Colour Depth

[Otiman]

How many colours is enough?

256
4026
15536
1.4m
16.7m

I have found a cheap projector which has ~ 4000 colours, not sure if it will suit my needs. (dvd/tv playback)

[blueraja]

4,000 colors will not make you happy. When projecting a tv or dvd image it will result in alot of noticeable dithering. For video games it might be ok but even that will produce banding when the palette extends beyond the color capability of the panel. Personally I would avoid anything below the 1.4m range.

[msx-2]

i think 262k (which is 18bit color) colors is more then enough , especially when the controller is good (don't underestimate its role) look at the benq monitors or the cmv 1512 with the response times of 16ms maximum colors is 262.000 (read it somewhere here).
Some overhead panels have quite good results with only 4096 colors , so if you can get the projector cheap , get it and try it.

[Cybergent]

This question cannot be answered so easy.

First of all it is a question of your personal requirements in picture quality.

I think a real homecinema freak wouldn´t even go near any of these diy-projectors. It is the same with audio. What audiophile person would use a 200$ amp to drive his speakers? None.

So first of all you need to understand, that this will be a compromise anyways. You only have to define on which level this will be. Find out your personal requirements.

To get an idea how colors are coded:
Computers use the RGB pattern with a maximum resolution of 8 bits per color. This results in 256 steps of red, 256 steps of blue and 256 steps of green for a total of 24 color bits resulting in 16 mio colors.

To find out which resolution is acceptable for yourself as a minimum you can try an experiment with Corel Draw:

Just make a box on the screen and fill it with color, that changes from red to green from one side to the other. You can define how many steps are used to change the color. By reducing the amount of steps you reduce the color resolution ie. the color bits visible on the screen.

You will recognize, that with fewer steps you will get visibal discrete levels called banding.

4096 colors in total means 4 bit per color, i.e. 16 steps per colour.
That is really poor.
262144 colors in total means 6 bit per color, i.e. 64 steps per colour.
That may be enough. Just test it.