CurtPalme.com Home Theater Forum

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I'm looking for a good luminance meter for projector calibration. Something comparable to a Minolta LS-100,
something that's pro grade but not too expensive.

Let me know what you have and also feel free to make recommendations to me even if you don't have one to offer to me.

**kal** · Posted: Sat Apr 01, 2017 2:13 pm Post subject:

AEMC CA813 illuminance meter comes highly recommended by those in the calibration field and they're inexpensive too (under $200) - click on pic for details:

Link: http://amzn.to/2nI1WyI

Kal

**kal** · Posted: Sat Apr 01, 2017 2:16 pm Post subject:

For what it's worth, I've been use this even cheaper one myself for years and am happy with it as I'm not a 'pro calibrator' (click on pic for details):

Link: http://amzn.to/2oKNWDu

Kal

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

More information on the application: Precision adjustment of color balance and intensity at all contrast modulation zones, with CRT projectors such as the Marquee and the G90.

I want accurate calibration of color and intensity across the entire grey scale at all adjustable points on the screen.

Using a Minolta LS-100 kind of spoiled me. I'd love to find a good used one for a bit less than they usually sell for on ebay.

But as long as I get accurate results and it works for my application, that will be sufficient. Spending less money is of course a bonus.

**kal** · Posted: Sat Apr 01, 2017 2:40 pm Post subject:

If you want to calibrate colour then you need more than an illuminance meter. You need a colorimeter or a spectro.

The Display 3 PRO is very good for the low cost: http://www.curtpalme.com/ChromaPure_EyeOneDisplay3.shtm
If you're looking for "pro" grade colorimeter, the CR-100 is a good bet: http://www.curtpalme.com/ChromaPure_CR100.shtm

You'll need to think and be specific about what you mean by "accurate" as that's not a statement that can be quantified. That's like asking on a car forum for recommendations on a car that is "fast". Depending on your needs, a $20K Honda Civic may meet your needs, or maybe you do actually need a $2M Bugatti. Don't know! Wink

Finding a good old reference grade meter that used to cost $15-20K for cheap usually means it's not worth much anymore because the calibration has drifted considerably. You'll spend more getting it re-cal'ed than what you pay for the meter. (Assuming recalibration is even possible / still available for the model in question).

Give my "Which meter is right for me?" FAQ a read: http://www.curtpalme.com/forum/viewtopic.php?t=11436

Also read this: Colour Science: About Meter Accuracy. Link: http://www.curtpalme.com/forum/viewtopic.php?t=22015

As you go up in cost there's most definitely a law of diminishing returns in play here. If you're needing to play in the NIST certified type accuracy levels arena then be prepared to pay yearly to keep things within that original accuracy tolerance. Most people (even most pros) do not need this.

Kal

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

The LS-100 can certainly be used for color calibration. 73-20-7 (G, R, B) are the light ratios for calibrating a 6500K white point, at any given IRE level. So if you are shooting for 10 foot-lamberts at 100 IRE, green is set to 7.3, red to 2.0, blue to 0.7.

As long as the RGB illuminance responses are calibrated to equal energy sensitivity, this kind of meter is certainly useful for color calibration.

In the past several weeks I've calibrated about 30 freshly retubed Marquees. While I would not call myself an expert at it yet, I can say that I learned a lot about calibration based on a light meter like the LS-100.

**kal** · Posted: Sun Apr 02, 2017 1:28 pm Post subject:

An LS-100 can certainly be used. I misunderstood originally you were only interested in measuring luminance, hence my original recommendations which I then clarified.

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Well, I have a taste for pro grade equipment even if I don't actually NEED it.

Why else would I use QuantumData pattern generators? Because they're awesome and I got one at a righteous price,
and I LIKE standalone equipment. There are situations where dragging out a PC to do a job that can be done by a self-contained
standalone device is not the optimal answer for me.

As for my requirement, I want a meter that has the sensitivity and accuracy required for me to be able to measure color balance at every IRE value from 5 to 100 with a reference brightness that may be anywhere from 3 to 11 foot-lamberts, or more, as many digital projectors can easily achieve....well, I don't know how many foot-lamberts but I know it could be quite a lot! And it has to be able to do this accurately for RGB regardless of color space being used.

I want that grey scale measured and calibrated across its full range. No visible push anywhere along the whole IRE range, understanding that gamma adjustment is going to be part and parcel of the calibration.

What I don't know is how good most meters are down in the dark grey region. And I don't know what the relevant specification would be as of yet. A meter that isn't delivering anything resembling accurate results below 3 foot-lamberts would be worthless to me as it wouldn't be usable to set up proper color tracking on the dark end of the grey scale.

**kal** · Posted: Sun Apr 02, 2017 2:57 pm Post subject:

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I will define "accurate" as "A discriminating person with perfect color acuity will not see any visible push toward any color in the greyscale of the 6500K calibrated projector". And accurate enough for a blend, stack, or tiled installation with no color imbalances apparent to the same person as described above.

Not looking for laboratory grade precision, just good enough for a really picky viewer.

Because I AM that really picky viewer. If I see a color push, it bugs me. If I see uneven screen brightness, it bugs me. I do use the contrast modulation option. But, lacking my own meter, my method of setting contrast modulation is to take the full white (single color, actually) field contrast down to "barely see it" and adjust until all zones are just as barely visible as the center. I have found that generally this gets me really close to the goal. When I had the opportunity to use an LS-100 light meter, and tried what I just described, I found that the results I got were really quite close to the goal of even brightness across the screen. Not perfect, to be sure, but closer than I might have guessed.

**kal** · Posted: Sun Apr 02, 2017 4:38 pm Post subject: