Posts Tagged Color Science
FLUT Color Science from Red One explained
A Look Up Table, is a table of values that represent a mathematical formula that has already been calculated for every value you could want. So instead of doing the calculation you look up the answer you want by tracing along a table. We use look up tables in programming when we it’s easier just to hand over the values than to try to describe the formula and/or when we need speed and have plenty of memory and memory access is faster than the actual calculation. (In some cases the table is combined with calculation)
From the point of view of a user a Look Up Table, just means a transformation, in our case the transformation of one color value to another.
A floating point number is a way of writing a number where the decimal point can move. (In computers its the binary point.) This is incontrast to a “fixed point” number where there is a certain fixed number of digits on either side of the point. Floating points are useful because they allows you to represent really large numbers by moving the point all the way to the end or tiny numbers (between 1 and zero) by moving the decimal point all the way to the front and to use either type of number together in whatever math you are doing.
From the point of view of the user floating points mean, more precision, so the color transformations are less likely to cause posterization for example.
Since floating point numbers are already in use internally in most post production software this could also help make Red’s color science more portable.
by
IBloom
http://www.crimsonworkflow.com/home.htm
Red Raw: Part 1
The Red Color Workflow:
The Red camera represents a new approach to motion image capture that relies on post processing, rather than in-camera processing, to deliver images that are appropriate for use in both video and film finishing formats. The files that are written directly by the camera
represent – in compressed form – the actual data captured by the Mysterium sensor, without any manipulation for specific display systems. Because of this, when working with Red images it is necessary to understand some of the basic principles of working with digital images in order to determine the proper path for an intended delivery format.
Without going into unnecessary details, the Mysterium sensor in the Red cameras is a single sensor that captures color images by means of a color filter array that is superimposed on the individual pixel sites on the sensor. The particular pattern that is used is called a Bayer pattern, and consists of alternating rows, each of which has a combination of either red and green pixels (i.e., GRGR etc.), or blue and green pixels (i.e., BGBG etc.). In order to create a “normal” RGB image, a process called a Debayer (also referred to as “demosaic”) is invoked, which uses some rather complex math to predict what each of the individual pixel sites would contain in all three color components by combining the values of the surrounding pixels for each of the colors not directly represented by each individual pixel. A good debayering algorithm can be very accurate, and the algorithm used by Red is very good indeed. Since the red, green, and blue filters used on the sensor are not absolutely “pure,” and the tiny lenses that focus each filter’s light on the image element itself are not perfect, there is a certain amount of “crosstalk” that occurs between the values of each pixel – in other words, the red pixels also contain a certain amount of blue and green, the blue pixels contain a certain amount of red and green, and the green pixels contain a certain amount of red and blue. The debayering algorithm is specifically designed by Red to account for these variations, based on their specific sensor characteristics. The sensor also has a “native” white point, that is, a specific point in the color spectrum that is considered to be white. In order to achieve a more “pure” – and thus accurate to the actual scene – image on a specific type of display, a color matrix is then used that alters each component by adding or subtracting a bit of the other two components, based on the characteristics of the intended display, in particular, the display’s specific white point. In the world of Red, this color matrix is usually identified using the term Color Space.
Will see more about Color Space, Gamma etc in coming posts…
Excerpts from Assimilate White paper by Mike Most (Colorist/Technologist)