Blue laser 445nm

[dar303]

Please do! Take something really massive that you like yourself!

[chad]

The sheer number of fixtures is totally impressive. However, the synchronization kind of sucks.
However, I've been there, seven hours into a rave show. Either you are too hammered to care or you just don't care anymore, and autopilot takes over.

the live stuff just isn't quite there yet. The problem with laser is it's difficult to do stuff 100% on-the-fly. There still isn't any good truly on-the-fly abstract generator available. I started writing one about 10 years ago for the first pangolin board but it was still tough to do things live on fly.

But like I said, the sheer number of fixtures is simply stunning. Being in the US we can get away with that if we want to. I totally envy those in Europe who can experience this sort of thing live.

Personal comment.
I personally am a old-school break beat type of guy. And I classify that music as CD skip. But a bump, a bump a bump, gets fatiguing fairly quickly and it is easy to run out of things to do with lighting or laser. but I am still totally envious of you lucky Europeans. I have had similar setups in the garage, but I just can't do that legally here in the US.

Chad

[Pitts]

HI Guys,

Can I raise this old thread of mine again.. a couple of months have gone by since this was discussed.
I still see lots of advice to newbies with the usual formulas being trotted out.
It also seems to me that we are in a time of change "again". Its no use talking of "red" or " blue" anymore. I guess we can still talk about green OK as that still seems settled on 532nm.

Pretty hard now to say X% red X% blue with X% green..

Reds are now in a range plus or minus their various "issues"...
common are 635, 640, 650, 660, 671..
Blues are the same 405, 445,457, 475 etc

Add to this ( I have never seen this discussed in any depth the "fat" beams and how much of the fat beam is "mixed" to get to the "white") its a bit like an unwanted relative no one talks about it much.
It seems that most don't even take it into account and still say its part of the "white " light... beats me, if 50% of the beam is sitting "outside" the mixed beam because it too fat how can you count that % in terms of the "white" power. No I am not looking for an argument !! just an observation maybe someone has some ideas..

Anyway I digress. Back to "modern" solid state color mix problems.

I have bitten the bullet and have 640 nm 900mw red on its way.

I have a 500 mw green to go with it.

I would appreciate some feed back on the blue... currently have 250mw 475nm however if I am seeing thing correctly I would be better with a 445. If so how much power 500mw ??

Given that you cant trot out the "standard" formula at these wavelengths it would appear, ... any ideas..??

Looking at Tockets chart he did a while back the 445 facts seem to support the Arctos and now Kvant statement that 445 is a "peak" sensitivity for blue.
If you look at Jem's link above it shows this very well.

So .... get 445nm at say 500mw and mix with 475 or just forget the 475 (which would suit me as can make another unit that way.)
A one watt 445 is available just the mortgage isn't...

Any feedback would be appreciated.

Cheers

Ray
NZ

[The_Doctor]

By power you mean radiant power, right?

Well, it only takes 8mW of 532 to make 1W of 650 look like 635 (6mW for 658). Adding that little green isn't going to make a big difference to the luminance or brightness. For 650 you gain 7% in luminance and for 658 8%. Considering the 635 has 3 times the luminance compared to 1006 mW of 658+532 it really does seem like 635 is the better choice.

That's the most compelling argument yet, it accounts for what Aijii and Dave kept telling me when I used to argue that longwave reds were better for colour gamut (that there is no noticeable difference when mixing colours, if you use 635 instead of 650). Thing is, it is also true that 650 does increase gamut, so, if a person DOES want that strong deep gamut then maybe it means a change is needed in the DAC. Perhaps an antilog amp on the output or something. Looks like the subtlety in the low end of the amplitude scale is more important than the high end. As far as I've seen, most systems are linear, at least, the analog input of a laser I used to have was.. And with a 12 bit output, software curve shaping isn't going to be enough to do it. As I read recently that a simple analog log amp can make a 12 bit ADC take a useful and accurate dynamic range equivalent to TWENTY bits, then an antilog on the output might make better meaning for the small differences of amplitude in colour mixing. Not for the budget priced show gear though... Those linear amps cost £10 or more alone, never mind the extra cost of strong lasers...

[tocket]

What chart? I've made so many now I feel I should start numbering or otherwise label them.

The most useful one I think is this though:


It describes the ratios of different wavelengths required to reach a good white balance. As you can see, 445nm is very efficient at shifting the color of the light; nearly twice as much 473 is needed. The problem is just that it's not very luminous, meaning that the purely blue 445 beams will appear far weaker than had they been 473. Luminance can of course be added with 532, but at the cost of saturation (and a higher "equivalent" wavelength).

