How commercial color film processing machines do it.

mgonzale

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I was in my local camera shop recently and asked if they ever carried chemicals to do E-6 at home. I've been reading about experiences here in doing E-6 at home, looking for whether it's hard/easy, consistent or not, expensive or not and all that. The salesman said that one reason he doesn't carry it is that it's not consistent enough for most people. And the reason he cited was that some processing machines (used to?) precisely flash the film with light as part of the process. Of course, a chemical kit is just chemicals and is a compromise for the sake of not having the flashing step available to us folk in our homes. I've read quite a lot here on the achievable results with E-6 at home, so my question is mostly just a curious one about those machines flashing the film. Is this true for older or current commercial processing machines?
 

Volvospeed

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Not sure what he was thinking but E6 is the film process. There is no light or chemical flash involved. Its going to be either a 6 bath or 3 bath kit.


I am working on a how to for http://volvospeed.com as we speak. The overall process is very easy assuming you have a way to control the temperature of the water. If you have a Jobo, fujimoto, or whatever it is easier but they are not needed. I process at 38C and use a Wing Lynch for the water contol. If you are using a jobo you can get an external tank and heater instead if you wish. The key is just figuring out the film you are using. I shoot Provia only which I always push 15%. As for price Adaroma sells a one shot 5L kit for about 55 shipped. A roll of 120 takes ~175ml and 4 4x5s takes about 250ml. So ignoring the equipment you are looking at about 2.50 per roll of film or 4 sheets.
 

Removed Account

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I'm pretty certain that the E-6 process uses a chemical fogger rather than flashing. Kodachrome uses flashing, but I don't know about other reversal processes.

- Justin
 

Nick Zentena

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The bottle labeled "reversal" is the bottle of light. Isn't it?

If you check the web sites on B&W slides you'll often see bits about using light instead of chemicals. I don't think this is the tough step.
 

Volvospeed

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Its not tough but its also not needed IMHO. Using the Jobo2500 and ATL1000 for smaller jobs I have never had a problem with consistent results as long as water temp was held stable. Density, saturation, contrast and general are results were always fine. Just stay away from the 3 bath kits.
 

fschifano

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Years ago I did some Anscochrome processing. The process required you to re-expose the film to light part way through the process. Perhaps one of the old Ektachrome processes required it as well. Modern E-6 processing uses a chemical fogging agent, obviating the need for re-exposure.
 

David A. Goldfarb

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In reversal processing that involves exposure to light, my impression is that the film is usually fogged completely, so that as long as a certain minimum exposure is achieved, the time isn't critical. For Kodachrome there are three different exposures, so I'm sure it's more complicated.
 

pwitkop

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As far as I understand (and there are plenty here who know much better than I do), there is never any light used in E6 processing, it uses a chemical reversl instead. Chemical reversal produces better (cleaner) reversal than re-exposure, both options can be done in B&W reversal processing. IIRC, Kodachrome required exposure to specific colored light during processing, could this be where the sales persons confusion came from?

Peter
 
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mgonzale

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Thank you for the answers you've given. It's possible from my simple questions in the store that he knew what he was talking about and chose to talk about more than E6 color but didn't want to get into the details. I got there 5 minutes before closing and the lights were already dimmed when I walked in. I'm still warming up to doing color processing at home. I've got a Jobo 3006 drum on a motor base that I'm putting through the paces with B&W 4x5. Maybe I'll get a temp-controlled water bath going and try C-41 or E6 in the coming months.
 

Michael W

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I think it was the E4 process that required exposure to light to reverse the image. I know a guy who used to do it & that's what he told me. E6 does it all with chemistry as noted by others. I think that's one reason why E6 became so popular.
 

PHOTOTONE

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It was the E-2 and E3 processes that required reversal exposure to light. The E4 process had chemical reversal, as does E6. The reversal bath does this just prior to the color developer step. It is not critical at all. It does it every time. Only the first developer, first wash and first minute of the reversal bath step are done in the dark (if you use dip and dunk sink-line style processing), all the rest of the steps can be done in full room light. So about 10 minutes in the dark and you can switch the lights on. Of course if you process in a daylight tank, all the steps are done in room light after you load the film in the tank. I have been processing E6 since Kodak introduced it. It is easy, economical and quite within the reach of the average home darkroom enthusiast. Don't be discouraged. Only the first developer requires precise temperature control, and it is only for 6-6.5 minutes. The rest of the chemicals can drift a bit and you can still get spectacular results. The E-6 Kodak chemistry is all liquid concentrates, it mixes easily with no effort into working solutions and works with most, if not all municipal water, no special distilled water needed.
 

Photo Engineer

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Since the introduction of E4 and E6, either flashing or chemical reversal could be used at the users discretion. In E4, the chemical used was t-butyl amine borane, which was quite nasty. In E6 the chemical used is Stannous Chloride which is much milder, but subject to deterioration in solution.

Today, plastic reels are made with one transparent side so that you can flash with light evenly. Many are made with two transparent reels. Old reels were black and caused more problems with E6.

Kodachrome uses a mixture of flashing and chemical reversal. They use a Red and Blue flash and then a chemical reversal for the final development (Magenta).

All reversal processes suffer from variability due to the high pH of the color developer(s) used which usually run about pH 11 or higher. This high pH value is not stable and as the pH drifts down, the developer deteriorates. This is NOT true of the RA and C41 processes which use a much lower pH developer which is buffered optimally.

PE
 
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Photo Engineer

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If you use re-exposure by light, the opaque black reels would allow insufficient light to penetrate to the center of the film. At that time (E1, E2 and E3), Kodak suggested removing the wet film from the black reel and reexposing to light. This was to be done underwater to facilitate removal and rethreading of the film. (Can you imagine that? It was a chore I avoided.)

Anyhow, the reel designers changed to either all transparent reels or at least reels with one transparent and one black side.

PE
 

Discpad

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Kodachrome re-exposures

David, Kodachrome requires two (red and blue light) reexposures; one through the emulsion and the other through the base, not three re-exposures.

 

David A. Goldfarb

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Discpad said:
David, Kodachrome requires two (red and blue light) reexposures; one through the emulsion and the other through the base, not three re-exposures.
Click to expand...

Thanks, that makes more sense. I was puzzling for a moment at how they might do three.
 

markbb

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Ah, so at some point E6 didn't use a chemical for the reversal step, but it was done by exposing the film. Sounds like a nightmare!
 

Photo Engineer

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You misunderstood or my explanation was not clear.

E4 and E6 used chemical or light reversal. The chemical reversal was invented due to problems with light reversal in E1, E2 and E3. The problem was partially solved by 2nd party transparent and half transparent reels sometime in the 70s or thereabouts. Maybe even earlier.

PE
 
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