Monitor Calibration

 

When we use a computer (windows based, Mac, Linux, etc) we see everything via the computer’s monitor.  Whilst everything might look alright on the screen when creating documents, when it comes down to working with photographs, it can be another matter.

Ambient lighting, where you are working, is very important as it can lead to subtle differences, for example normal tungsten lighting can sometimes produce a slight colour cast, not only when taking the photographs, but later when you are working on them.  So it is important to make sure that the room in which you are working is well lit, not just for obvious health and safety purposes.

Basically there are two types of computer monitor CRT (the older bulky monitors) and LCD (flat screen monitors).

Whilst LCD monitors are becoming more common place, some do suffer from the problem that if it is viewed from an angle the colours do look different.

There are two methods of calibrating a monitor:

1. Visual
2. Mechanical

 

Visual Calibration

Visual involves either using the standard built in tools for setting the screen:

Some will choose to make use of more accurate colour calibration charts, which show a wide range of colours, and different levels of grey, can help detect more subtle colour differences:

Close together lines can be used to check for sharpness of the printer.  In fact the above chart is available for calibrating printers as well.

But visual calibration does rely on the eye of the photographer.

 

Mechanical Calibration

This type of calibration is more accurate, but can be very expensive.

There are tools like the Eye-One which can be used to calibrate both your computer monitor and your printer.

For calibrating the monitor a colorimeter is attached flat to the display's surface, having been shielded from all ambient light, to avoid errors caused by colour casts.

Below is the colorimeter from the Eye-One package analysing the red square on the computer monitor

The calibration software sends a series of colour signals to the display and compares the values that were actually sent against the readings from the calibration device. This establishes the current offsets in colour display. Depending on the calibration software and type of monitor used, the software either creates a correction matrix (i.e. an ICC profile) for colour values before being sent to the display, or gives instructions for altering the display's brightness/contrast and RGB values through the OSD. This tunes the display to reproduce fairly accurately the in-gamut part of a desired colour space.