Problems with projector brightness

“This projector is just too bright” – not something you hear too often at VLOBLIVE gigs!

So is there anything you can do, short of shelling out more cash, to improve the problem of projected live video being too dark.

Before we dive into discussions of brightness, remember that it’s not necessarily about brightness, but actually more about contrast ratio between white and black. Sometimes a brighter projector can have a poorer contrast ratio and look worse! For something like words or powerpoint, you can really boost the contrast on the projector to get it nice and bright, but when you do that, anything that is more subtle, like video, looses all the detail in the shadows and darker areas. It’s almost impossible to get a good balance when you only have one set of controls. You either end up with dull graphics and OK video, or bright graphics and invisible video!! The good news is that there ARE things you can do to improve this situation, without necessarily spending LOTS more money on new projectors etc. Some are obvious, while others may not be. Here are some suggestions: 1. Setting up the video projectors properly always helps. This doesn’t mean ramming the contrast and brightness up to max, as some people believe. I have an article on this subject on my live video website here : Notice, this may mean sacrificing some of the ‘brilliant white’ from graphics etc, in order to save the video. 2. You need to check whether you have your video ‘gain structure’ set up properly. This involves checking the signal levels along the path from source to projector to ensure that when you think you are sending ‘white’ to the projector, what it receives really is white, not light gray. Same for black levels – if you only give the projector dark gray instead of black, you can’t blame it when the contrast ratio is squeezed! Often scan converters or long cables etc, can affect this. Send me a system wiring diagram and I will tell you whether this is likely to be a problem. Best way to do this is with a waveform monitor, or with a DV cam and a laptop with a DV in firewire port. (There is free software you can use to give you a ‘virtual’ waveform monitor) 3. You need to confirm that your sources (especially the cameras) are giving the brightest signals possible. Again are they sending ‘gray’ rather than white? Is their black level set properly? What is their gamma set to? Can you boost the exposure on the camera? Or add more gain? 4. You need to do EVERYTHING possible to keep stray ambient light off your screen. This may mean adding window blinds, fitting barn doors on lights, moving light fixtures, turning some lights off etc etc. 5. The choice of screen material and colour matters a lot. I don’t think you have any screens at all downstairs do you? Again, the lack of a black border, and the matt white wall may not be the best solution. Strangely a mid gray coloured screen material can actually give a better perceived contrast than a white one, especially for low contrast ratio projectors. And apparently putting a black border round the image (as most screens have) makes it look higher contrast. 6. It may help to add a ‘Proc Amp’ box or video enhancer box to boost the darker parts of the video. This is like a standalone ‘contrast and brightness’ control box that lets you adjust the video signal prior to sending it to the projector. This can sometimes give a better balance between the graphics and the video. 7. Can you consider making the main screen smaller? Remember that brightness drops by the square of the area to be covered, so screen size makes a big difference. 8. I know it may be impossible, but moving the projector closer to the screen is always going to help.


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