Biological reasons for color perception

[Dr_Evil]

If we measured more light sources in lumens the world would be a (slightly) better place. For instance: vehicle headlights. If the maximum output was in lumens rather than watts then people couldn't play with the color and blind other drivers.

That has to do more with the aiming of the headlights and housing design. I could put a crappy 25w bulb in a housing improperly aimed and blind somebody. Or I could put a 85w bulb in a properly aimed housing and not blind somebody. A lot of the idiots blinding oncoming driving put HIDs in housings design for normal halogen bulbs. I think it is also possible to mess up the output using a different brand of HID bulbs used in a housing designed for a certain brand of bulbs. I'm not 100% sure about that though. I don't think the position of the light source is the same for all brands.

 

[Ablaze]

Thanks for that madmac. That was the site I was looking at before, and it still doesn't show a way to calculate Vλ.

And now that I take a closer look at that table that rhd uses I can see that it is basically a table of different values of Vλ at different wavelengths. So I guess that may answer my question, thanks again.

Does anyone know who this Ben Steigerwald (who claims ownership of the data in that table) is?

Unfortunately, I've been using that tool for a while now, and I've found it to be inaccurate for 450nm lasers. Perhaps in 1924 when they collected this data they just didn't have a good way to produce 450nm light? Or perhaps they made a mistake...

 

[Sigurthr]

Ben Steigerwald is/was a laser hobbyist I knew a few years back. He ran ************. Before my hiatus from the laser hobby I was a very active member on that site, and I seem to remember helping with some of the site design aspects.

Lost touch with him though and no idea if he is still active in any form.

 

[Ablaze]

Yeah, I noticed that it only goes up to 680 as well.. but I figured a 0.44% difference wasn't enough to worry about.

The problem I have is that I own these two lasers: Green 5mw and Blue 25mw and in reality they are approximately equal with the blue being perhaps slightly brighter.

 

[Ablaze]

:shhh: It's not the beam characteristics that make it different, it's the chromacompat=yes flag, which makes it use a different table than the one in the link.

here is your 115 w/o chromacompat

The chromacompat table seems to be closer to reality, but there is no link to it. Both of them are WAY off when it comes for 450nm.

 

[qumefox]

The chromacompat table is the same one chroma uses (color mixing software, available on PL. just search for it.) Hence the name.

The problem that arises here is that apparent laser brightness is trying to be converted to a measure that's ill suited to describing it.

The problem boils down to the fact that a lumen is a spherically integrated measurement, and it's exceedingly difficult to use that method to measure a light source that in essence would end up a point of light on an integration sphere. Even changes in focus would change the luminous power readout.

This is why the numbers aren't right. There isn't really any math to get from A-B accurately with this.

It's like using ft-lbs of torque to describe how fast a car goes..

 

[Ablaze]

It's like using ft-lbs of torque to describe how fast a car goes..

If that's the case than mw to describe brightness is like using decibels to describe how fast the car goes..

I just think there is a massive need for a more descriptive scale of laser brightness.

Maybe I'll make one up.

 

[lasersbee]

"we don't need no stinkin' brightness"..... :crackup:

Jerry

 

[qumefox]

The Watt has been used to describe optical power in lasers since the 60's. Not sure why exactly you feel that it should be changed now.

The reason there isn't a way to quantify 'brightness' in lasers is because it's a very non-quantifiable measurement.

How 'bright' something is is very much subjective from person to person and eyeball to eyeball. For 'wide area' sources like light bulbs, It can be quantified by luminous flux over an area (what integration spheres do) This is hard to do accurately for a laser due to the miniscule area of the beam. Coupled with the fact divergence and focus are going to change the numbers a lot even for the same power and wavelength laser.

If you can come up with math that can quantify 'brightness' based on wavelength and power that actually works, more power to you. however there are many many roadblocks to this.

One of the biggest being the non-linear nature of vision. 2W doesn't look 'twice as bright' as 1W for instance. This is actually likely where the current math fails. It assumes 'brightness' is linear, which it isn't.

 

[Ablaze]

Hold your horses qume. I'm not attacking your current method, and I'm certainly not attacking you. Please keep that in mind when I say this: I think you are too familiar with the watt as a unit of measurement to see its awkwardness for anyone who has not spent at least a month getting used to it.

The mw is just not a unit that intuitively clicks for anyone who is not intimately familiar to lasers. I really don't think that brightness is as subjective as you say either. I think that the slight subjectivity is a solvable problem, after all they solved it for lumens.

I think you are right: To make a very good scale you might have to use brightness, wavelength, and divergence. However, you wouldn't have to measure for the entire range of possibilities, at least not at first. You could just measure the 10 or so most common laser colors.