638nm vs 637nm (single mode vs multimode)

[drm916]

it can't just be me but my problem is red always looks wimpy... you have these awesome blue and green beams that turn the entire room that color... and then the red beams are these wimpy laser-pointer looking things that make the room black... how much power would it take to turn the room red?!

I agree. Forget about white balance.. I want booming big red. I am guessing you need like 4 times the amount of green in the projector, to make it look as visible. I love it when I see a show with a shit ton of red.

[catalanjo]

To get overall impression of lots of RED...best is to use both reds = 650nm AND 638nm (leaving the 650 big and FAT) for beams and aerials and just use the 638 on it's own when doing graphics.
If you leave both on for graphics the will be "smudgy" and your white will look PINK!

I try to use at least same power as dark blue 445nm between both reds .......and that works!
Cheers
PS. The violets at high power are mind blowing ! (a bit like ARGON violet !)

[flecom]

ya I have 642/650 already (1.2W 642 2W 650) and it still sucks

[dkumpula]

I expect it's all down to perspective. Also the fact that doubling of power is nowhere near double the brightness

From what I've read while reading lumen studies written with video projectors in mind, human perceived brightness is roughly a logarithmic function of increased lumens to the tune of doubling the lumens results in a 50% increase in perceived brightness.

Now combine this with photopic vision studies (where perceived brightness of different colors is measured by a person with "normal vision") and the difference in sensitivity to different colors (both for rods and cones) and I expect the conversation to get muddled a bit. Further, enter the laser world where varying divergence, initial beam size, distance from the beam, varying sensitivity to certain wavelengths in both bright and dark adapted environments (including on a person-by-person basis), etc, etc. . . oh my. It seems like personal evaluation may be the easiest way to compare two sources for 'apparent brightness'.

-David

[catalanjo]

No 638 ?
Cheers

[flecom]

No 638 ?
Cheers

soon hopefully if I can get enough of it... my big projector isn't for graphics so I am not concerned about white balance or beam quality that much... I have nice stuff for graphics already

[planters]

I like catalango's approach. Good quality red remains limited, but if you built a specialized projector that only fired red and used multimode diodes at 638 and 650, cooled and run hard this could still be very compact. Without blue and green and the drivers and the beam paths the reds would have room to spreed out. For beams, the scanner can be big and slow and so this further allows you to increase the diode count. If you cool these 30-40C the apparent brightness of both wavelengths doubles as well.

My largest projector uses six, cooled, P73's and puts out a powerful red beam. To truly make the room look red, I think 3x that power would do it. Keep in mind that red scatters less in haze and that combined with the lower visual sensitivity really hits red hard compared with green.

[catalanjo]

............six, cooled, P73's and puts out a powerful red beam. To truly make the room look red, I think 3x that power would do it..........

I wont wun of dem fings! ..................

Cheers

[kecked]

get some of those 5W C mount diodes that where around a while back. 4 of them stacked would be incredible. Of course the beam after a telescope would be 2" in diameter once you correct the divergence.

[carlos3621]

it can't just be me but my problem is red always looks wimpy... you have these awesome blue and green beams that turn the entire room that color... and then the red beams are these wimpy laser-pointer looking things that make the room black... how much power would it take to turn the room red?!

I can turn a dark room red with 3 watts of 637 single mode,
Pretty happy with 3 watts of red, it is just about the minimum amount i would ever spec. Any new projector purchase.