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bleach bypass for color desaturation


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#1 josé gerel

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Posted 15 January 2007 - 10:52 AM

Hello,

I am charmed of my inscription on this site, I wish you has all and all a very beautiful year full with satisfaction and beautiful films.

A first question, I wanted to know if it is more malignant to do one without partial bleaching on the negative one or on the positive one in 35mm.

Thank you.

Jose.
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#2 David Mullen ASC

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Posted 15 January 2007 - 11:09 AM

A first question, I wanted to know if it is more malignant to do one without partial bleaching on the negative one or on the positive one in 35mm.


I think you'll need to rephrase that question for us to understand it.
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#3 josé gerel

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Posted 15 January 2007 - 11:18 AM

Thank you for the answer David and sorry for my English sometimes.

Best regards.

José.
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#4 David Mullen ASC

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Posted 15 January 2007 - 11:24 AM

I'm not chiding you, I just want to know what your question is. Are you asking whether the desaturation effect is stronger when the bleach-bypass is done to the negative or the positive?

Or are you asking if there is some sort of long-term deterioration that is going to happen physically to the film if you use a bleach-bypass process?

I just don't know why you used the term "malignant".
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#5 josé gerel

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Posted 15 January 2007 - 12:26 PM

David, ?malignant? is a typically French term.

My outward journey question in the direction or I wanted to know if they were not dangerous to do one without bleaching on the negative one or on the positive one.

Best wishes.

Jose.
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#6 Dominic Case

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Posted 15 January 2007 - 05:10 PM

Malignant, dangerous, whatever. Still not sure, but this may help.

Bleach bypassing the negative has a greater effect on the image than bleach bypassing the print.

Partial bleach bypassing the negative is unreliable, the results may vary from one run to the next.

Partial bleach bypassing the print is not usually done, but the similar process (ENR or ACE) which is also a silver retention process can be provided to varying degrees.

Bleach bypassing is not known to have any long term effects on the negative or the print. As far as we know, the colour dyes do not fade any faster if there is still silver in the image.

If that answers your question, that is good.

If not, perhaps you might ask again, en Francais, and hopefully there will be someone on the list whose language skills are better than mine who could translate into English.
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#7 David Mullen ASC

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Posted 15 January 2007 - 05:10 PM

Dominic Case or John Ptylak of Kodak could probably say more about any long-term storage effects on bleach-bypassed material. The main problem is when you do it to the print because the extra silver causes more heat (infrared radiation) build-up/retention on the print, so it might not last as long in constant projection in a long theatrical release.
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#8 K Borowski

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Posted 16 January 2007 - 06:01 PM

Well, from what I know of B&W (which is made up entirely of grains of silver), your negative should be run through fixer to eliminate any silver halides (undeveloped silver, which will blacken slowly as it is exposed to light), it might need to be done longer with bleach-bypass to ensure that it has optimal permanence. Wait, strike that, thinking about it, there's probablyonly about half as much silver to be removed by the fixer in bleach-bypassed material, so no there's no difference in fix times, rather the FINAL WASH needs to be longer.

I'm pretty sure that this is done anyway (Dominic or John?) but there are tests you can do to determine if there are any silver halides left, which would be the only particles that'd cause problems because they change the look of the negative as they turn into black metalic silver themselves.

Well, your film should be OK if you store it correctly, no more, no less than regular color. Just remember that the B&W component is susceptible to certain compounds as well. Perfect example: color bleach, if accidentally splattered on B&W (don't ask me how I know this :-( ) will "bleach" away the silver from the image, so the compounds in the bleach, forget what they are at the moment, maybe potassium dichromate, and a strong acid, will eat the silver out of your print. I know that smog and ozone also have a bad effect on silver. Silver, on the other hand, isn't affected by light like color dyes are.

As long as your film is washed thoroughly enough (I'd check with the lab as they would probably need to wash the negative more if it were bleach bypassed than with color to eliminate fixer which is detrimental to silver not as much so with color dyes), it should be fine.

For added protection, it is possible to TONE the silver in the negative to deposit something in addition or as a replacement to the silver, but I don't know if this is practical to do with bleach-bypassed color. I'd recommend selenium or gold toner as the most stable.
Might even make for an interesting look. It'd be mighty hard finding a lab to do it; would probably cost a lot of money as that would be a custom job.

