How Good Are LED's

 

Well, that all depends on the types of leds that you buy, and what your applications are. How far an LED will spread from it fundamental frequency is determined by current, heat and other factors in manufacture.

My concern for the spectrums of LEDs came when I trying to make a darkroom safelight that could be battery operated for long periods of time. The color was looking for was a yellow cast color as not to expose my paper. Photographic paper which can be exposed by green wavelengths and higher, but much less sensitive to yellow and red colors. LEDs came to mind for their robustness and low current consumption, and single wavelength of color.

Much to my chagrin the yellow LEDs that I used immediately exposed my photographic paper.

What could be going on they looked yellow? The same type of yellow that my trusty kodak safelight produced. Something that I was doing was wrong.

I have posted here some sample spectrums of some el-cheapo leds. The way I obtained these pictures is using a ordinary DVD or CD as they will diffract the light into its basic components, play around with this it is a very neat trick to determine what colors really compose a light source.

Very good Red LED								El Cheapo Red LED
				

El Cheapo Yellow										 El Cheapo  Blue LED
				

White LED


What can be deduced from these pictures is that all leds are not made equal. they may say yellow but they really mean a little green, a lot of yellow, and a bit of red. Not quite the single wavelength that we were looking for. No wonder they exposed my paper!

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