In the last chapter, we looked at signal testing systems. There’s another kind of testing system that the external monitor needs, called a color calibration system.
The most important color space, common to all the cameras in this guide, is Rec. 709, which is the world-wide standard for HDTV. This space corresponds to sRGB, the universal standard for consumer monitors. Anything beyond this is called ‘wide gamut’. A wide gamut monitor is capable of displaying colors outside this norm.
Note: A wide gamut monitor does not mean it can show every color, just a few more colors outside Rec. 709 (assuming it is the base standard they chose for their marketing).
You’ll find a lot of information on wide gamut color profiles and monitors, and blah blah, but they are not all wide in the same place. Let me explain:
A camera sensor is made of real physical material that interact with light. The resulting electrical signal is sampled via internal circuitry. This process ‘reigns in’ the colors under an established color space, like Rec. 709, while discarding the rest. A good HD camera will have a sensor system capable of producing color far greater than Rec. 709, so that eliminations can be made without penalty.
This is where RAW comes in. By delivering raw, camera manufacturers are giving you the power to choose your working color space. How do you know RAW has more color than a ‘baked’ image? Check out my Dynamic Range comparison of RAW v/s video mode on the Canon 550D article for starters.
Eventually, be it raw or cooked, an image will be delivered to the monitor, and the monitor, being an object made of real atoms and molecules, will have its own color gamut. A wide gamut monitor will usually accommodate most of Rec. 709 (or even 100% of it). It also has ‘space’ for additional colors that one hopes is within the raw file gamut. But who can say for sure?
The above diagram is not to scale, so don’t get too worked up over it. A well designed system keeps things within the ‘ball park’, so to speak.
To know more about color, please read Driving Miss Digital.
Considerations for a good color calibration system:
- As wide a gamut as possible
- Manufacturer must have pedigree
- Ability to discern and study ambient lighting conditions
- Excellent software to make sense of all the color data
- Can work independently
To ensure color accuracy, you will do well to also use the color charts that come with the calibration system.
To test focus, I suggest the LensAlign MkII Plus Focus Calibration Tool.
For white balance, you could use a foam board, or a more robust tool like the Lastolite 12-Inch Grey/White Card:
If you want to check for sharpness, you will also need a resolution chart, like the ones made by DSC Labs. You could print your own copy of the 1951 USAF resolution test chart and its variants, if you want to save money.
One accessory which is a must have for an external monitor is the hood, like this one from Compushade (fits 15″ to 22″):
Always have black cloth handy for those really troublesome days. At least no one will see your tears of joy on achieving the perfect shot.