Hope that helps some

~Karl Borowski
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#9 Dominic Case

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Posted 17 January 2007 - 02:37 AM

Well, from what I know of B&W (which is made up entirely of grains of silver), your negative should be run through fixer to eliminate any silver halides (undeveloped silver, which will blacken slowly as it is exposed to light), it might need to be done longer with bleach-bypass to ensure that it has optimal permanence.

If you run colour stock through its normal process but with the bleach stage skipped, then you will get enough fixing and washing to remove the silver halides.

The wash time isn't really determined by how much chemicals have to be removed: it's to do with how swollen the emulsion is (which is pH and temperature dependent among other factors), and how quickly the chemicals permeate through the various emulsion layers out into the water. That is assuming that the wash water flow rate is enough to avoid a build-up of chemicals in the wash water itself.

For added protection, it is possible to TONE the silver in the negative

Hmmm,as far as I know a properly washed silver image is more permanent than any other type of image. The toning chemicals can have deliterious effects on the emulsion or even the base of the film over a long period of time. Many of the tinted and toned prints from the silent era have faded and shrunk more seriously than untreated black and white prints.

Perfect example: color bleach, if accidentally splattered on B&W

Karl mentions a good point which has tripped up a couple of people :o (no, not me :rolleyes: ) - never, ever, run your black and white film through a colour process. You will finish up with what might be called a white and white image. That is, clear film. Think about it. Explanation later for those who can't figure it out. Just - don't try it.
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#10 Phil Rhodes

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Posted 17 January 2007 - 07:30 AM

Hi,

Aren't there now at least stills films which are designed to evolve black dye image (rather than just the silver) so they can be put through a colour process?

Phil
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#11 David Mullen ASC

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Posted 17 January 2007 - 10:21 AM

"Chomogenic" b&w stocks. Don't know who still makes them, maybe Agfa or Ilford.
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#12 K Borowski

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Posted 17 January 2007 - 10:50 AM

Hi,

Aren't there now at least stills films which are designed to evolve black dye image (rather than just the silver) so they can be put through a colour process?

Phil


Kodak and Fuji both make one. Kodak's has changed names about five times in as many years. IDK what they're calling it this week, I think Portra B&WCN 400. There used to be two, an amateur and a professional version that were consolidated into the one B&W stock. I believe Ilford's is XP-2, though I might be mistaken on the number.

Theoretically, you could use either of these films in ECN-2, as there is no color shift to worry about. IDK if you'd get proper density or not, but with experimentation, it'd work

In stills, for optimal permanence, I believe Kodak is STILL recommending protective toning of B&W film and prints. I'm really not sure how toning would affect the support material, so Dominic's point is very valid that it might affect the size of the film which would make it difficult or impossible to print optically.

The ideal toning is with gold, which is highly resistant to oxidation. Over time, every element, except gold and platinum, will form compounds with oxygen. If you see old prints or negatives and hold them at an angle while shining light on them, you'll see this as a "shininess" on the surface of the film.

The reason I say that it might require longer washes is that residual fixer causes premature fading with B&W silver prints or negatives, whereas I don't believe color dyes are really all that effected by leftover fixer in the emulsion, although if you were to skip a wash altogether, I'm sure that'd caused premature fading of color.

Regards,

~Karl
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#13 Charles MacDonald

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Posted 17 January 2007 - 09:39 PM

Karl mentions a good point which has tripped up a couple of people :o (no, not me :rolleyes: ) - never, ever, run your black and white film through a colour process. You will finish up with what might be called a white and white image. That is, clear film. Think about it. Explanation later for those who can't figure it out. Just - don't try it.

(totally off topic but... Dominic you just brought back one of my worst moments on my first job. I was working at a camera counter in the early 70's - Young lad had left a rool of tri-x 36 exp to be processed. Unfortunatly he had bulk loaded it, even more unfortunatly he had found that he could buy empty Anscocrome cassettes real cheep. (ansco had a deal wher ethey would sell a special loader with enough film for 5 rolls.) to compound the problem he stuck a small red DYMO label that said TRIX on the red Anscochrome cassette.

You could see a very faint stain of an image on his film, the lab natuarly had not noticed taht it was tri-x and he had not been clear about it when he brought his film in so no-one had written "Black and White" as special instructions. At least the lab wrote off the processing charge, and they did follow the "please return cassette" instruction so he had his cassette back. I told him to PAINT it black!

