Re: Let's talk about Lighting
Posted: 31 Mar 2011, 03:05
If you're triggering the camera electronically, you could sync the LEDs and the camera so that you don't have to change the brightness of the LEDs to shoot. LEDs are dimmed via pulse width modulation (PWM) in many cases. If the PWM frequency and duty cycle were based on the shutter speed, the LED would be on for the same duration as the shutter is open, effectively full brightness, even though the LEDs look dim to our eyes.
For example, you decide that 25% is a nice working brightness, and you have enough light at 100% brightness to shoot with a 1/250 sec shutter speed. That means you want the LEDs to be on for 1/250 sec and off for 3/250 sec. 4/250 sec = 62.5Hz. So you need a 62.5Hz PWM frequency (about the lowest that won't give you a headache). At 25% brightness, trigger the camera when the LEDs turn on and the shutter will close when they turn off. This would be a good Arduino or other microcontroller project.
I created a concept circuit, but I need to verify a couple significant details before I post it. I'll try to put that up in the next few days.
For example, you decide that 25% is a nice working brightness, and you have enough light at 100% brightness to shoot with a 1/250 sec shutter speed. That means you want the LEDs to be on for 1/250 sec and off for 3/250 sec. 4/250 sec = 62.5Hz. So you need a 62.5Hz PWM frequency (about the lowest that won't give you a headache). At 25% brightness, trigger the camera when the LEDs turn on and the shutter will close when they turn off. This would be a good Arduino or other microcontroller project.
I created a concept circuit, but I need to verify a couple significant details before I post it. I'll try to put that up in the next few days.