[sdiy] calculating resistance to match brighness across different colours of leds?

[Scott Nordlund]

The eye is more sensitive to green, but I don't think it would be very easy to tell which is brighter just by looking at it.

Maybe you could combine the light of both and adjust for a reasonable yellow color.

----------------------------------------
> From: julian at port23.co.uk
> To: synth-diy at dropmix.xs4all.nl
> Date: Wed, 25 Mar 2009 01:04:41 +0000
> Subject: [sdiy] calculating resistance to match brighness across different colours of leds?
>
> Hello,
>
> Rather than doing it 'by eye', i thought it was about time i should do this properly -
>
> I have two leds, a red and a green. The specs are:
>
> Red:
> Wavelength: 700
> Lum. int. (mcd) @ IF (20mA): 10
> IF max. (mA): 15
> VF typ. (V): 2.2
> VF max. (V): 2.8
>
> Green:
> Wavelength: 570
> Lum. int. (mcd) @ IF (20mA): 30
> IF max. (mA): 30
> VF typ. (V): 2.1
> VF max. (V): 2.8
>
>
> If i use a 10k resistor on the red led, and i want the green one next to it to be, to the observer, the same brighness is this just
> a simple cacluation?
>
> Im concerned that it may not be simply a case of matching the luminosity - i dont know, but does the human eye (assuming a 'normal'
> individual) have equal sensativity across the visable spectrum?
>
> Im thinking of how the ears are more sensative to treble than bass... (?)
>
>
> Julian
>
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