Colour Spaces - Linear, Log, sRGB, eh?
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Colour Space
Fix this page by referencing this page http://prolost.blogspot.com/2005/05/log-is-new-lin.html
All digital colour is a representation of real colour
real colour is an amount of energy at a particular wavelength
We can see the wavelengths between ultra violet and infrared known as the visibible range
Our eyes cant actually see colours apart from red green and blue, due to the way the rods and cones in our eyes work
Digital colour takes advantage of this and represents all colours as a fraction of red green and blue.
For simplicity just think of the range between zero and one where one is the highest value available
The amount of red green and blue that a monitor or projector is determined by the values
The amount of energy that is displayed for a given value is determined by the Look Up Table (LUT) that the display is using.
sRGB : Screen
Most of the time when working for final output via a computer screen, we work in sRGB colour space. This is pretty much what you see if what you get. A mid grey pixel will have a value of around 0.5
Linear : Light
If you take an sRGB monitor and apply a LUT of about Gamma 2.2, you get a very dark looking image without the LUT applied. But when the lut is applied you are working in Linear Space
When working with lighting, its easiest to think about things with a linear relationship between values. If I double the amount of energy in a light (disregarding inverse square falloff) the resulting image will be twice as bright. When producing computer generated images. If textures are produced in linear space
Log : Film
Log files aka cineons are designed to be printed onto film and projected.
They use a logarithmic relationship between the values and the amount of energy
This has the adavantage that the information in the black end of the spectrum is more detailed
if you think about an 8 bit image with integer values from 0 to 255
the difference between 1 and 2 is double, but the difference between 254 and 255 is only a small amount
using a log scale, the information can be concentrated where the detail is needed in the back end of the spectrum
Conversions
sRGB to Linear is a Gamma of 0.4545
Linear to sRGB is a Gamma of 2.2
Linear to Log is just that
Log to Linear is just that
Example images
- This page was last modified 12:36, 28 September 2007.
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