(for those too young to rember, Anscochrome was a colour reversal film made by General Anailine and film corp,based on the Agfa colour patents. Usage was simalar to ektachrome but the process was unique to Ansco)
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#14 Dominic Case

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Posted 17 January 2007 - 10:46 PM

Anscochrome was a colour reversal film made by General Anailine and film corp,based on the Agfa colour patents.

Ah . . . Ansco!

Around that time, Ansco made the fastest colour film stock you could get. I bought a number of rolls of 35mm Anscochrome (I think it was 400 ASA but might have been just 200, memory fails me) to try to get some decent photos of the Aurora Borealis on a trip to Iceland. It came with process paid mailers, like Kodachrome.

Got a few good shots of the aurora, but with quite long exposures. A faster lens would have helped, but it was beyond my budget. Also some seriously fabulous sunsets.

There was a distinct magenta bias (noticeable on all the normal day exterior shots), which seems to have been characteristic of the stock.
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#15 Nick Mulder

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Posted 18 January 2007 - 12:36 AM

maybe potassium dichromate, and a strong acid, will eat the silver out of your print.

...silver that has been developed, its leaves undeveloped silver relatively unscathed ... I'm not sure of its affects on developed and fixed silver though. (I'm no expert though and maybe my definition of 'silver' is incorrect etc...)
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#16 David Mullen ASC

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Posted 18 January 2007 - 12:40 AM

Undeveloped silver isn't silver, it's silver halide. When exposed to light, it becomes potentially "developable" into silver; if unexposed, the developer leaves it as silver halide, which is then removed in the fixer and wash steps, leaving only silver.

In color film, the bleach step converts developed silver back into silver halide so that the fixer and wash steps can remove all the silver halide, leaving only color dye.
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#17 Leo Anthony Vale

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Posted 18 January 2007 - 04:20 PM

Ah . . . Ansco!

Around that time, Ansco made the fastest colour film stock you could get. I bought a number of rolls of 35mm Anscochrome (I think it was 400 ASA but might have been just 200, memory fails me) to try to get some decent photos of the Aurora Borealis on a trip to Iceland. It came with process paid mailers, like Kodachrome.

There was a distinct magenta bias (noticeable on all the normal day exterior shots), which seems to have been characteristic of the stock.


It was 500 ASA. The 16mm version was availiable only on an estar base, basically intended for high speed industrial and military use, rather than general production.

I shot some respooled anscochrome print film at 25 ASA. That had a magenta bias and was grainy for a print film, possibly it was out dated. I had to use prepaid mailers for that.

Come to think of it 8mm Ansco Moviechrome also had a magenta bias.

As for fast slide films, 3M/Ferrania had E-6 1000D and 640T. 1000D was decent and took a 1 stop push well.
The 640T had a weak cyan D-max. Always needed a bright high light in any shadowt shot.
Agfa had a 1000D E-6 at the same time, but don't recall using that.

Edited by Leo Anthony Vale, 18 January 2007 - 04:21 PM.

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#18 Dominic Case

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Posted 18 January 2007 - 05:18 PM

...silver that has been developed, its leaves undeveloped silver relatively unscathed

Film emulsions start off with the silver in the form of silver halide crystals (the halide is usually bromide, but can include a little chloride too).

Development converts the exposed crystals to silver. It doesn't touch the unexposed crystals, which remain as silver halide.

Fixing dissolves the unexposed (and therefore undeveloped) silver halide into solution. That's the silver that you can recover from used fixer solution.

Bleach converts silver back to an ionic form, sometimes silver halide, sometimes other complex compounds. Whatever they are, they are then capable of being dissolved away by fixer.

If you bleach before fixing (as in a regular colour process), the exposed silver image is therefore reduced and removed - leaving just the colour dyes in the case of colour emulsions.

Household bleach is not necessarily the same type of chemical as photographic bleach: it has a different job to do.
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#19 Christophe Collette

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Posted 23 January 2007 - 11:28 PM

Hey Jose, I don't know if you'll stick with us on this forum, but I could help you with your english... It is not a problem for me, I told you already, if I am on the forum at the same time as you, I am logged in quite often, just send me a message, I'll help you out translating either your questions or your answers!

José, comme je te l'ai déjà dit, il me ferait plaisir de traduire tes questions si tu veux... Ou encore de traduire les réponses, demande-moi, si j'ai le temps, ça me fera plaisir!


Christophe
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