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eye-friendly camera flash
I quit using electronic flash for my picture-taking because it annoyed people. People don't like flash in their eyes. And, it produces unnatural shadows in pictures. But I needed more light for indoor photography. Not as much as conventional flash – just a little more light.
The problem with flash is the intense light for a short time. So, I got to thinkin', suppose I had a softer light for a longer period of time. Well, it can't be done with electronic flash nor flash bulbs, but it can be done with a light emitting diode (LED). We're still talkin' short periods of time: With electronic and bulb flash, a few thousandths of a second, but with LEDs, a few hundredths of a second.
Light from a LED flash needs less light than electronic and bulb flash to produce the same illumination – a softer light of longer duration. With bulb flash, the method of producing light needs some time before light begins, grows to full intensity, and fades out, so the light is available during only part of the time the camera's shutter is open, providing light for about 13 msec (milliseconds). A flashcube begins emitting light after 5 msec, reaches 75% intensity after 10 msec, 100% at 15 msec, back to 75% at 20 msec, 50% at 25 msec, 25% at 30 msec, and trailing off to nothing at 40 msec. Electronic flash is much brighter for a much shorter period of time.
With LEDs, the full light intensity begins almost immediately, in microseconds, so the light is available during the full time the camera's shutter is open, typically 30 milliseconds, with constant-intensity light. That's about 1/30 second, but can be faster if ambient light is nearly sufficient or slower if more light is needed. A camera with a light sensor can automatically adjust the shutter speed because the illumination appears to the camera just like natural lighting, so the camera can see the light. Therefore, LEDs light the subject with less light and for longer time than electronic and bulb flash so the subject is not blinded with a flash but rather illuminated with a glow. This provides enough light for indoor shots without blinding the subject nor casting shadows.
Furthermore, electronic and bulb flash often produce much more light than is needed. I wanted a flash device to produce less illumination, just enough to get a decent indoor picture. The problem with electronic and bulb flash is critical distance, where the light is adequate for a limited range of distance because an unchangeable amount of light is presented to the camera. Normally, the amount of light taken by the camera is determined by the lens opening and shutter speed. With electronic and bulb flash, the camera surrenders its normal control of light. However, using an LED, the camera retains control because the light supplied by an LED is available for as long as the camera needs. Problem solved: Never too much nor too little light. (Some expensive camera/flash combinations have marginally solved this problem.)
I searched the Internet for solutions and found no commercial product that satisfied my purposes. Found several experimental projects that seemed appropriate while not specifically. The closest project was the ProdMod DIY LED Camera Light Kit designed primarily for video cameras without a built-in light. That project is a bit bulky for my target camera – a Minox subminiature camera. I needed a device in a box about 1/2 by 1 by 2 inches that directly connects to the camera. And, I did not need much battery power since MeekFlash illuminates less than a second at a time, so a tiny battery could survive for years. For power control, I considered VPack, FAN5607, and MicroPuck. However, after much experimentation, I determined these are not required. In fact, those components will absorb some of the power, limiting the power available for the LED. A 6-volt battery of the small size desired can deliver sufficient amperage to drive a 1-watt LED. The voltage of such a battery will quickly drop to about 3.2 volts and deliver almost 300 ma - enough to drive the LED near full power.
Modified Minox Flashgun Model B with LED and battery.