What is the best way to calibrate a monitor ?

First, you will NEVER get coloring to be the same across all monitors that will playback your videos. So don't sweat that much.

The only way to get true coloring readouts is with a broadcast monitor via SDI connection.

macOS has a pretty decent built-in calibration tool (System Preferences > Displays > Color), I'd recommend you use it to start with.

Hardware calibrators are not all that cheap, but I guess would be worth the try.

The advantage of Apple's own monitors is they use the ColorSync technology to automatically calibrate and keep things on an even keel. Third party monitors may require calibration. But computer monitors and TVs won't give you 100% true color representation like an actual broadcast monitor will.

An actual broadcast monitor, like from Flanders Scientific and others, needs an SDI input. You'd have to use a box from AJA or Blackmagic Design that converts from Thunderbolt or USB to SDI. This gives you a pure signal, no filtering.

Most all computer monitors and TVs have built-in filter systems that automatically try to optimize the image they're displaying. You can't turn them off.

To see an example of this, go to a Best Buy, look at that wall of HD TVs, and they all have different color and hue characteristics. Even if you got the remotes to two of them side by side, and play with the color, brightness, etc, settings you'll never get the two to look identical.

A broadcast monitor is a whole different animal in a whole different universe. Even HDMI connections are two-way connections, and risk one device altering the image based on the other device's feedback. It's got to be SDI no a calibrated broadcast monitor.

Hi thanks for the reply ....Do you have any idea what is there in a broadcast monitor that makes it so much more accurate than third party monitors ..... ? which technology ?