What is your color balance for a nice "white?"

[DanG]

I have read through a couple of technical discussions on the subject about what is a good white per the math (kudos to tocket for an excellent! thread) but in life and in design I prefer to fly by the seat of my pants and frankly we are selling to someone's eye ...

So I ask, what proportions do you use to achieving a pleasing white to your EYE? We are working with 640, 532 and 455. Some of our blues are actually closer to 450 and I imagine there is a lot more data for 445 so lets just use the 445 experience unless someone has 455 which would be perfect.

We need to zero in on a range to focus our R&D before we can get it on the bench and fiddle more precisely for a new product we hope to have launched by the end of the year. Thanks!

[-bart-]

Problem is, if you're in a dark room with no reference, 30% of the perceivable color-gamut could be labeled as "white". And rightfully so ! We don't use our projector to display color-photos. Don't treat a projector as if it were a reference crt.

imho:
Color balancing only makes sense if you have more than one projector.
Additionally, chroma only makes sense if your beamspecs match.

In fact beamspec matching could be more important to color perception than color-balancing.

[norty303]

I'm using roughly equal amounts of 640, 532 and 445 but it's a bit light on the red.
I would say try equal parts of 532 and 445 and 1.5 times the same amount of 640 as a good starting point.

[andy_con]

who cares about white!!

buy as much colour as you can afford then use the software to sort white out.

generally 532, 445 and 640 you use a ratio of 1:1:1 for a nice white but then when 640 and 445 are on their own they are not bright enough.

[logsquared]

I am still getting used to 445nm in my projectors. I use 658nm red so can't really share anything about 640. I have found with 445nm the mix for graphics and beams is totally different. For beams i have used 1-1-3.5. This works well, a little weak on red. Also, a little weak when using straight 445. Just a little bit of 532 added to the 445 seems to make a huge difference in perceived brightness. For graphics 2.5-1-2 seems to work ok. This would be the minimum amount of red I would consider acceptable when projection on a white screen. After adding the 445 I have spent a lot of time on the color training to get the cyan region to not look white. In all my new projectors i am going to aim for 3-1-6. This should allow for good mix on graphics and beams.

So, I guess a "nice white" depends on what the application is.

I think the truth is most people respond to brightness more than spectrum. 9 out of 10 clubs will want a 1w green over a balanced 1w RGB after seeing both side by side.

[DanG]

All good points and thanks very much for the responses.

We are looking at an application where up to seven projectors would be used side by side per area run in a daisy chain so we need to ship them balanced appropriately for that use.

I appreciate the feedback.

[MisterWilling]

Also, a little weak when using straight 445. Just a little bit of 532 added to the 445 seems to make a huge difference in perceived brightness.

Very true, when I did a graphics show for my work the 445 looked okay close up but very fuzzy from far away. Adding a bit of 532 made it look much better and it still looked like a nice blue, just not as dark.

[White-Light]

I think it all depends on how you like your colour balance.

A look at Kvant Specs and you'll see they're very heavy on the 445nm.

eg Their 2 watt Spectrum uses 1w 445 to 600mw 640 to 500 532 which is almost 2:1:1 in favour of blue.

This seems to make very strong purples and pinks but personally (and controversially) it seems to my eyes to adversely affect the lighter end of the spectrum too. Personally I prefer a projector with either a lighter blue or a heavier red balance.

My own but so far untested balance based on theory would be 500mw 457, 900 mw 640 (actually 800 but you can't get that in a module), 500mw 532.

So I'm almost 2:1:1 in favour of red.

Personally I'd use 457 or 473nm for blue anyway as I'm not a 445 fan for the reasons I mentioned above. However, now 445 have dropped in price, its very diffcult justifying the other expensive blues in a projector as when competing against other companies it puts you at a huge price disadvantage. However, if building privately and if I had the money, I'd be buying 457nm to take a look at it as I've ehard nothing but great reports both on colour, luminostiy and beam specs. I don't think I'd increase the blue even with a drop to 445.

If you're looking to produce projectors commercially, why don't you just buy some large lasers that are well over the maximum specs of the laser you're looking to produce eg 1 watt each then detune them in the software in various ratios to assess both white balance and overall colour balance. That way you can experiment with lots of different mixes until you find one that really works for you.

[DanG]

... why don't you just buy some large lasers that are well over the maximum specs of the laser you're looking to produce eg 1 watt each then detune them in the software in various ratios to assess both white balance and overall colour balance. That way you can experiment with lots of different mixes until you find one that really works for you.

That was a great response and very helpful. Thanks!

The short answer is that I don't need one... I need about five sets and buying five large RGB sets just to detune then in strange ratios - because have to compensate unusual losses - without the best possible idea of the mark to hit would probably just be wasteful. It would though make a great fire-sale when we were done with it. =)

[logsquared]

curious what 455nm diodes you are using?