my doorstep.

[mts]

It's amazing how good Kodak films and the other current emulsions really are. The Portra 160NC image I posted required only a minor color correction whereas the recent test attached here took more correction and does not have the nice parallel characteristic curves of the new emulsions. That is to say there is a bit of cross-over in the toe and shoulder, but some of that could be attributed to the fact that the film sat in my freezer for a good ten years or more. This example is Fuji Super G-100 that I got really cheap in a 100' roll from FreeStyle a long time ago. It was processed in the same chemistry as the Portra 160NC example I posted earlier.

The grain is much more noticeable and under magnification the color layers are not nearly as uniform as in the modern films. Still, the colors are there and the processed film produces acceptable prints, although nothing that you would like to enlarge very much beyond say 5x7" size.

[Photo Engineer]

Well, another factor is that all C-41 films are supposed to react to C-41 identically as much as is possible to all parameters, but this is not true for home-made developers.

So, I have seen cases where two films are identical in Kodak and Fuji chemistry, but only one of them "works" in a home made developer.

I once ran a similar experiment with several coatings of color developer and 12 different developer formulas. The papers were all the same in the genuine Kodak color developer, but each paper gave vastly different results, similar to the problems you saw above, in the other developers. However, one paper was correct in at least one of the other developers.

Perhaps this is what you are seeing here. It is can be due to emulsion thickness, coupler types, correction chemistry, and Iodide content in the emulsions. All of these cause varying reactions to the chemistry.

I would like to add that I discussed this a lot with Pat Dignan many years ago.

PE

[mts]

Having some insight into photochemistry history is valuable and worthwhile to archive in the apug forums. Pat Dignan was a real proponent and supporter of do-it-yourself amateurs and has been long missed. Dr. Robert Chapman (in Photo Techniques) used to champion a method--I have forgotten the technique's name--to run tests for many different variables, for example through variations in the chemistry components for alternative C-41. Somewhere in all these variables there might (or might not be) a combination that works well. I still think a lot of my result above is explained by simply comparing apples (new current emulsions) with oranges (old ones from previous film generations). There is a shadow cast on the gray card in the Fuji example above and in it you can see some of the cross-over effect I mentioned. On the other hand, white snow looks pretty decent as do the RGB and CYM patches.

I have yet to try any Ektar 100 but look forward to so doing. Next I think I will try something that works well (Portra 160NC) in some of the other bleach formulae to see just how much difference is actually present.

[Photo Engineer]

The technique you mention is called a factorial and you use statistical analysis to examine your data. I did not agree with a lot of Chapman's writings, as he had missed a lot of information. Pat Dignan and I discussed his use of CD-4 in rapid access print processing. I pointed out to him that there would be a severe loss in dye stability and I knew that simply because I had run a large "factorial" experiment on developing agent vs coupler for the patent for CD-6.

Now, as for the results above, my point is that all films of the C-41 family should behave alike in a "real" C-41 developer. If they do not, for any reason, then the developer is wroing. Since all films are released to have no crossover, then an ISO 160 and an ISO 800 film, tested as above should give no crossover and really should behave alike to push and pull. This result should be the same across manufacturers, as they release film to the same standard.

PE