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  1. #1
    Greg Davis's Avatar
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    C-41/RA-4 and alternative process comparison

    A few months ago an alternative process was posted with claims that it was good for a direct replacement for the standard C-41 film and RA-4 print processes. I wanted to test these alternatives against the standard processes and see what the results would look like. To outline my testing process, I did the following:

    Shot 2 sheets of Kodak Portra 400 film and processed one each in both film process formulas, then printed both negatives using both print processes. Both were done using published instructions and a Jobo CPA-2 machine for consistent temperature control and agitation. To confirm my visual test, I also processed standard Process Control Strips for both C-41 and RA-4 using all methods for densitometric comparison. The results of the strips were plotted on Kodak Y-55 control graph forms and presented here. Lastly, I scanned all the control strips and negatives so a visual comparison can be made side-by-side with the reference strips that come packaged with the control strips. All prints were balanced for the grey card to demonstrate color and contrast differences in relation to the standardized card.

    To outline the processes:

    The C-41 process used is the published Kodak process using standard Kodak C-41 Developer, Bleach, Fix, and stabilizer. The steps are as follows:

    @100° F (37.7° C)
    30 second water pre-rinse
    3:15 minute development
    6:30 minute bleach
    5 minute running water rinse
    6:30 minute fix
    10 minute running water wash
    1 minute final rinse
    dry

    The RA-4 process used is from the Kodak Color Darkroom Dataguide (R-19) for rotary tubes using Kodak RA-4 RT Developer/Replenisher and Blix as follows:

    @83° F (28.3°C)
    30 second water pre-rinse
    2 minute development
    2 minute blix
    5 minute running water rinse
    dry

    The alternative film process is as follows:

    @100° F (37.7°C)
    12 minutes Kodak RA-4 RT Developer/Replenisher 1+4
    30 second acetic acid stop (18mL/liter 28% acetic acid)
    4 minute Kodak Rapid Fixer 1+3
    30 seconds Potassium Ferricyanide Bleach (50 grams/liter)
    30 seconds re-fix
    5 minute running water wash
    30 second rinse in water with 2 drops of dish soap
    dry

    The alternative print process is as follows:

    @83° F (28.3°C)
    2 minutes Kodak RA-4 RT Developer/Replenisher 1+4
    30 seconds acetic acid stop bath
    4 minutes Kodak Rapid Fixer 1+3
    30 seconds Potassium Ferricyanide Bleach (10 grams/liter)
    30 seconds re-fix
    5 minute running water wash
    dry

    Note that I shot a roll of Kodak Ektar 100 as well, but I did not print them.
    I also ran RA-4 control strips at differing temperatures and times using both starter and without for a different test, but I thought they may of interest here. The charts show the plot points for each control strip as labelled by column. For those that have not seen one of these charts, they are not normally organized this way, but hopefully you can decipher the results. The point is to get the three colors to plot in between the red and black lines for each of the four categories. The lines show the progression from one control strip to the next.

    Here are the results:
    Attached Thumbnails Attached Thumbnails C-41 comparison Portra.jpg   C-41 comparison Ektar.jpg   RA-4 comparison.jpg   Y-55 C-41.jpg   Y-55 RA-4.jpg  

    RA-4 Control Strip 01.jpg   RA-4 Control Strip 02.jpg   RA-4 Control Strip 03.jpg   RA-4 Control Strip 04.jpg   RA-4 Control Strip 05.jpg  

    RA-4 Control Strip 06.jpg   RA-4 Control Strip 07.jpg   RA-4 Control Strip 08.jpg  
    Last edited by Greg Davis; 05-08-2012 at 02:57 PM. Click to view previous post history.
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  2. #2
    Greg Davis's Avatar
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    The RA-4 Control Strips show that the print process (with starter included) plot within aim and control at 83, 88, and 94 degrees F, the rest do not. The alternative process plots within aim and control, but the yellow patch shows significant retained silver due to the incorrect bleach and fix steps used.

    The base of the film shows a marked staining toward green and brown in the alternate process when visually compared to the film base of the C-41 processed films. Ektar showed significantly more staining than the Portra. The increased contrast in the negatives are most likely due to the extended development times, which were, quite frankly, a guess since it is not a standard process.

