low-absorbance white paint for indirect lighting

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low-absorbance white paint for indirect lighting

Postby brötchen » Sat Feb 12, 2011 1:11 pm UTC

So I'm thinking about building an LED based lamp for my room but since LED's tend to be fairly pointy light sources i want to build a indirect lighting system.
The Problem I ran into is that there is little to no data about the absorbance spectrum of standard wall paint, which would be used as the diffuse reflector surface for the indirect lighting system, and special high reflectivity paint, like the stuff used in integrating spheres costs several hundred bucks per square foot. so where do i get numbers on the absorbanc of different types of paint?
or does any of you have recommendations on what type of paint to use for a project like this?

Also excuse my bad English, I'm not a native speaker.

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Re: low-absorbance white paint for indireckt lighting

Postby iChef » Sun Feb 13, 2011 6:12 am UTC

I've found plain white flat paint to be fairly good at reflecting light. You get the best value for your money. Specialized paints or reflective materials can get expensive fast. Although most of my experience comes from building indoor gardens, so I am working with fairly intense light sources to begin with.
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Re: low-absorbance white paint for indireckt lighting

Postby idobox » Mon Feb 14, 2011 8:59 am UTC

One of the best white pigments is titanium oxyde, and it is widely used in paints for buildings. It is often branded as titanium white.
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Re: low-absorbance white paint for indireckt lighting

Postby Hemmers » Mon Feb 14, 2011 1:21 pm UTC

I think you're probably overanalysing the issue. Unless you need specific light levels for a specific science or photography project, then any matt (i.e. non-glossy) white will do - Titanium White is good as mentioned above.

Here in the UK, most indoor rifle ranges use a simple clean matt white on walls, ceilings and sometimes floors. It's cheap (even a 25yd range is a lot of square footage) and quite effective (we're usually trying to get as close to daylight levels as reasonably possible all the way downrange and on the targets).

A gloss would be more reflective but obviously for a shooting range you don't want excessive glare as that will ruin your sight picture. Depending on what the light source will be doing and where it will be, you might want to go with gloss, but a matt finish won't give you specular reflective points.

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