Swapping LUT Components

Swapping LUT Components

A very powerful capability of ColourSpace is the ability to replace individual LUT components, using the LUT Adjustment tools options.

An obvious application is to use the 1D (Grey Scale) LUT component from one calibration LUT and combine it with the gamut only (3D) calibration component from another LUT.

This can be of interest when using lower-end probes to perform full volumetric calibration, which introduce a high number of inaccurate probe readings due to poor low-light capabilities of the probe.

When profiling for LUT based calibration, the usual approach is to use one large volumetric profile to generate the final LUT.

However, there is nothing wrong with using one profile focused on just the Grey Scale, and another profile for the Volumetric Gamut, and then combine the grey scale from one LUT with the gamut component from the other.

Initial LUT Generation

First, focusing on the grey scale, a Matrix Calibration or a Quick Profile can be used to generate a calibration LUT focussing on the grey scale.

Then a cube based Characterisation can be used to generate a second, volumetric gamut focused, calibration LUT

The 1D LUT component can then be combined with the 3D LUT component to generate a new 3D LUT.

Combine Separate Grey Scale and Gamut 1D & 3D LUT Components

The first step is to extract the gamut only component from the volumetric LUT by nullifying the 1D (grey scale) component.

The second step is to extract just the 1D grey scale component from the second LUT.

The Grey Scale component can then be combined with the gamut only LUT.

The result is a new 3D LUT, with the grey scale (1D) component from one LUT, combined with the 3D, gamut, component of a second LUT.

The process is:

• Make the first volumetric gamut LUT using a cube based profile
• Save the LUT into the Manage Spaces library
• Export the LUT using a 1D RGB 3 channel LUT, such as the VCGT format
• Import the new 1D LUT back into the library

The new imported LUT will be expanded into a full 3D volumetric LUT, but with only 1D data contained within it.

• Open original volumetric gamut LUT within LUT Tools, and select LUT Adjustment/Maths/Subtract
• From the drop down list select the re-imported 1D LUT, and Apply

The resulting LUT will have the 1D grey scale component nullified from the full 3D LUT, not just deleting the grey scale points as that is not the correct process required. The entire 1D component must be removed from the full volumetric 3D LUT, as can be seen below.
(Click on one or other of the images to directly compare.)

• Make a second LUT using a Matrix Calibration workflow or Quick Profile
• Save the LUT into the Manage Spaces library
• Export the LUT using a 1D LUT, such as the VCGT format
• Import the new 1D LUT back into the library
• With the new gamut LUT, with original 1D component nullified, held within LUT Tools, select LUT Adjustment/Maths/Add
• From the drop down list select the imported 1D LUT, and Apply

The result is a new 3D LUT, with the grey scale (1D) component from the Matrix or Quick Profile generated LUT combined with the 3D, gamut, component of the volumetric LUT.