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cmjohnson
Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s
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Link Posted: Sat Apr 01, 2017 5:12 am Post subject: Wanted: Good luminance (light) meter |
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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.
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kal Forum Administrator
Joined: 06 Mar 2006 Posts: 17860 Location: Ottawa, Canada
TV/Projector: JVC DLA-NZ7
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kal Forum Administrator
Joined: 06 Mar 2006 Posts: 17860 Location: Ottawa, Canada
TV/Projector: JVC DLA-NZ7
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cmjohnson
Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s
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Link Posted: Sat Apr 01, 2017 2:28 pm Post subject: |
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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.
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kal Forum Administrator
Joined: 06 Mar 2006 Posts: 17860 Location: Ottawa, Canada
TV/Projector: JVC DLA-NZ7
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Link Posted: Sat Apr 01, 2017 2:40 pm Post subject: |
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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!
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
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Last edited by kal on Sun Apr 02, 2017 1:23 pm; edited 1 time in total
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cmjohnson
Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s
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Link Posted: Sat Apr 01, 2017 9:07 pm Post subject: |
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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.
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kal Forum Administrator
Joined: 06 Mar 2006 Posts: 17860 Location: Ottawa, Canada
TV/Projector: JVC DLA-NZ7
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Link Posted: Sun Apr 02, 2017 1:28 pm Post subject: |
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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 wrote: | ...something that's pro grade but not too expensive... |
If pro grade is what you need (highly doubtful) they're much cheaper than they used to be back in the days of the LS-100 when good meters were about $15K and up. Pro-grade today starts at about $5K which is a massive drop in price. The CR-100 I mentioned above is where pro grade starts today: http://www.curtpalme.com/ChromaPure_CR100.shtm
There's no such thing as a pro grade meter that "isn't too expensive". The only way to get something like this would be to buy a used one that someone is selling for a fraction of what it's actually worth.
One thing (among others) that made the Minolta series so expensive is that they're 100% standalone. You're paying a lot of money to have a unit that does all the calculations/processing onboard. If you have a laptop/PC, use a tethered meter instead and save yourself $10K+.
But again, I highly doubt you need something pro grade. None of the requirements you've stated indicated you'd need pro grade. The few hundred dollar Display 3 PRO would most likely suite your needs: http://www.curtpalme.com/ChromaPure_EyeOneDisplay3.shtm
If you provide accuracy requirements we can help further.
Kal
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cmjohnson
Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s
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Link Posted: Sun Apr 02, 2017 1:47 pm Post subject: |
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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.
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kal Forum Administrator
Joined: 06 Mar 2006 Posts: 17860 Location: Ottawa, Canada
TV/Projector: JVC DLA-NZ7
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Link Posted: Sun Apr 02, 2017 2:57 pm Post subject: |
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cmjohnson wrote: | Well, I have a taste for pro grade equipment even if I don't actually NEED it. |
Nothing wrong with that. I tend to buy pro grade when I can too as I like the build quality. Not with meters though as it's 10x the price however. That to me doesn't make sense for how I want to use it. If you do end up buying a really old pro-grade meter (like an LS-100) make sure to budget in a professional recalibration too. There's no point in using a ~20 year old meter if it's drifted so far as to be less accurate than a $100 one.
Quote: | 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. |
The reverse is true too: If you use a 100% standalone meter (no data connection at all) then you have no way of easily doing data capture and creating reports/graphs/etc. You have to manually enter all the data into whatever tool you're using so it actually becomes much more difficult to use. Pros don't tend to use their reference meters for readings for this reason (and others). They use them to calibrate their field meter.
Quote: | 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... 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. |
Any meter will do this, even a $100 Spyder. If a meter can't meet these requirements there would no point in it existing.
And again, you haven't given any indication on what you mean by 'accurate'. You need to read/understand this article to which I posted a link earlier: Colour Science: About Meter Accuracy. Link: http://www.curtpalme.com/forum/viewtopic.php?t=22015
Quote: | What I don't know is how good most meters are down in the dark grey region. |
Again, give my "Which meter is right for me?" FAQ a read: http://www.curtpalme.com/forum/viewtopic.php?t=11436
It covers this.
Kal
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cmjohnson
Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s
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Link Posted: Sun Apr 02, 2017 4:27 pm Post subject: |
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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.
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kal Forum Administrator
Joined: 06 Mar 2006 Posts: 17860 Location: Ottawa, Canada
TV/Projector: JVC DLA-NZ7
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