Saturation and Contrast

[Seung Han]

Hello,

Can somebody explain the relationship between saturation and contrast? I understand them separately but have difficulty wrapping my brain around using them together in describing an image.

For example, can an image be destaurated with high contrast? Or vice versa?

This just popped into my head and suddenly turned it into a pretzel. I don't know why...

 

[Matthew Bennett]

David Mullen will chime in I'm sure with a wikipedia-quality response.

yeah, you can have high-contrast and desaturation, though.

 

[Hans von Sonntag]

If you increase contrast you automatically increase saturation. This happens because you "compress" the values of the pixels (vague discription) hence the higher saturation. The same happens in the opposit direction if you reduce contrast. This is the reason why RedLog looks desaturated and RedSpace "right". In RedSpace values are compressed at the "right" spot and therefore contrast and satuartion are enhanced. Visually such a "compression" can be described with curves.

As always with pixels there are algorithms that discribe this phenomenon. There are some on the board who are quite familiar with maths, surely not me.

Hans

 

[Rudi Herbert]

The Bleached look of Private Ryan and the countless myriad of its followers is both desaturated and very contrasty...

 

[Graeme Nattress]

Saturation is basically how "pure" a colour is. If you think in terms of paint, adding white paint to a colour makes it less pure, and more pastel. That's less saturated.

Contrast is not a thing which applied to a colour, but to a whole image. A contrasty image is one where there exists both dark and bright areas. The more dark and bright you see in an image, the less mid-tones there are, the more contrasty it is.

Depending on how you alter contrast, it can make colours appear more or less saturated. If you apply contrast to an image in RGB, then colours tend to look more saturated. If you apply contrast to the "luma" of the image while it's in a luma/chroma colour space rather than RGB, you won't get quite the same effect.

Graeme

 

[Seung Han]

thanks guys. Your responses have cleared up the fog in my head. Your technical responses now lead me to a new line of inquiry.

How do you think/feel a filmmaker should decide on the saturation and contrast for a project? I know it depends on the story and the vision but is there a general guideline in deciding the look of the piece in terms of saturation and contrast?

Like if I have low saturation but up the contrast in the "luma" as Graeme points out, is this a particular look for certain types of films these days?

I guess I'm curious about how cinematographers and post people feel are the emotional and dramatic qualities of saturation and contrast.

Again, thanks for the responses, they are very helpful.

 

[Charles Angus]

I don't think general principles can be applied to this; cinematography is an art, and as such, the reasoning behind it defies generalization.

I would say if you want to learn about this, just watch some movies and think about how the contrast and saturation is working with/against the story and why you think it was effective or not.

 

[Dan Hudgins]

Dye and Silver

Dye and Silver

Like if I have low saturation but up the contrast in the "luma" as Graeme points out, is this a particular look for certain types of films these days?

When color negative movie film is processed the dyes form at the same time as the silver image, the dyes are made of a byproduct of the developing agent when it forms silver, so the dye image is lower resolution.

If you do not take out the silver with silver bleach you get more contrast and the silver locks some of the light so the dark areas have less color. If you compensate for the double plus density you get less color saturation for the same contrast (you can compensate for the contrast gain in bleach bypass in the DI CC).

You can also change the color saturation and contrast in film with pull and push processing. If you pull process and bleach bypass you get less color for the same contrast and more blown out whites. Since the silver tends to come out a little brown in the negative, it looks a little blueish green in the print, hence the trend to make things look bluish and greenish.

Also in bad labs that try to save water, you get a pink stain in the negative, which comes out as a green cast in the print.

People now use LUT to adjust the color to get the bad lab look on video.

If you mix two gradings of your footage one color and one black and white with different gammas and curves you can adjust the contrast and saturation in different tones of the image, something like what happens in bleach bypass film where the thin areas get more dye filtered light and the heavy areas are dominated by the silver blocking all the light.

 

[pietro jona]

You can have a high contrast BW picture. That one has no saturation at all..

 

[JustinGD]

I don't think general principles can be applied to this; cinematography is an art, and as such, the reasoning behind it defies generalization.

I would say if you want to learn about this, just watch some movies and think about how the contrast and saturation is working with/against the story and why you think it was effective or not.

I agree with this, but I'm also interested in how the members on this board perceive the use of contrast and saturation.

Every rule has an acceptation, but general rules like a low camera angle gives a character power or the 180 degree rule are generalizations, but still good to know.

 

[Graeme Nattress]

Contrast and saturation can be altered independently of each other. However, as mentioned above, making an RGB image darker will have the effect of increasing the saturation.

 

[Blair S. Paulsen]

Flavor

Flavor

Quick example:
To try and make an image that was underexposed look "right" you have to "push" it in DI, that gamma shift often desaturates the color which can be restored by upping the saturation control.

The careful control of contrast and saturation can have a substantial impact on the feel of a piece, I like to think of it as the visual equivalent of saying the same words with different intonation.

Bottom line, a talented colorist can add a great deal to a piece.

 

[Dominic Jones]

The careful control of contrast and saturation can have a substantial impact on the feel of a piece, I like to think of it as the visual equivalent of saying the same words with different intonation.

That's a great analogy Blair... Mind if I nick it from time to time??

Bottom line, a talented colorist can add a great deal to a piece.

Wiser words were never spoken my friend!...

 

[Seung Han]

Again, thanks to everybody for clearing up the technical aspects of these qualities to the image. Always best to understand the foundation before trying to use it as tools.

So I am also interested like JustinGD in what the cinematographers and colorists here think of these elements of the picture. I always hear so much about how the other aspects of the image impact the viewer but much less so for saturation and contrast. I am not so much interested in the style element of it but moreso if storytellers believe there is a dramatic/emotional guideline for these elements of the image.

I was watching "Children of Men" and it seemed desaturated with high contrast (is this right? if not can someone correct me?), and I was thinking about how it made the environment feel very bleak and hopeless but the emotions of the characters raw. As oppose to the rich colors in "In the Mood for Love" which made me feel the passion of the characters almost in opposition to their framing in the hallways and doors which made the characters feel like they were trapped by their desires. Then it made me wonder if filmmakers decide these elements form some sort of basic guideline once they figure out the mood of their stories. Or if it was just a gut instinct they followed where one couldn't be wrong...

 

[Daniel S Williams]

Children of men was very contrasty and desaturated, much like Private Ryan. Seems to be the trend nowadays.

Lens MTF can also have a direct effect on contrast.