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  1. #21
    wogster's Avatar
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    Quote Originally Posted by StoneNYC View Post
    What's RA4? :/

    Also, I really don't understand color chemical much, I know what fixer is from B&W but what exactly is bleach? Like is it the same as Clorox bleach? Or something entirely different?

    I'm totally ignorant about color and only half way ignorant about B&W


    ~Stone

    The Noteworthy Ones - Mamiya: 7 II, RZ67 Pro II / Canon: 1V, AE-1 / Kodak: No 1 Pocket Autographic, No 1A Pocket Autographic

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    Photographic bleach is chemically quite different from household bleach.

    Colour developers do two things that are important, they turn exposed silver into elemental silver, and as a side effect they form dyes in the emulsion. These dyes are the reverse of the image colour, in other words blue exposure is a yellow dye, green exposure is a magenta dye, and red exposure is a cyan dye. In a process like C41 or RA4, the bleach turns the elemental silver, back into silver halide, and the fixer then removes all of the silver, but leaves the dye image alone. In RA4 you essentially end up with a negative of a negative which since the colours are reversed, they end up the way the original image was.

    E6 works a little differently, in that there are two additional steps. The first developer works similar to a B&W developer, it develops the silver, a chemical reversal step then chemically "exposes" the formerly unexposed silver, which is undeveloped at this point. The next bath is a colour developer which develops the chemically exposed silver and forms the dyes, but leaves the formerly developed silver alone. If you take the film out of the chemistry at this point, it would be black because all of the silver has been exposed and developed. The bleach then turns all of the exposed silver from both steps back into silver halide, so that the fixer can remove it.

    In all cases, a stabilizer step is used to set the dyes in the emulsion, this often includes a chemical that makes water slide off the film, similar to what photo-flo does for B&W.
    Paul Schmidt
    See my Blog at http://clickandspin.blogspot.com

    The greatest advance in photography in the last 100 years is not digital, it's odourless stop bath....

  2. #22
    StoneNYC's Avatar
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    agitation frequency of Blix in E-6 tank processing

    Quote Originally Posted by wogster View Post
    Photographic bleach is chemically quite different from household bleach.

    Colour developers do two things that are important, they turn exposed silver into elemental silver, and as a side effect they form dyes in the emulsion. These dyes are the reverse of the image colour, in other words blue exposure is a yellow dye, green exposure is a magenta dye, and red exposure is a cyan dye. In a process like C41 or RA4, the bleach turns the elemental silver, back into silver halide, and the fixer then removes all of the silver, but leaves the dye image alone. In RA4 you essentially end up with a negative of a negative which since the colours are reversed, they end up the way the original image was.

    E6 works a little differently, in that there are two additional steps. The first developer works similar to a B&W developer, it develops the silver, a chemical reversal step then chemically "exposes" the formerly unexposed silver, which is undeveloped at this point. The next bath is a colour developer which develops the chemically exposed silver and forms the dyes, but leaves the formerly developed silver alone. If you take the film out of the chemistry at this point, it would be black because all of the silver has been exposed and developed. The bleach then turns all of the exposed silver from both steps back into silver halide, so that the fixer can remove it.

    In all cases, a stabilizer step is used to set the dyes in the emulsion, this often includes a chemical that makes water slide off the film, similar to what photo-flo does for B&W.
    That was a very simplified and easy to understand explanation, thanks.

    As far as how the chemical "tells the difference" between the chemical development and the actual exposure, even though to the eye it would appear black, the actual mechanics at a microscopic level would be different? Which is why the bleach can tell the difference between the chemically induced blackness and the actual exposure? Wow I'm learning so much! It was suggested to me privately that I actually read a book haha, I think it might be time for that so I don't take over all of the threads with questions like a kid does "why this Dad? But then why...? And how Dad?" Haha

    So, you don't need photo flow / wetting agent when using E-6/C-41?


    ~Stone

    The Noteworthy Ones - Mamiya: 7 II, RZ67 Pro II / Canon: 1V, AE-1 / Kodak: No 1 Pocket Autographic, No 1A Pocket Autographic

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    ~Stone | "...of course, that's just my opinion. I could be wrong." ~Dennis Miller

  3. #23
    RPC
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    Perhaps you didn't mean to write it this way, but for correctness I submit the following:

    Quote Originally Posted by wogster View Post
    ...they turn exposed silver into elemental silver...

    ...and the fixer then removes all of the silver...

    ...chemically "exposes" the formerly unexposed silver...

    ...because all of the silver has been exposed and developed.

    Except in the term "elemental silver", the word "silver" should be replace by "silver halide" in all of the above


    Quote Originally Posted by wogster View Post
    The bleach then turns all of the exposed silver from both steps back into silver halide, so that the fixer can remove it.

    In the above the word "exposed" should be replaced by "developed".

  4. #24
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    Quote Originally Posted by StoneNYC View Post
    That was a very simplified and easy to understand explanation, thanks.

    As far as how the chemical "tells the difference" between the chemical development and the actual exposure, even though to the eye it would appear black, the actual mechanics at a microscopic level would be different? Which is why the bleach can tell the difference between the chemically induced blackness and the actual exposure? Wow I'm learning so much! It was suggested to me privately that I actually read a book haha, I think it might be time for that so I don't take over all of the threads with questions like a kid does "why this Dad? But then why...? And how Dad?" Haha

    So, you don't need photo flow / wetting agent when using E-6/C-41?


    ~Stone

    The Noteworthy Ones - Mamiya: 7 II, RZ67 Pro II / Canon: 1V, AE-1 / Kodak: No 1 Pocket Autographic, No 1A Pocket Autographic

    Sent from my iPhone using Tapatalk
    When the colour development takes place, the reaction between the colour developer and the exposed silver and other chemicals in the emulsion cause the coloured dyes to form, which forms the actual image. The silver is no longer required, and the bleach converts the silver back to a silver salt, the fixer then removes all of the silver salts, leaving no silver in the actual image.
    Paul Schmidt
    See my Blog at http://clickandspin.blogspot.com

    The greatest advance in photography in the last 100 years is not digital, it's odourless stop bath....

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