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NEW TOOL: Calculate Relative Brightness (of Wavelengths in nm)

AnthoT

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500mW of "blue"......? How very specific of you ;)

In all seriousness, the violet comparison is pretty tough to interpret meaningfully, because 405 is right on the edge of our vision and the visibility figures gets incredibly small.
This tool is great and for me its been real accurate except for one thing :p

i can see 100mw of 450 way better then 30mw of 532.. thats the only thing it hasn't gotten right for me.

Other than that this is a great tool RHD! :beer:
 
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rhd

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This tool is great and for me its been real accurate except for one thing :p

i can see 100mw of 450 way better then 30mw of 532.. thats the only thing it hasn't gotten right for me.

Other than that this is a great tool RHD! :beer:
I doubt that.

1) What did you LPM the two lasers on?

2) How do you know the wavelength of the 450?
 

AnthoT

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I doubt that.

1) What did you LPM the two lasers on?

2) How do you know the wavelength of the 450?
It's pretty odd, but I didnt LPM them it was from others but I seriously found the 450 brighter. The green was real bright as well but the blue is just a bit brighter... I have no way to tell the exact wavelength maybe my PL450 is ~460nm but it's bright, the beam is visible without smoke and with lights on as well. And it's set at 220mA...

Here's a photo, no smoke was used at all & it's even clearly visible to my camera

Please excuse the mess in my garage :p
 
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rhd

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Lol, you can't draw a comparison if you haven't LPM'd them.

You might be comparing a 13mW 532 and a 14mW 456, etc.
 

trag

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What you are using when you view a laser beam under subdued or nighttime conditions (but can still tell what color it is), is mixed-mode vision (both rods & cones active).

In this case, the response curve is the combination of both the photopic and scotopic curves! The relative ratio of each will depend on how active each visual system is - the darker it is, the more it will shift away from photopic and towards scotopic.


I have been reading a lot about scotopic and photopic vision lately and I have come to the same conclusion that nighttime laser viewing would fall under the mesopic range. It would be nice if there were CIE measurements for that.

RHD, you were asking about a better source for CIE tables: Luminosity functions. (It's good enough for Wikipedia.)
 

Grix

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You should update this to account for beam diameter as well! Thinner/more concentrated beams appear brighter, right?
 

Blord

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I think it is incorporated in the calculator. It is quite obvious that you don't compare a 1mm beam with a 50mm beam.
A comparison should keep the circumstances equal and only the wavelength is changing.
 
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rhd

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It's incorporated by common sense. That said, I would be open to the idea of adding beam width compensation so that different width beams can be compared to each other.

There needs to be math/science behind it. I won't just assume it scales linearly. It's also a bit of a cop out, but I don't have the time to be part of the conversation that figures it out :( Though I'd code it in if someone gave me the bottom line math :)
 

rhd

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Calculator offline :(. Will it ever be back?
Well - has anyone taken any steps to make a better one?

If taking it down didn't prompt anything better to arise, I may bring it back.

Is anyone working on anything in the pipeline?
 

ARG

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I have looked into reworking it, but I hit a roadblock when I tried to find evidence for the saying everyone uses "4x the power equals 2x the brightness"

I suppose the easy way to fix this would be to remove power comparisons and just compare wavelengths at the same power.
 

zyxwv99

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You should use CIE 1978, not CIE 1931. Look at Seoguy's diamgram (scroll way up). Notice the hump on the left side of the photopic (cone) vision curve. That hump is very real. CIE 1978 has it, but CIE 1931 doesn't.

To see what kind of difference that can make, consider this simple question: You have a 5 mW 532 nm green laser pointer that has actually tested at 5 mW. Now you want a 405 nm violet one that will look just as bright. Question: how much power would it need? According to CIE 1931, 6.7 watts, which is the wrong answer. The right answer is 925 mW, which is what CIE 1978 gives you.

CIE considers their 1931 standard "definitive" for photopic vision (the 1951 standard for scotopic). Everyone agrees that CIE 1978 is way better, but they only consider that a "supplemental" standard. That's because the lumen, an SI unit, is based on CIE 1931. So are millions of light meters built into cameras, not to mention textbooks and reference works for photographers and cinematographers.
 




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