635nm vs 650nm

[oliverst14@hotmail.com]

totally mate

its only the person who took the picture who knows how much of a good comparison it is.
i get that colours can get lost in pictures but i personally reckon the picture is a pretty close match due to me knowing what a 650nm looks like and with people saying a 635nm is pretty orange it looks like what the described.
its a pretty orange colour.

i totally agree with what your saying but as a guide i think it works quite well. maybe its totally off and im really wrong but i think it looks pretty close.

ollie

[sugeek]

so look at my pic - which is the longer wavelength?
is the left hand one lower power or longer wavelength does the colour really show a difference - are they the same? - my point is its what the camera shows isnt really a true representation of the visiblity or the colour.
Rob

My guess (I cheated and looked at the color tones in GIMP) and think that the left may be 650 and the right 635. (ignoring cameras messing up of the true color) I also was guessing due to the "fatness" of the beams the one on the left the straight lines are tiny therefore I assume it is reflecting less light, the one on the right seems wider because more light reflection occurred?

Even better you just used two 635nm lasers to trick us all .

-Adam

[tocket]

Like Rob says, never trust the colors of a camera.

Why? Digital cameras contain typically contain a matrix of tiny dichros to act as color filters. Is it possible to make them to have the same response as the eye? Perhaps, but I doubt it's been done. Here's what you need to match.



On top of that cameras detect photon flux, not radiant power, further adding to the complexity.

Back to topic though, I'm pro 635 now. Because it is far more effective than 650 (which is typically more like 658) you need less of it, increasing the safety of your projector. Having played with 635nm LEDs I think it's a nice red. Sure, the very deep 660 is a beautiful color and saying you have a 7W RGB rig sounds much cooler than the mere 3W RGB needed to match it using 635.

[White-Light]

What you're saying about camera response is right but its also a matter of degrees. It doesn't have to mimic the eye entirely provided its an approximate representation of what the eye would see.

Its easy to get caught up in looking for perfection in response, but provided the camera shows a clear difference that approximates to what you'd actually see then thats enough to give an idea to a potential purchaser. Its much like a paint colour chart.

For me DZ's picture does that. I don't know what camera he used, but it does show the clear differences in colour and brightness albeit if you were to plot the response, it might not be an exact match for the eye.

With your camera Rob, I have to concede, that it doesn't approximately reflect the values and thus wouldn't be of use in the this exercise, in fact I readily admit in your photo I don't know which is which. But I think the answer here is simple, if doing a comparison shot for promo, you'd want to use a camera like DZ's instead. I guess its about selecting the right equipment for the job just as it is when selecting lasers.

[tocket]

It doesn't need to be perfect, but the problem is that most cameras are not even close to accurate. It is most noticeable at the extremes of the visible spectrum (and monochromatic yellow), which is precisely where we find deep red. My cameras even see the IR light from remote controls, which goes to show just how little they can be trusted, because I certainly don't see it.

The camera might, by coincident, show an accurate representation. However, it is sufficiently rare that it should be considered an exception rather than a rule. That is why I never trust pictures when it comes to lasers. It doesn't mean I don't enjoy looking at such pictures though.

[allthatwhichis]

I'm a 660nm man. I want the color pallet and the beam specs. I only need a half watt or so to fully match my blue and green. a 4 diode set up running them nice and low would be perfect, or two running steady with a small 635 with good specs, 100mW or so would be just as good.

Need to get Phillips 3 watt, 24 diode beasty in a projector. With a half watt of 445 and 532... Might need to fatten the blue and green up a tad, but they'd still be smaller than your average 635 beam.

[Showlaser.dk]

Although "brighter", I think 635 on its own is far too orange. Deep saturated colours always look better. I suppose 645 would be a good compromise, expecially as prices are dropping and you can get a reasonably tight (3mm) beam from them.

Who sells those 645nm diodes (bare diodes or modules), and how high powers can you get them in ?
Sounds like a good compromise.. i was planning to combine 635nM and 650nM for my RGB system.

Thanks!
Regards, Simon

[White-Light]

I think 645nm is a gas laser exclusive!

A look at the CNI website shows 635 and 655 in Diode lasers and 593 and 660 in DPSS.

No-one makes a 645nm diode at the moment.

[QUAZAR]

Sorry for the typo. Should be 642nm.

http://photonlexicon.com/forums/show...ighlight=642nm

[DZ]

My guess is the one on the left is the longer wavelength. My guess is based on the fact that the one on the left has a smaller beam profile hitting the screen.

Regarding my pic, I took that photo probably 2 years ago. I remember it looking almost the same as it turned out in the photo. And you can't get around the fact that the ratio we came up with of 4.5-5 to 1 was agreed on by about 4 or 5 people at two seperate FLEM meets. We displayed an identical abstract on two different projectors and set them for what everyone thought was the same aparent brightness, then measured the output power on both projectors. I *think* it ended up being around 375mW from a Maxymodule and 75mW from a Lasever.

For the record, the camera used is a Sony Cyber-Shot DSC-W1. An amazing little camera, the counter on it just passed 9000 a few weeks ago!

so look at my pic - which is the longer wavelength?
is the left hand one lower power or longer wavelength does the colour really show a difference - are they the same? - my point is its what the camera shows isnt really a true representation of the visiblity or the colour.
Rob