How many lumens for a 100:1 contrast ratio?

[lotus-eater]

Hello,
I have a 10.4" lcd 640x480 with 100:1 contrast ratio.

I don't know how many colors it has...

I am going to get an overhead projector to project it, and I am wondering how many 'lumens' I should shoot for?

Thanks

 

[lotus-eater]

I am asking this so that I don't get so much that I 'white-out' the image...

 

[henrik_mork]

No danger of that!

Standard minmum is 4000 lumens.
If you buy an OHP that uses halogen bulbs - something around 360W to 400W range would be a good rule of thumb.
If you are wealthy and buy a Metal Halide OHP, the maths is a little less straightforward, but nearly all makes/models would be suitable 5000 - 110000 lumens is likely and the whole range is fine.
If (as it seems) from the spec, the panel is an older type, the TFT panel might be less transmissive than later panels were (that means it lets less light through!) so the brighter the better

 

[lotus-eater]

Any other thoughts?

 

[zardoz]

lotus eater

Given some thought, henrik_mork makes a point...if a lamp is too bright you can take steps to dim it down ..maybe through use of filters or something..if it's too dim you are screwed having no way to "brighten" it up.

zardoz