Laser pointer Rayograph
Red laser pointer, Instax Wide format film. Odd how the laser at its brightest turns out blue. Anyway; how did I do this?
1. Put instax camera with film already in it, and laser pointer in lightproof changing bag having noticed how many shots you have left.
2. Zip up. Take off watch that glows in the dark!
3. Put arms in arm holes, locate camera and take out film pack.
4. Orient film pack correctly (sensitive area facing up).
5. Place laser pointer on film, switch on and guess-draw some sort of "interesting pattern".
6. Switch off laser pointer.
7. Replace film pack in camera.
8. Unzip and remove all articles from changing bag.
9. Switch on camera and press shutter to release/develop photo; the camera thinks the image is the darkslide that protects the film pack.
10. Marvel at the unreal colours.
11. Scan and post on Flickr for worldwide admiration.
I asked "an expert" why the red laser was turning up blue here and he said this:
"If I had to guess I'd speculate that this is what's going on. Film
emulsion contains three different sets of chemicals (possibly in
separate layers ?) which deal independently with the red, green and blue colours. The laser is monochromatic - it only emits red light - so you'd think that the blue and green processes would never get activated, and in general that's what we see. At very low intensities the red process works as we would expect and we get the nice red parts of the picture."
"At higher intensities we "burn out" the red process (the laser beam will be quite sharp-edged and the intensity where the black central line is could easily be hundreds of times higher than in the red surrounding region). Let's say ordinary low-intensity light turns chemical A into chemical B and it's chemical B which makes the red colour when it's developed. Too much red light turns B into some other chemical - say C, which doesn't develop to red. Or perhaps it produces an additional chemical (D) which somehow poisons the developing process. In any case we get burnout."
"The appearance of blue in some places will be something different again. It won't be the laser intensity which is varying (intensity is power per unit area and the laser power and beam size will be constant). The blue spots probably appeared where the artist stopped moving the laser beam for a few seconds. Holding a fixed intensity beam still will cause the local temperature of the emulsion to rise and it may be that it's the heating which is triggering the "blue" chemistry. Or, perhaps, there's some leaching of the copious amounts of chemical C (or D) from the heavily saturated red process into the blue layer ? But now I really am guessing."
"The one thing I can say is that there's unlikely to be any blue light involved. In principle it is possible to add two red photons together to make a blue one but this process (called "nonlinear optics") usually requires intensities many orders of magnitude higher than you can get from a hand-held laser."
Laser pointer Rayograph
Red laser pointer, Instax Wide format film. Odd how the laser at its brightest turns out blue. Anyway; how did I do this?
1. Put instax camera with film already in it, and laser pointer in lightproof changing bag having noticed how many shots you have left.
2. Zip up. Take off watch that glows in the dark!
3. Put arms in arm holes, locate camera and take out film pack.
4. Orient film pack correctly (sensitive area facing up).
5. Place laser pointer on film, switch on and guess-draw some sort of "interesting pattern".
6. Switch off laser pointer.
7. Replace film pack in camera.
8. Unzip and remove all articles from changing bag.
9. Switch on camera and press shutter to release/develop photo; the camera thinks the image is the darkslide that protects the film pack.
10. Marvel at the unreal colours.
11. Scan and post on Flickr for worldwide admiration.
I asked "an expert" why the red laser was turning up blue here and he said this:
"If I had to guess I'd speculate that this is what's going on. Film
emulsion contains three different sets of chemicals (possibly in
separate layers ?) which deal independently with the red, green and blue colours. The laser is monochromatic - it only emits red light - so you'd think that the blue and green processes would never get activated, and in general that's what we see. At very low intensities the red process works as we would expect and we get the nice red parts of the picture."
"At higher intensities we "burn out" the red process (the laser beam will be quite sharp-edged and the intensity where the black central line is could easily be hundreds of times higher than in the red surrounding region). Let's say ordinary low-intensity light turns chemical A into chemical B and it's chemical B which makes the red colour when it's developed. Too much red light turns B into some other chemical - say C, which doesn't develop to red. Or perhaps it produces an additional chemical (D) which somehow poisons the developing process. In any case we get burnout."
"The appearance of blue in some places will be something different again. It won't be the laser intensity which is varying (intensity is power per unit area and the laser power and beam size will be constant). The blue spots probably appeared where the artist stopped moving the laser beam for a few seconds. Holding a fixed intensity beam still will cause the local temperature of the emulsion to rise and it may be that it's the heating which is triggering the "blue" chemistry. Or, perhaps, there's some leaching of the copious amounts of chemical C (or D) from the heavily saturated red process into the blue layer ? But now I really am guessing."
"The one thing I can say is that there's unlikely to be any blue light involved. In principle it is possible to add two red photons together to make a blue one but this process (called "nonlinear optics") usually requires intensities many orders of magnitude higher than you can get from a hand-held laser."