When calibrating a screen which is fed by a PCIe card such as a BMD mini monitor, does the calibration software adjust only the settings in the BMD card to compensate for the screen?
I have to ask that just to make sure I understand the process.
No worries. Here's how it works:
The mini monitor gets the image signal from Resolve directly, without any color adjustment from the OS. The mini monitor converts the signal to HDMI and SDI without altering the color. This signal accurately represents the data coming out of Resolve. So the signal is good, but your monitor isn't neutral.
That means when the signal sends a pixel that is 100% pure white, your monitor shows a pixel that is not. It may be a little green, or a little magenta, or a mixture of several colors. We call this inaccuracy a "bias." Every monitor is biased uniquely, so each monitor must be corrected to neutral individually. Correcting the bias to neutral (so the color from the signal is displayed accurately on the monitor) is called "calibration."
To calibrate, you need an accurate signal going into the monitor (the mini monitor does this), a known color source to test the monitor, a sensor to read the known colors from the monitor, and calibration software to measure the bias based on the innaccuracy of each color sample.
An inexpensive solution is to buy an x-rite i1 sensor, and use dispCalGUI, a free open-source calibration app.
dispCalGUI works with Resolve to generate known color patterns, which the sensor reads and sends to the dispCalGUI software for analysis. When the sensing is done, the calibration software analyzes the samples and figures out the specific bias pattern of the monitor. The app then creates a color look-up table (LUT) that reverses the exact bias, rendering the monitor neutral.
You export the LUT after calibrating, and then load it for output from the mini monitor. So the pure signal from Resolve is being biased in exact reverse of the bias of your monitor. When your monitor shifts the color, it now displays the actual true signal colors, because the calibration LUT has offset the monitor's bias.
Since monitors shift color over time and due to environmental conditions, it's a good idea to recalibrate on a regular basis. Low-volume shops usually calibrate before each big show. High-volume shops calibrate on a regular interval, but not in the middle of a job.
Hope that clears it up a bit.