Hello Dr. Jolyon
I would like to know how we can measure the reflectance values of the grey cards.
How to measure the reflectance of a grey card
jolyon Answered question November 16, 2024
You’ll need to measure this against a known standard (e.g. spectralon 99% standard, or a flattened/compressed pile of barium sulphate (which is pretty close to 99%, and is at least repeatable).
Take a photo of your grey card next to this known standard. Calibrate this image using the known, and then measure the unknown in this image.
Be careful to ensure the lighting is perfectly uniform between standards (and your own shadow isn’t causing interference). Natural daylight in an open place is going to be better than any lab lighting unless you really know what you’re doing.
How to measure the reflectance of a grey card
jolyon Answered question November 16, 2024