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Fuji 250d & Bleach By-pass

Published : 8th October 2004


Hi there!,

I would love to hear if any of you have shot 250d (day/exterior) and bleach-bypassed it? I'm trying to run some test to see if its just better to wait till the printing and doing it there or risking to go underexposed to achieve a tougher contrast and a heavy unsaturated look...have any of you found an interesting result or something you think I don't have to miss in the tests?

I was wondering, what happens if you skip-bleach the negative and then you skip-bleach the positive?

Well thanks all in advance.

Alberto Anaya



>I was wondering, what happens if you skip-bleach the negative and >then you skip-bleach the positive?

You get a LOT of contrast and desaturation -- and more graininess. I've done it, on a short film called "Stuck", but it was skip-bleached low-con Fuji F-400T and the skip-bleached print stock was Fuji 3519, which was slightly less contrasty to begin with (it's now called Fuji 3510.)

Skip-bleach processing the negative tends to blow-out your highlights more while skip-bleach processing the print tends to darken the shadows and "crush" the blacks.

David Mullen
Cinematographer / L.A.



>I was wondering, what happens if you skip-bleach the negative and >then you skip-bleach the positive?

Some recent, popular examples of bleach by-pass processing (either negative or print or both) are

Minority Report
Seven
Fight Club
Get Carter (remake)
Pitch Black
The Grifters
The Cell ("inner world" scenes only; these scenes are also some of the first examples of 35mm scanned to HD and shot to film via Arrilaser)

Daredevil is an example of Digital Intermediate being used to reproduce a bleach by-pass look.

Matt Davey
NYC - Digital Film Recordist



David Mullen ASC writes :

>You get a LOT of contrast and desaturation -- and more graininess.

I've done this look in post. It's a lot safer. Particularly as you can't get insurance if you're bleach bypassing the neg.
Someone correct me if I'm wrong

Mark Wiggins
DP/Operator/London
www.productionbase.co.uk/cv/scare



>Polycontrast paper has a special emulsion that responds with varying >contrast to varying colors of light.

Using this principle in motion picture negative would of course be counter-productive, as using a colour filter on an original scene would affect the contrast in a much more complex way. However, this wouldn't be a problem in print emulsions, when printing from a black and white negative.

In fact pan separation pos film (for making tri-seps) behaves in this way, producing slightly different gammas (or contrast) to different colours of exposure. (For normal tri-seps, this means that the different seps (R,G,B) require different developing times to get the required matching gammas.)

If you made a print on this stock from a b/w negative, you could in theory alter the contrast of each shot by putting colour corrections into the printer lights. However, in practice, this stock wouldn't be suitable for making b/w prints, as you wouldn't be able to get the gamma anywhere near high enough.

Dominic Case
Atlab Australia



So just out of interest, "Minority Report" did use bleach bypass then??

The look is very cold and warm is turned to white, how was this achieved? How does bleach bypass process work? What happens to the neg / grade in this process? What stock is best for bleach bypass?

Tom Coghlan
clapper/loader
London



There is no right or wrong color negative stock for doing a bleach-bypass -- it just depends on the look you want. Bleach-bypassing the negative increases density (dramatically) as if you overexposed by more than one stop. It also increases contrast and it increases graininess (because you are leaving silver grains in the image.) Most people compensate for the increase in density by rating the stock one stop faster -- but then you are
also increasing the graininess this way as well. So if you were going to try and mitigate some of the graininess, you would use a slower-speed film stock ("Pitch Black" and "The X-Men" used 5245 for their skip-bleach negative scenes.) However, "Minority Report" did it to Vision 800T for more graininess. And I don't think they underexposed the stock, rather letting the increase in density cause things to blow-out more.

You could use a low-con stock in combination with the skip-bleach neg processing, if you were more interested in the desaturation than the contrast increase. I did it once to a short film shot on low-con Fuji F-400T.

The way it works : is this light exposure causes silver halide grains in a film to become developable. During processing, an equal amount of color dye is generated for each amount of metallic silver that it formed (developing causes the exposed silver halide grains to be converted to metallic silver.) The bleach step converts metallic silver back into silver halide. The fixer and wash steps remove unexposed silver halide as well as the now reconverted silver halide, leaving only color dye grains. If you skip or bypass the bleach step, the metallic silver is never reconverted to silver halide and so it never removed during the fixer and wash steps, leaving silver in your image. When done to the negative, you gain density in the highlightsm which burn out faster. When done to the positive (print) you gain density in your blacks, causing shadows to go darker faster. Color is desaturated because of the addition of silver.