    From what I can see in the prints themselves is a slight crossover in the alternate print made from the C-41 negative giving her skin a slightly yellowish color while making the shadows a little more blue, though not much. It was the correct developer, just more dilute, the retained silver did not have much effect in contrast, but that may be why her skin is off rather than crossover. The alternate film process, however, shows significant color crossover in the blue layer. Her skin is strongly yellow in comparison and the shadows get much more blue as evidenced in the utility meter in the bottom right corner. Saturation is also slightly lower, even with the higher contrast. The shadows in the brick in the upper left corner also get more blue. If I correct for the blue shadows, I get a much more yellow neutral card and skin tone. The alternate negative and print combination compound the issues even more. Looking at the Y-55 plot points for the film, you can clearly see the blue layer charting way off the reservation.
    www.gregorytdavis.com

    Did millions of people suddenly disappear? This may have an answer.

    "No one knows that day or hour, not even the angels in heaven, nor the Son, but only the Father." -Matthew 24:36

  3. #3
    hrst's Avatar
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    Thanks for this really interesting test and putting so much effort on just to show us this.

    This hopefully puts end to "developing C-41 in my urine and hair dye gives perfect results every time" myths, combined with the earlier results that lowering the temperature too much really causes crossover and loss of saturation.

    On the other hand, this test also shows that crudely wrong processes can give perfectly USABLE results (at least for some people); results that look like color pictures, with some unwanted casts but nothing too serious when the content matters more, or when some unexpected color errors are wanted. The much longer shelf-life of RA-4 developer is a really good argument for this process.

    I once accidentally diluted C-41 developer 1+1 by forgetting to drain prewet. At that point, I extended the time somewhat but forgot how much. The result had quite a large color shift that needed filtration not normally used, but when applied, the crossover or other problems were not that evident in "normal" pictures without any side-to-side comparison available.

    But, color paper is really a different beast, much more robust. Also, if we suppose that the yellow patch looks odd due to retained silver, then diluting developer 1:4 doesn't seem to have too much effect. However, I'm a bit surprised the ferricyanide bleach did not work that well. I've used it on RA-4 paper with good results. My recipe was 40 g/l ferricyanide, 25 g/l NaBr and bleaching time of around 2 minutes, with very good washes both before and after. Maybe the one you tried is too dilute, lacking bromide or time too short. Also, I don't understand the reason for two-step fixing, especially as the latter step is very short and the first much longer than would be necessary. But then, I understand this is not your process but something random from the internet. Maybe the penny-pitching has just gone too far ? Diluting everything down is not cost saving because you can reuse it less and less, and the process times go up, or the chemicals don't do what they are supposed to, as shown here. OTOH, use strong enough ferri bleach with the correct recipe including bromide, and you can probably reuse it very long and have real savings.

    I still don't understand why I should dilute my RA-4 developer. It seems to have practically infinite shelf life as is and it processes an enormous amount of prints per liter. This amount probably goes down with dilution, although it's probably still quite much. Think about dividing infinite by four .

    What was not tested was possible dye stability (long-term fading) issues with "alternative C-41" due to the use of wrong developing agent. If it also causes dye hue (absorption spectrum) issues, then the resulting film may "respond" differently to different post-processes (subtractive printing, additive printing, densitometer, different scanners) than normally developed films would. So, even if the hue errors are ok, I wouldn't process any important to-be-archived work like this because of the risk of it fading later on...
    Last edited by hrst; 05-08-2012 at 08:59 PM. Click to view previous post history.

  4. #4
    Greg Davis's Avatar
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    I am all for experimenting and trying new things just to try them. The process I tested is a perfectly valid way of making photographs, as long as color fidelity is not expected. But I think if one is going to screw up the colors, they may as well go whole hog and cross process.

    I expect the refixing is to eliminate the silver salts created by the bleach step after the original silver salts were fixed out.
    www.gregorytdavis.com

    Did millions of people suddenly disappear? This may have an answer.

    "No one knows that day or hour, not even the angels in heaven, nor the Son, but only the Father." -Matthew 24:36

  5. #5
    hrst's Avatar
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    Quote Originally Posted by Greg Davis View Post
    I am all for experimenting and trying new things just to try them. The process I tested is a perfectly valid way of making photographs, as long as color fidelity is not expected. But I think if one is going to screw up the colors, they may as well go whole hog and cross process.
    Totally agree!

    I expect the refixing is to eliminate the silver salts created by the bleach step after the original silver salts were fixed out.
    Yeah, of course, but I was thinking of eliminating the first step, as the second one does it all. So instead of 4 minutes + 30 seconds, just 2 minutes at the end would do the job.

  6. #6
    Greg Davis's Avatar
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    I cannot answer that, I was just following the instructions.
    www.gregorytdavis.com

    Did millions of people suddenly disappear? This may have an answer.

    "No one knows that day or hour, not even the angels in heaven, nor the Son, but only the Father." -Matthew 24:36



 

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