There aren't many choices in power for 445 these days, right? I only know of 0.5 and 1W. Given those alternatives I'd say 0.5W is definitely the right for you.

[p1t8ull]

So .... get 445nm at say 500mw and mix with 475 or just forget the 475 (which would suit me as can make another unit that way.)
A one watt 445 is available just the mortgage isn't...

Any feedback would be appreciated.

I haven't seen too many 445nm lasers in the flesh (and not metered any of the quoted power levels of the ones I have) so this is by no means definitive... From what I have seen of 445nm I would say a ratio of 500mw/445nm with 500mw/532nm and 900mW/640nm will not quite be enough blue for beam shows but may just about be ok doing graphics.
At the last UKLEM, Martin (Pelosh) bought along a very nice compact 1w RGB from Kvant that was made up of 300mW/532nm, 300mW/640nm and 500mW/445nm. In these ratios many commented on the very nice colour balance and range of colours this thing produced in (sometimes VERY thick fog ) this was doing mainly beams and I thought the first colour to "disappear" was the blue.
I must admit that if I were in your shoes now I'd be leaning heavily towards mixing 250mW/473nm with 500mW/445nm for the benefit of both balance and palette.
That's my 2p worth anyways

[The_Doctor]

It describes the ratios of different wavelengths required to reach a good white balance. As you can see, 445nm is very efficient at shifting the color of the light; nearly twice as much 473 is needed.

Why? I've wondered about this regarding wavelengths at either end of the visible spectrum, but always assumed that advice on the 'bell curve' of sensitivity meant that white balance was always founded on perceived brightness of the individual colours chosen for an RGB mix. If this is true, for several people, it means the standard teaching is wrong. While I hoped it might be, I never held that hope seriously. I'd hoped it might be true of more extreme ends actually, so that tiny amounts of green might make awesome deep blues when mixed with 405, but never believed it could work that way because the weakness of sensitity for 405 overrides all strengths due to combination with it. And now you're saying that 445 nm CAN do exactly this, to some extent. As far as I know, there is no unusual peak sensitivity to that wavelength in the standard curve, let alone one stronger than the mid green peak, so what's happening at 445 nm? And is there one with similar effect at the red end too?

EDIT:
p1t8ull just mentioned graphics. Is that related? Is it that 445 has some useful combination of reflection AND fluorescense that makes a strong combined blue when used on a white screen? Or does it work for beam shows? If so it's extremely odd and needs investigating because most (all?) show-use fogs are not fluorescent so we can rule that out.

[mccarrot]

The most useful one I think is this though:

With this chart, did you also think about the foreward scattering effect?
the beam scattered off the smoke.

650nm and 671nm you will see better with thick smoke becaue of this effect, compared to 640nm I think the same effect will aslo apply on the blue.

This mean the above chart can be correct when shining the beam on a white surface, but can be different with a beam show.

[tocket]

The intuitive model is that if you mix equally bright R, G and B sources, you'll get white. This is usually not the case (it can probably be if you chose your wavelengths right). I know that it can be hard to accept this, because I've struggled a bit myself. My first models (before I picked up the literature) were based on such an assumption, and I ended up gravely overestimating the amount of blue and red needed to make white.

If we look at the for this topic very relevant color matching functions:

The first thing you might notice since we're discussing blue here, is the large peak at 440 nm. Note that the color matching functions are not the same as cone responsivity. It is a mathematical construction to convert between spectral power distributions and color perception. The bell shaped green curve is actually the luminosity function, i.e. luminous (bright) the different wavelengths are. It is normalized to 1 at its peak wavelength 555 nm, but if you multiply it by the luminous efficacy at this wavelength (683 lm/W) you get it in a useful unit.

Now, the role of the blue and red curve are a bit more complicated. To put it simply, if you want a large blue shift you need the ratio between the blue and (green+red) curve to be a large as possible. For the maths behind it, see:
http://en.wikipedia.org/wiki/Color_matching_function

These calculations are for reflection off a perfectly white surface (no fluorescence involved). Scattering by large particles (haze/fog) is not strongly wavelength dependent, so it should apply to that too.

[The_Doctor]

I've seen that before, but not recognised what it meant. The idea that you can get white with less blue than green is odd. Wasn't expecting that. Amazing that no-one's mentioned it before in lasers. So far as I know... I'm not good at maths but I'll try to work it out. Probably won't though, I think I might have to see it in practise to grasp it for real.