The_Driver
Flashlight Enthusiast
Re: Phosphor conversion of photons in LEDs
I haven't gotton into lenses yet in the simulations. It might take me a while.
The equation has been proven many times over. The important thing here is that it can be applied from the Candela measurement back to the light. The lens can't be any bigger than 36mm if that is the diameter. You can't "cheat" this system.
I don't believe the 260kcd number with the current information regarding this light. It could be inaccurate for a number of reasons:
The Osram Black Flat is sold in different Bins, but you never know which one you get and even then there is a high variance in performance between different LEDs. Maybe vinh got LEDs from a reel with a very high bin which nobody has tested before. Is his 260kcd the average of all his lights or the best one he measured?
Has anybody confirmed this value (measured in a reasonable distance) and also measured other ANSI-specified, unmodified lights with the same setup?
With the standard equation using 250cd/mm^2 and 92% transmission I get 234kcd for a 36mm lens. That's only 10% less than vin's value. It's not really possible to draw any conclusions from that. It's easily in the same ballpark.
You know, thinking about it, vinh sells a ton of lights based just on their luminous intensity. He really should be using a calibrated, high-quality luxmeter for his measurements (i.e. Gossen Mavolux, Mobilux etc.) and always comparing them with unmodified lights. He is a professional after all.
I haven't gotton into lenses yet in the simulations. It might take me a while.
The equation has been proven many times over. The important thing here is that it can be applied from the Candela measurement back to the light. The lens can't be any bigger than 36mm if that is the diameter. You can't "cheat" this system.
I don't believe the 260kcd number with the current information regarding this light. It could be inaccurate for a number of reasons:
- It's very, very difficult to get accurate optical measurements, 10% would be very good
- The accuracy of a luxmeter always needs to be considered
- Cheap luxmeters have problems with wavelengths at the edges of the visible spectrum (blue and red light) because of the shifted bell curve of their filters
- The Osram Black Flat has a high content of blue light in it's spectrum, so the varriance between the values measured by different luxmeters should be higher compared to greenish de-domed Cree leds
- Is 36mm really the actual optical diameter of the aspheric lens in this light? Does it have a coating? What type of glass is it made of?
The Osram Black Flat is sold in different Bins, but you never know which one you get and even then there is a high variance in performance between different LEDs. Maybe vinh got LEDs from a reel with a very high bin which nobody has tested before. Is his 260kcd the average of all his lights or the best one he measured?
Has anybody confirmed this value (measured in a reasonable distance) and also measured other ANSI-specified, unmodified lights with the same setup?
With the standard equation using 250cd/mm^2 and 92% transmission I get 234kcd for a 36mm lens. That's only 10% less than vin's value. It's not really possible to draw any conclusions from that. It's easily in the same ballpark.
You know, thinking about it, vinh sells a ton of lights based just on their luminous intensity. He really should be using a calibrated, high-quality luxmeter for his measurements (i.e. Gossen Mavolux, Mobilux etc.) and always comparing them with unmodified lights. He is a professional after all.
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