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Difference in brightness?
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Difference in brightness?

by jons3657 on Wed Sep 04, 2019 12:14 am

Hi there,
I've heard that there's a difference in brightness between the regular sized neopixel strips and the "skinny mini" neopixel strips, but I couldn't find any information on brightness in the technical information. Is there any difference in the brightness? Thanks!

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Re: Difference in brightness?

by adafruit_support_mike on Thu Sep 05, 2019 4:06 am

We aren't aware of any specific difference, but there are a lot of variables in play.

First, perceived brightness is hugely subjective. The human eye responds to ratios of photon density more than to absolute levels, which allows us to see in moonlight and under noonday sun (an absolute variation of about 10 million to 1). On the other hand, headlights that are barely visible during the day are blinding at night.

There are also geometry issues.. almost all indicator LEDs are designed for a nominal 1000mcd of luminous output, but you also have to look at the way the light is arranged. 'Luminance' counts the number of photons emitted, but 'illumination' counts the number of photons that hit a 1m^2 spherical surface located 1m away from the source.

An ideal point light emits the same amount of light in every direction, so 1000mcd of light gets distributed across about 12.6 square meters of a sphere whose radius is 1m.. the illumination is only about 80mcd per square meter.

A standard flat NeoPixel emits light in a cone whose angle is about 120 degrees, which means the same 1000mcd would get distributed across an area a little larger than 1 square meter, and the rest of the 1m-radius sphere would be dark. The illumination in the region the light hits is about 12x higher than you'd get from an ideal point source, even though the LED emits the same amount of light.

Taking that idea to the logical extreme, you get lasers.. highly collimated light that puts all the photons in an extremely small area, making it possible for the equivalent output of an 80W light bulb to cut plastic and etch metal.

The mini-skinny NeoPixels are smaller than standard NeoPixels, so the well that reflects light out into the 120-degree-ish cone is smaller. That means its surface area is smaller, so the illumination on those surfaces will be higher even though the amount of light from the LEDs is the same. You wouldn't see much difference in the illumination on a sheet of paper 1m from a standard NeoPixel or a mini-skinny NeoPixel though.

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Re: Difference in brightness?

by jons3657 on Fri Sep 06, 2019 12:51 pm

What I meant was, "is there a difference in lumens between the regular neopixel strips vs. the skinny mini neopixel strips?"

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Re: Difference in brightness?

by adafruit_support_mike on Fri Sep 06, 2019 9:29 pm

No, they're both spec'd for about 1000mcd poer LED.

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