Sunday, 20 May 2007

Let there be light

Taking close up video footage requires quite a lot of light because the maximum exposure is limited by the frame rate and zooming in wastes a lot of the light hitting the lens. I have previously been using a random collection of incandescent spot lights totalling about 200w. These gave an overly warm white balance with my camera, a Fuji Finepix 900, plus they tended to get in the way and gave off a lot of heat. I decided to try LED lighting as that seems to be the future. I suspended twelve 1W white LEDs over the top of the machine on a sheet of aluminium laminate plus another six on a strip of copper PCB laminate under the box that supports the Z-axis.

The LEDs were wired in groups of six in series and connected to the 24V supply with a small series resistor. I adjusted these to get about 300ma. A constant current source would have been better but I didn't have any suitable medium power transistors to hand and the supply is well regulated.

Here is what they look like in the machine viewed from below, they are not visible with the normal camera angle from above.

They seem to be bright enough for shooting video and they are only using 18W, 10 times less than my spot lights. If you compare my second video with the first you can see the difference although I didn't have the bottom six installed at that point.

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