how to light using a data projector

[sherwin]

Hi APUGers,

I'm shooting some portraits tomorrow and for one of the photos I want a hard key light hitting the subject front on. Due to limited resources and a short time-frame I'm thinking of using a data projector projecting a white frame. My two concerns are 1. brightness and 2. colour temperature. I'm shooting on 400 speed daylight balanced 35mm colour neg.

It's a 2000 lumen projector and I can afford to have it as close as 2 metres from my subject. Will I be able to capture bright, hard light?

I don't know the exact model number for the projector yet so haven't been able to look up the exact colour temperature, but if it's something like 5000-7000k will my whites be white? If i discover that the colour temperature is something like 4000k can I simply project a pale blue image to achieve correct white balance?

Cheers,
Sherwin

 

[David William White]

"front on"? They will be squinting and cursing you. With 400 speed film, why not just go outside and use the sun?

 

[sherwin]

the photo is part of a triptych set in the same location and I need control over light. In the other two photos, the light is soft, almost dark and I don't have the resources to filter the sun to this extent. I wish I could though!

 

[nickandre]

digital projector? not sure, you can change the color temperature depending on what you display. if you have a polaroid, try it out. if you have time to process film, try that out. compare it with daylight, compare it with a lightbulb. use a digital camera to confirm, one with fine tuning white balance in Kelvin.

analog projector? uses a halogen bulb, use an 85B or whatever.

 

[sherwin]

thanks tiberiustibz,

it's a digital projector. I do have access to a digital camera so i can set white balance
to 5600k and project a range of yellow and blue shades through the projector until I hit the desired colour temp

cheers

 

[holmburgers]

Regarding color temperature of the projector, you need to know what kind of bulb it uses. I'm not familiar with them really, but I would guess that it'll be overtly blue. TV screens, as I've found out, are quite blue to film, when it looks grey to the eye. However, with a flat-screen computer monitor, which uses fluorescent back-lighting, it comes out rather green.

Now you say "If i discover that the colour temperature is something like 4000k can I simply project a pale blue image to achieve correct white balance?". I think the answer is maybe. By changing the image that you are projecting, you're really just changing the proportion of each red, green and blue "pixel". You are not fundamentally changing the color of the illuminant. However, in theory I think it should work, assuming it's a continuous light source.

Find out what kind of bulb it uses.