Beyond Color Settings

[planters]

Just a quick note. For anyone like myself that originally set up an RGB projector with the 3 color LINEAR choice assuming that the linear driver needed a linear input, go to the P. tutorial #2 and reset to the LOGRITHMIC control and adjust the thresholds as described. The improvement in range of color and saturation is ...well stunning.

[norty303]

Got a link to the tutorial please Mr Planters?

[White-Light]

Just a word of warning here.

I too found this out and thought I'd found the answer to my colour balance issues.

However, try applying a BAM.

If your lasers are linear and you apply log, you'll find they extinguish at very high power levels. eg 70 or even 80% power could be totally off. This could then leave you with probems where you need BAM @ levels below these cut off points.

You need to establish from the modulation characteristics whether they're linear or log and then if necessary rebalance your colours using another method, in my case I use the adjustment screws on the projector. I'd imagine you could probably fine balance then in the software although personally I haven't done this on mine yet as I've got a good colour balance the other way.

If your lasers are log, then I imagine no problem. If they're linear and you set log then....

[planters]

However, try applying a BAM.

I confess ignorance here. BAM? For what it is worth don't the test patterns project at 100% max brightness? If not, they are damn bright and flat white.

http://www.youtube.com/watch?v=BOX0U0b0qSE

Above is the link for what it's worth.

[badger1666]

Beam attenuation map
Excuse spelling

[norty303]

You shouldn't be assuming a BAM will give X% power reduction anyway, as many lasers are not linear in their output.
You should measure at the required output and see whatever that is in percentage terms.

Although some finer granularity than 10% on the BAM settings would be desirable.

[White-Light]

You shouldn't be assuming a BAM will give X% power reduction anyway, as many lasers are not linear in their output.
You should measure at the required output and see whatever that is in percentage terms.

Although some finer granularity than 10% on the BAM settings would be desirable.

I wasn't suggesting you could take eg a 20% BAM on a 1 watt laser and assume its 800mw.

What I was pointing out was that if you set linear lasers to log, you may find that you cannot in my experience apply a BAM of more than 20% or so without having some lasers extinguish or appear almost out very quickly and without warning leaving no room for setting many power levels that would fall between the changes found in the set increments of the BAM adjustment, given that the entire modulation appears to fall within such a small BAM area (or more technically voltage adjustment). This causes problems for situation where you might want the power equivolent of a 40,50,60 or 70% BAM but find this unavailable because of the steep drop off at such a small voltage adjustment. IF you look at a typical log response curve, although its steeper than a linear curve, I still wouldn't have expected such a tight cut off but rather a linearish curve at 1st then a steep drop off towards the end when low voltage levels / BAM settings are set. Instead what appears to happen is if you set apparently linear lasers to log is you get a steep drop off very close to the 100% end leaving little room for adjustment.

What I also found was that whilst setting log solved some colour problems with eg some suble colours eg taupe, it also threw some others out in return on closer investigation, so what at 1st appeared like a fix was in fact a simply shifting the colour balance problem onto other cues / colours.

The typical most problematic cues for me in the QS workspace are:




These are the ones (Sheets 02 & 05) I find have a tendacy to display as white in whole or in part if your colours are unbalanced by a lot or as incorrect shades if the balance is more subtely out.

Setting log for me cleared these problems up but then threw other bolder colours out elsewhere most notably orange.

For me in my projector, turning the red down (which was the last thing I would have expected being overblued), balanced these colours and corrected all of the other colours as well whilst a linear setting maintained the modulation characteristics and allowed the application of quite low BAM settings.

How you're supposed to tell if your lasers are log or linear, I don't know. I've just applied the presumption to mine that if they won't modulate beyond 20-30% reduction then they're linear given that log affects the modulation and most lasers are noted to be BAM'able to quite low levels.

[norty303]

What would be nice is to be able to set log or linear for each colour channel, as most people are likely to have a mixture of diode and dpss in their projectors.

[White-Light]

What would be nice is to be able to set log or linear for each colour channel, as most people are likely to have a mixture of diode and dpss in their projectors.

Suggest it!!!

It would also be nice if Pangolin or someone could produce a definitive guide on how to analyse your lasers to tell if they're linear or log modulated, especially if it were possible to produce a method that didn't involve extra test equipment.

[norty303]

It's easy if you have a power meter and a variable voltage source for modulation.
Apply 0 to 5v in 0.5v increments and record the measured power for each one. You'll soon see if the response is linear or not.