There is a lot of conjecture and skepticism out there regarding the stability and efficacy of "hobby" type chemistry kits, especially when it comes to slide processing. Kodak Ektachrome E100 with an Olympus Zuiko 50mm at f/2 bracketed 1 stop over and under. All frames were scanned on the Skier Sunray Box with a Canon 5D mk2 with all the same settings and corrections. The Darkroom specializes in professional film developing and scanning. Their Sitte Tischer TruTrak dip & dunk processor maintains high professional standards with constant process control standards. The remaining film was sent to The Darkroom photo lab and processed with the 6-bath E-6 process. Snip tests were made and processed in each of our three 1st developers at 104ºf and the remaining 2 Cs6 baths at ~85-100ºf in a Patterson tank. Just see for yourself! We bracketed exposures of an extreme lighting situation just before sunset, with cool skylight and warm backlight. The reality is that there are no compromises between fresh Cs6 and carefully replenished E-6 chemistry. People often wonder, "What are the compromises with combined processing baths?", such as the Cr6 "Color&Reversal" 2-In-1 Slide Solution or the Bf6 "Bleaches&Fixer" 3-In-1 Slide Solution. The reversal step occurs during color development in a Color&Reversal bath, and the pre-bleach, bleach steps are combined with the fixing step in a Bleaches&Fixer bath. Looking back over my C-41 control strip data, it does look like the R and B channels are always the most widely separated in both the HD and LD patches, so perhaps this always holds true? In any case, if anyone has experience doing E-6 process control, I'd greatly appreciate some clarification on how the color spread is calculated.With the Cs6 "Creative Slide" process the number of processing baths for E-6 film is reduced from 6 to 3. This is sort of consistent with the Kodak definition given above, except that Kodak doesn't assume (like the Alvandi document) that the density values for the R and B channels will always be the farthest apart. The author of the Alvandi document goes on to define "spread" as the value calculated from for each of the LD and HD patches. Through this kind of calculation the control values for green are established to equal zero and thus become the reference point for the deviation (R - G) and (B - G)." The difference of red minus green (R - G) and blue minus green (B - G) are obtained for both steps by mathematical calculation. The control values obtained in the color control step (HD) and the sensitivity control step (LD) are the basis for this calculation. The necessary values, however, can easily be calculated from the existing data. "An existing deviation in color balance, unlike directly measured density deviations, cannot immediately be seen from the values obtained through the measurements. The color-balance spread limits for LD and HD are given in Table 13-1."Īnd here's how the Alvandi Systems E-6 Process Manual (section 2.4.8) defines it: If your process exceeds the color-balance spread limit, stop processing customer film and take corrective action. "Color-Balance Spread Limits: A color spread is the density difference between the two most widely separated color plots of the LD and HD steps. In E-6, however, it appears that color spread is defined differently and is two values instead of one (i.e., one value for the HD patch and one value for the LD patch). Once found, that single value is compared to the spread that was similarly calculated for the corrected reference strip, and the difference between the two determines to what degree your process is in control. In C-41 process monitoring, "color spread" is a single number, which is determined by first calculating HD - LD for each of the three color channels (e.g., R HD - R LD, G HD - G LD, and B HD - B LD), then finding the density difference ("spread") between whichever two channels are the farthest apart in those three calculations. What I'm confused about is how to calculate the color spread in the LD and HD patches (parameters 5 and 6, above). Parameters 1-4 are pretty straight forward. difference in D-min (i.e., control strip RGB density values - corrected reference strip RGB density values).The info on E-6 process control is somewhat scant, but from what I've gleaned from Chapter 13 of Kodak Z-119, there are six parameters I need to measure: I've been running Fuji-made C-41 control strips with my Kodak Flexicolor chemistry with success and would like to start monitoring the quality of my E-6 chemistry using Fuji's E-6 control strips.
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