There is more graininess when you do the process to a negative instead of a print because camera negative stocks have larger silver halide grains in them, because they have to be more sensitive to light than lab intermediate and print stocks, which have a very low ASA.

David Mullen
Cinematographer / L.A.



David Mullen wrote :

>If you skip or bypass the bleach step, the metallic silver is never >reconverted to silver halide and so it never removed during the fixer and >wash steps, leaving silver in your image.

Would you further explain why this happens to the highlights as opposed to the blacks?

>When done to the positive (print) you gain density in your blacks, >causing shadows to go darker faster. Color is desaturated because of >the addition of silver.

If the reason why this happens is different (ie, not just the opposite) for the positive print than for the negative, would you also explain why it only affects the blacks?

>Color is desaturated because of the addition of silver.

Would you explain how the silver being left over desaturates the color?

>There is more graininess when you do the process to a negative >instead of a print because camera negative stocks have larger silver >halide grains in them, because they have to be more sensitive to light >than lab intermediate and print stocks, which have a very low ASA.

Would you please correct me if any part of the following statement is wrong... Faster films (ones with higher ASA ratings) gain their speed (light gathering capabilities) by having larger silver bromide crystals in them. Because only a portion of a crystal needs to be struck by a photon (a particle of light) for the whole crystal to be "developed," a larger crystal increases the chances of it being struck and hence registering some brightness in that portion of the film frame.

Cheers,

Piotr Jagninski
Gaffer / New York City



>Would you further explain why this happens to the highlights as >opposed to the blacks?

Because it's a negative. If you add density to a negative you block light from hitting the print stock, creating a bright spot.

>If the reason why this happens is different (ie, not just the opposite) for >the positive print than for the negative, would you also explain why it >only affects the blacks?

Because now you are adding density to a positive image, which means light can't get through those areas as well. As a result, they look dark.

>Would you explain how the silver being left over desaturates the color?

If you leave a layer of silver on top of the dyes in the film you're not going to get much color out of them, just as if you put a light layer of black paint over a colourful painting.

Art Adams, DP [film|hdtv|sdtv]
Mountain View, California - "Silicon Valley"
http://www.artadams.net/



In a negative, the brightest parts of the original scene are the most dense; therefore in a B&W negative there is more silver in the brightest areas. In a print, the darkest parts of the image are the most dense; therefore in a B&W print, the dark area have the most silver.

So the same principle work with bleach-bypass processing color film where the silver that forms during development is left in rather than removed by the bleach, fixer, and wash steps.

The color is desaturated because you have a layer of silver left on the film in equal proportion to color dye, and silver is monochromatic (black.)

David Mullen ASC
Cinematographer / L.A.



>Would you please correct me if any part of the following statement is >wrong...

No-one else mentioned this in responding to Piotr's list of questions. Perhaps because his statement was, in fact, correct; ... but just to confirm the point (which was about the relationship between graininess and speed)

When a photographic emulsion is developed, the silver bromide crystals are converted to silver grains, (and in colour, to dye). This happens thousands of times faster to "exposed" crystals. Each crystal contains millions of ions of silver and bromide: when photons hit the crystal, they knock electrons out of individual bromide ions, resulting in tiny spots of silver on the crystal. Never mind the other details: effectively, a crystal with a
spot of silver will get developed quickly, while one without (i.e. unexposed) will take many times longer (though eventually it, too, would get developed, which is what causes the increased fog level of push-processed film).

Since bigger crystals present a larger target to a stream of photons, an emulsion consisting of bigger crystals will reach a certain exposure with less light (fewer photons) than an emulsion containing more, but smaller, crystals.

Emulsions contain a range of sizes of crystal, to respond to a wide range of brightness (more latitude). Underexposed images (less light, fewer photons) rely more on the larger grains, which is why underexposed scenes look grainier (there are other reasons as well, but that's another story).

Dominic Case
Atlab Australia



>Underexposed images (less light, fewer photons) rely more on the >larger grains, which is why underexposed scenes look grainier (there >are other reasons as well, but that's another story).

Tell me another story! Please, continue. Unless it's in your book, in which case I'll just go back and look it up.

Art Adams, DP [film|hdtv|sdtv]
Mountain View, California - "Silicon Valley"



Art Adams wrote :

>Tell me another story! Please, continue. Unless it's in your book, in >which case I'll just go back and look it up.

I second that sentiment! I would just love to know the details down to the... hmmm... I dunno, can you get smaller than a photon and still see anything?

Cheers,

Piotr Jagninski
Gaffer / New York City