LCD Specification and buying

[DionM]

Edit: I just edited this post - too big!

Anyway, a couple of questions when buying LCDs.

- 16.2m vs 16.7m colours. Some have told me that a 16.2m colour panel may suffer from dithering artefacts. True or False?

- DVI vs D-Sub connections. Obviously DVI is the latest tech, but is it 'essential'? I am looking at a dual 17" (or dual 19" if I can afford it) setup and this may mean entry level monitors - which only have D-Sub connections.

[Jesper]

Short answers: Do NOT buy and LCD screen that says "16.2 million colours" if you're serious about using it for image editing. And yes, DVI is worth it.

The explanation:

Good monitors can display 16,777,216 different colours: they display 8 bits per colour (red, green and blue), which means 2^(3x8) = 16,777,216 colours or 16.7 million colours. There are also cheaper LCD panels that can only display 6 bits per colour, which means they can display only 2^(3x6) = 262,144 different colours. With the help of a trick (dithering) they simulate other colours. Those screens are often marketed as "16.2 million colour" screens. When you use such a screen for viewing photos, you're likely to see problems like banding in smooth surfaces of photos. Such screens are simply not suited for serious photo editing.

Computers and LCD monitors are digital devices. CRT monitors are analog devices. The D-Sub interface was made for CRT monitors: it's an analog connection. The video card in the computer converts its digital signal to an analog signal and sends it to the CRT monitor, which can display it directly. When you connect an LCD monitor with a D-Sub connector, the computer does a D/A conversion and the LCD screen has to do an A/D conversion to make the signal digital again. Those conversions cause a loss of quality, which means the screen will look less sharp. DVI is a direct digital connection, no conversions necessary, and no loss of sharpness. I especially bought a video card with DVI when I got my LCD monitor (a Dell 2405FPW).