[sudo-discuss] Spectral Response Curves

[Patrik D'haeseleer]

I'm not sure why people are so obsessed by 470nm specifically. If you look
back at the original literature, you'll see that the response is quite
broad, and is actually a fairly good match for the overall blue channel
response you posted earlier.

Compare:
http://www.jneurosci.org/content/21/16/6405/F5.expansion.html
http://www.maxmax.com/images/Cameras/Technical/NikonD200_SpectralResponse.jpg

So yeah, for marketing purposes, it's probably more effective if you can
tap into the hype around 470nm. But if you really want an app that's
effective against insomnia, you might as well measure the blue channel all
by itself...

Patrik

PS: Also, simply subtracting the red channel from the blue gives you such
an incredibly crude measure of the light incoming at any one particular
frequency, that using highly precise measurement equipment to validate the
result is rather nonsensical. The DIY spectroscope Public Lab really gives
you more than enough precision for what you need (although perhaps not
enough for what your customers *want*, but what do they know...)


On Tue, Nov 12, 2013 at 11:50 AM, StCredZero <stcredzero at gmail.com> wrote:

>
> On Tue, Nov 12, 2013 at 11:06 AM, Hol Gaskill <hol at gaskill.com> wrote:
>
>> What's the badwidth you're interested in?
>>
>
> Call me Kenneth, then ask me the frequency. A band around 470nm is what we
> need to detect.
>
>
>>  Shooting from the hip, I'd recommend a photodiode
>> http://media.digikey.com/pdf/Data%20Sheets/Opto%20Diode/ODD-470W.pdf if
>> you just need a coarse signal that detects the band centered on 470nm.
>>  Also, you could use an analog to digital converter or even just a properly
>> dialed-in comparator to cut out the heads and tails of the spectrum.
>>
>
> Not bad for a shot from the hip, but if you read the background, you might
> find it doesn't quite fit the distribution model. Making this out of a
> photodiode and other hardware will make this far less accessible and
> convenient than a smartphone app. The more accessible and convenient such
> measurement is, the more such data will be mentioned in reviews. The more
> such data is mentioned in reviews, the more careful marketers and
> manufacturers will be with measuring their products. (Also, non-maker
> insomniacs deserve good sleep too.)
>
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