Color Analysis

[BobJ]

We are doing a series of talks on theater lighting to Students in our smaller, Pavilion theatre. One of the subjects will be the spectral emissions produced by legacy (Tungsten) and LED lights, both simple RGB and RGBWA.

What I would like to be able to do is shine a lamp unto a white surface to demonstrate the effects of colored gels and for the LEDs mixtures of RG&B. What would be very effective would be to see a visible spectrum scan that would change as, say the RG&B percentages were altered in the mix.

 

I have seen some very expensive spectrum analyzers on the market but was wondering if there wasn't anything (software based and using a tablet's camera perhaps) that was around for a whole lot less. There are of course a huge number for the audio frequencies but I would have thought lighting engineers/techs/designers would like a way to assess a Lamp. GEL, LEDs color composition. Ideas?

[timsabre]

I don't think it would be possible to display a spectrum using a camera since the camera just has r, g, b sensors. The best you could do would be to show 3 values for r,g,b.

 

There are a couple of android apps which will display a spectrum graph if you split out the spectrum using a diffraction grating. Have a look at the app "aspectra mini".

[Jivemaster]

I did once see diffraction gratings on a film mounted in 35mm slide mounts. Very easy to pass round for people to look at different sources. Alternatively you need a glass prism and set up to produce a spectrum and look for lines.

[Shez]

There are some photography light meters that will show you the spectrum, including some not unreasonably priced units that just Bluetooth to your phone.

[timsabre]

I couldn't find anything that cost less than £1500 - what do you call "reasonably priced"?!

[kitlane]

There are some DIY projects that use an old CD and a cardboard tube to make a crude diffraction grating. A quick google search should reveal some almost-free options. Maybe the students could make their own?

[Shez]

I couldn't find anything that cost less than £1500 - what do you call "reasonably priced"?!

I must be going mad - I distinctly remember looking at a product a few months back that was perhaps around the £300 mark. Unusual design - perhaps shaped like a pyramid. Can't for the life of me find it now though!

[paulears]

Could you use a vectorscope? Not sure quite what would happen if you opened say, the one up in premiere and fed it a live video camera signal? I've never tried it, but if you can find a physical vectorscope you can feed video to, that should give you a good indication of what is going on.

 

EDIT

 

I found an interesting app - mavis pro camera, there's a vectorscope and there's all sorts of waveform monitors. I have no idea if it's accurate enough for your purpose, but worth a go.