Interesting discussion. Here's a short overview of Light Space. I bought Light Space last year solely based on all the LUT support tools they offered. No other calibration software package I looked at had these LUT tools. From my experience at AT&T Bell Labs, any competent R&D organization needs lots of tools to support the any kind of new development and to answer/debug questions from the field. Seem to me these guys at Light Illusion had a lot of experience with LUTs and knew what they were doing … just based on all the LUT tools they offered.
The most important calibration technique I learned from using Light Space is how to keep the projector/display as linear as possible as part of pre-calibration workflow. Why is this important? It’s all about the 16.77 million accurate colors (for an 8bit color depth projectors/displays). The more linear the display, the easier it is to extrapolate all the colors accurately between the meter’s hard reads. The more linear, the faster the calibration. The more linear, the smaller the number of hard reads the meter must do to provide 16.77 million accurate colors. The more linear, the more expensive the projector/display. Every projector and display I’ve calibrated with LS is highly non-linear … except for my $12,000 Penta 37” DH2linePro broadcast grade 1 monitor.
Here’s an example of Epson’s 6020 projector’s linearity. My understanding of linearity is it's the amount of RGB color “cross distortion” across the brightness levels from black to white. To assess linearity, LS plots grayscale color luminance from Blk to Wht along with the associated RGB values. Ideally, a gray scale increase in luminance from Blk to Wht should have equal units of RGB (0,0,0; 16,16,16; … 235,235,235). In Diagram 1, the Epson projector is at its Before “default settings”. Its linearity has unequal amounts of RGB as noted in diagram 1. If the RGB amounts were equal, the RGB lines would ride nearly on top of the black line. LS labels this chart “RGB Separation”.
Diagram 1. Before: Epson 6020 Pre-Calibration Linearity (RGB Separation)
Diagram 2: After: Epson 6020 Post Calibration RGB Separation (Linearity) using Light Space.
In comparing Diagrams 1 and 2, one can see the huge difference between Epson’s Before and After calibration settings. How does Light Space do this? It’s largely about Pre-Cal projector/display setup and about LS’s proprietary math. LS takes 4,913 hard reads and mathematically extrapolates these to over 32,000 color control points within the LUT cube. Only 1 read per color is done during this calibration phase, which LS calls the Profile Run. They use proprietary math to calibrate, not extrapolate, all the colors in between these 32,000 control points. The proprietary math includes Gamut, Gamma, RGB Separation, RGB Balance and special math to counteract projector/display technology limitations based on years of experience in the field. For eeColor, the 32,000 control points are extrapolated to over 274,000 color control points from which eeColor uses to control all 16.77 million colors of an 8bit color depth projector/display. For the radiance mini3, LS’s 32,000 color control points are used to precisely calibrate the mini3’s 125 (5x5x5) color control points. That’s my understanding of how LS gets the Epson 6020 Color Separation (Linearity), Gamut, Gamma and Color Balance under control.
Now, let’s talk LUT tools. LS can modify the LUT post calibration (the Profile run) in a number of ways. I've used the following: First, the display gamut (i.e. rec709) can be set to be slightly oversaturated, if you so desire, with the Color Space Conversion Tool. Good for well lit rooms. The LS filters can adjust grays to look like grey in the shadows. I use the Relax, Axis Blend, Smooth and Unity Blend filters, when needed. The Relax filter is great to overcome bad meter readings sub 5% … the black shadow regions which are prone to meter mis-reads. Axis Blend, Smooth and Unity Blend filters can correct RGB hue distortions and smooth out luminance “bumps” in the gray scale shadows … depending what works best as viewed by the human eye.
JJEdited by Carbon Ft Print - 12/8/13 at 10:45am