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I just developed some C-41 negatives the other day, and previewed them with my phone on negative image mode. All the images have a fairly strong cyan cast. Looking online at other negatives people have uploaded, this seems to be very common. How were prints made of this film type (I understand the concept of enlarging and photo paper) with the cyan cast absent? When I say original I mean the pre-digital method. I would prefer to stay away from digital processing, as I do not own a film scanner and all my flatbed scanners create low resolution​ scans.

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How was the cyan cast of C-41 negatives originally removed?

By applying color correction filters during the enlarging/printing process. Normally a strong yellow filter and a more moderate magenta filter were used. Other ratios between the yellow and magenta filters were used for color correction. For example, if tungsten film was shot in daylight it would need an even stronger yellow and magenta filter.

  • Reminds me of the original RIAA audio curve for LPs. – Carl Witthoft Jun 7 '17 at 11:37
  • Except the exact tint of each type of film is not standardized. One might need to filter slightly differently for Kodak color film compared to Fuji color film. – Michael C Jun 7 '17 at 22:04
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The C-41 negative film process arose from movie film that was marketed just after World War II. Previously, processing color films was a far more arduous task.

To simplify, three dyes, cyan (blue-green), magenta (red-blue), and yellow are incorporated into the film during manufacture. The dyes in this film is incomplete. The three dyes are all missing the same ingredient. That ingredient is in the developer solution. The developer is rather common black & white formula plus the missing ingredient.

As the film is developing, metallic silver forms in the exposed regions. Dissolved oxygen in the waters of the developer rapidly oxidize the surface of this newly formed silver. The action is the catalyst that causes the dyes to unite with the missing ingredient. Now the dyes blossom and a color image forms.

The problem is, the cyan dye is not the correct color. The magenta dye is good but could be improved. The yellow dye is worthy. The industry never was able to find better cyan and magenta dye that would fill this bill, i.e. one missing ingredient that is needed to simplify the developing process. For example, Kodachrome required three separate developer baths.

How to bolster the poor cyan and magenta that must be used? The undeveloped cyan dye was tinted red. The undeveloped magenta dye was also tinted. Together they appear orange. As they developed the orange tint is lost, but not in the unexposed areas. Thus the orange “mask” markup is actually two positive image superimposed atop the three negative dye images. Thus the image is comprised of 5 dyes.This positive orange mask corrects the off frequency cyan and magenta dyes. It’s complicated to make this film but easy to develop. The finished product yield pleasing prints.

The key here is “prints”. The printing paper consist of three emulsion layers, one for the red exposure, one for the green exposure, and one for the blue exposure. The emulsion speeds are not equal. The paper speeds are adjusted so that the red emulsion needs less exposure. The green and blue emulsion will be over-exposed unless these light energies are mitigated. Magenta filters to mitigate the green light exposure and yellow filters to mitigate the blue exposing light are deployed during the printing exposure. The red exposure is controlled only by the lens aperture and the time of the exposure. The bottom line is, the color balance of the finished print is controlled by adjusting the amount of yellow and magenta filters. In this way the exposing light is custom adjusted for a good color balance.

Typically, the color balancing filters used will be heavy on the amount of yellow filters and moderate on the amount of magenta filters. If the resulting print is off-color, the ratio of yellow to magenta filters is altered and this color corrects the final print.

  • How would I accomplish this? Would I use color filters and expose to the print paper for separate exposure times? – ToastHouse Jun 7 '17 at 0:31
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    We print using an enlarger that accommodates cyan - magenta - yellow filters in adjustable densities. Typically, the starting filter settings are 0 cyan - 40 magenta and 80 yellow. After a print is made, the color balance is evaluated and the filters are adjusted. If the print is too yellow, we add yellow filters. If too blue, we reduce the yellow filter amount. If too green we reduce magenta filters. if too red we add magenta and yellow in equal amounts. If too cyan we reduce magenta and yellow in equal amounts. Each negative will likely require a different filter setting. – Alan Marcus Jun 7 '17 at 0:40
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    The additive method is three exposures to the paper. One with a strong red filter, one with a strong blue filter and one with a strong green filter. The final print is adjusted by changing the exposure times of each. This is the more difficult method. Best is the subtractive system using a white light enlarger and magenta and yellow filters to adjust final color balance. – Alan Marcus Jun 7 '17 at 0:47
  • Excellent answer. It reminds me why I stick to the (comparatively) simpler black 'n white printing :) – Jindra Lacko Jun 8 '17 at 18:39
  • @ Jindra Lacko -- Thanks -- For many years I was an instructor Professional Photographers of America School Continuing Education - Subject Color Print and Process. – Alan Marcus Jun 8 '17 at 20:21

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