Calibrize is a free visual software along the lines of Adobe Gamma.
If you're good at matching swatches, it is a good place to start learning calibration.
Back in the day, I trained myself to calibrate gamma on the infamous Kodak VCNA (video color negative analyzer) screen with only my eyes and an analog densitometer. Wish they gave degrees for that in the seventies. For the real film industry oldtimers, the legendary Frank Ishihara was my mentor and protagonist.