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Filed under: Lighting •Production •Tips •Training •

Mysteries of Color and Light

Additive color means that mixing the three primary colors together will “add” up to white light. The additive primary colors are red, blue and green. You can create any color your eye can see by mixing these three colors together, as long as you are looking at the light and not at something it is illuminating. Adding color makes the light source brighter.

Subtractive color means that mixing the three primary colors together will “subtract” to black. This is how printing works, and it is also how we see color: colors not present in an object lit by white light are absorbed, or subtracted, leaving the object’s color to be reflected. The subtractive primaries are cyan, magenta and yellow. Adding color makes the result darker.

Film is a subtractive process, because the dyes on the print are filtering, or removing, color from the white light of the projector. Red light is created by dyes on the film filtering out all the light that’s not red, etc. Black is created by completely blocking the light. So while labs may give printer lights in R-G-B numbers, they are really telling you C-M-Y printer lights as they are printing onto a subtractive medium from a negative image.

Gels and filters are also subtractive. An 85 filter, for example, holds back (or subtracts) some of the blue in daylight in order to create a “proper” image on 3200k film. Adding Lee 122 “Fern Green” to a tungsten light subtracts everything in its spectrum except for a yellow-greenish color. Gels and filters never add color, they only remove it.

Printed materials, such as magazines, use a further dye that is just plain black, as cyan, magenta and yellow inks blended together don’t make as rich a printed black as actual black ink. So instead of simply CMY, printers use CMYK—where “K” is black ink. In a way this is similar to the bleach bypass process: silver halide crystals are bound to the colored dyes in the film, and these crystals react when struck by light. During processing the silver is normally removed using a bleach process, leaving behind colored dyes that were activated by the light-struck silver. Bleach bypasses skips all or part of the bleaching process, leaving behind varying degrees of silver.

When applied to print stocks the effect is to increase contrast by dramatically enriching the shadows, as well as desaturating colors. You could say that the silver is the film equivalent of “K” in the ink printing process: since dyes can only block so much light, and the silver physically blocks all the light, the remaining silver causes much deeper blacks.

Using the same process on a negative causes the opposite effect: highlights blow out, because light is prevented from passing through the negative and hitting the positive print stock.

That’s it for now. I’m constantly amazed at how much there is know about cinematography. It sure does keep life interesting.

Art Adams is a working director of photography based in the San Francisco Bay Area. His web site is at www.artadams.net.

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Great article! My brain melted, but I liked it.

Posted by ninjanels  on  03/26  at  11:06 AM

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Sorry about that. Is it the concepts or my writing that turned up the heat? If it’s the writing then I can work on that.

I’ve discovered that I like to feel my brain hurt. It’s fun learning about the hidden side of why things work.

Posted by Art Adams  on  03/27  at  12:12 PM

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This confirms some things I had suspected. One is that building your own lights using consumer florescent bulbs may result in gaps in the spectrum you’re using.

I’ve thought about using an inexpensive spectroscope to get an idea about the “spectrum density” (I made up that term but it sounds good) of various photographic light sources. I’ve found these two that might work:

http://scientificsonline.com/product.asp_Q_pn_E_3120400 $1.95

http://scientificsonline.com/product.asp_Q_pn_E_3053066 $5.95

Have you tried this? What do you think?

Peace,

Rob:-]

Posted by Rob  on  03/30  at  09:16 AM

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A quick question: if silver retention is done to the negative, what effect would it have on the shadow areas? Besides graininess, would the contrast in the shadow area be increased as well?

Likewise, a similar question: if done on the positive, what effect would it have on the highlight areas?

Cheers,
Derrick

Posted by .(JavaScript must be enabled to view this email address)  on  04/19  at  08:51 PM

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I think the section of this article relating to additive and subtractive primary colours helps to answer something I was wondering about a while ago: Why exactly does striking a positive print from a colour negative create a positive image?

I think that the answer lies in understanding which of these sets of primary colours balance each other out (R/C, G/M, B/Y?).

Unfortunately, right now my brain is frazzled so I’ll have to work it out later.

Posted by .(JavaScript must be enabled to view this email address)  on  06/05  at  10:27 AM

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Okay, I’ve figured it out. It’s very simple if I’m right, probably one of the first things you’d learn if you studied photography formally, but I’m self-taught.

What confused me is hearing and reading references by cinematographers to red, blue and green layers on negative film. I assumed they were referring to the colours of the dyes, which I suppose must be cyan, magenta and yellow on a negative - hence the colour of the image you see when you hold developed negative up to the light. It’s nice to put things together.

Excuse me for cluttering up your comments section.

Posted by .(JavaScript must be enabled to view this email address)  on  06/05  at  10:53 AM

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