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Which Colorimeter to choose? (1 Viewer)

RWEast

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I've recently set up a home theater system, BenQ W5000, GrandView 106" tabbed screen, Samsung Blu-Ray player. In working with this system and a few other monitors in the house, I've come to the conclusion, calibrating them would be a good idea. The color difference between the various displays is very apparent.
So, to do this, I've been doing some research, and not surprisingly, am now more perplexed then before I started. There are many many different colorimeters available and as you would expect, there are a wide range of prices. Which are accurate and a good bang for the buck? Has anyone used Pantone's Huey Pro?
 

Leo Kerr

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A problem with a lot of those things like the Pantone Huey, or the i1 (which we have for our PCs) is that they're for PCs. Maybe macs, but definitely for PCs.

They generally create a loop: their software, to create an ICF profile for your operating system, to your monitor, to the sensor on the screen, back to the software.

The difficulty is, you're not running your BluRay discs through your PC; you're running them direct. And therefore, rather than the automatic "circle of life" from a lot of those things like the Pantone devices, you need.. a different sort of animal all together.

You need an animal that has its own calibrated internal references and a read-out. You then put a "known source" into the system, wash it through the projector, and then onto your screen, where you have your sensor hanging. It then compares against its internal reference, and then says, "Too blue!" You diddle the blue knob, and then it says "too magenta!" and then you try and remember your art classes to find out how you get magenta out of red/green/blue. (red+blue, by the by. Or "plus green" if you have a green knob.)

There are several difficulties with these.

1. They tend to be more expensive. The last one I looked at was in the neighborhood of $5000.

2. They often don't "close the loop." Many of them hang on the screen, looking at the projector, which does nothing for you if your screen isn't white or neutral. They're fine for CRT/plasma/rear projectors, but not, in general, for front projectors.

For example, though, the Sencore OTC1000 colorimeter for projectors is about $7000. The Sencore CP6000 doesn't include "screen color," as you'd hang it in front of the screen facing the projector, only costs about $4000.

Leo
 

RWEast

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Thanks for the response Leo.

With your indulgence, let's explore this a bit further.

If we were to use one of these display calibration devices (Mac or PC), a set of test patterns on a calibration DVD/BluRay, color calibration charts, color analysis software like HCFR or Claman, industry standard color xyY definitions, and some time and patience, an accurate calibration of the projector should be possible. At least to some of the industry standards. Is that a fair assumption?

As you say, this is not a closed loop setup. It relies on pre-published color charts and source material, known color standards and pre-calibrated sensing devices. The up side to an open loop systems is it really is a comparison of a 'Function Generator' to known published standards, and as such adjusts the output of the entire system accordingly. If everything worked correctly, it would compensate for any luminance or color shifts caused by any one of the components.

So, if I understand this correctly, there are two issues in the projector calibration.

First, is the screen neutral? If we believe the marketing material and published specs, then yes. I'm not that gullible, but without expensive sensing devices to prove of disprove the numbers (or testing by an interdependent lab), there are not a lot of options here. Let's make the leap of faith and assume it is neutral...for now.

Second are these display calibration devices sensitive enough to work with the reflected light from the screen? If so, then the gain and response curve of the screen will be taken into account during calibration. If not, then the calibration would have to be done using the direct light from the projector and the screen's impact ignored.

All this brings me back to the Colorimeter itself. I realize the value of the calibration is based in no small part on the accuracy of the sensing equipment and the way in which it is used. But, what I don't feel comfortable with is comparing the different devices themselves. Which one is more accurate, how much of a difference is there, and how big an impact will it have on the overall results? Then there is the 'always present' money equation to deal with. How much will it cost and would it be more cost effective (but much less fun) to call in someone to calibrate the set-up?

Reg
 

Michael TLV

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Greetings

Best bang for the enthusiast here is likely the i1pro device that sells in the range of $700. It is a spectrometer ... and will work on all the technologies you have. You need software to run it too though...

regards
 

Leo Kerr

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Michael,

Out of curiosity, do the ISF people like yourself use things like the Sencore boxes? I know I got to play with one some years ago (something like the CP5000 or something like that. Plugged into the USB port, and gave great measurements of uncertain accuracy... never had any chance to compare it against anything "known," although it did say that the incandescent lights were pretty close to 3000K, which was reasonable for slightly dimmed incandescents..

Anyway..

Reg,

I may not have been clear, or I may not be understanding your question. The science of calibration is, in my understanding and gross simplification, the art of documented comparisons. Be it a platinum/iridum "kilogram" sitting in a bell-jar in Paris by which all scales are supposed to trace back to, or the particular shade of blue defined by the NTSC or HDTV specs as "blue" or "gray." Or even "white." Even the "closed loop" things from Pantone/Gratag-Macbeth are doing a comparison. To something. We may not know what, but in their little minds, they have some standards that they think are accurate, and lather-rinse-repeat until their sensor reports back the same thing (or close to it) of their standard.

If you took a great signal generator and plugged it into your projector, and had the most fancy analyzer, and tuned the system to reflect perfection, you might find that your DVD player, or anything else.. isn't, which I suspect would be a good reason for using, say, a calibration DVD or BluRay, 'cause those discs are going through your source electronics, their decoders, possibly their analog circuits, et cetera. The big difference I see in my "closed" versus "open" loops is that in most PC situations, the source is also the analyzer, while in the home theater, we are trusting that who-evers calibration source and colorimeter are accurate, and that, ideally, we'd be using our players as the source, and that Joe Kane didn't mess up on encoding that test disc (or AVIA, or whoever else.)

When it comes to projector calibration, and "tuning" the screen, well, if you get a "named" screen, it'll have some sort of guarantees. If you buy some Behr White and paint a wall, well, you have something. If you're like me and used some gray cotton from the local sewing store, you have something entirely different. And yes, at least in the case of the Sencore OTC1000, it claims to be sensitive enough to use with projectors, and it uses, in essence, a telescope to look only at a portion of the screen from up to 60 feet away, if I remember rightly.

As for the tricky question of, which one is more accurate, repeatable, precise, and all of that, well, that gets really messy. To what? Here, you need to start checking calibration dates, seals, certifications, comparisons and calibrations to what? Whose standards? How long does it need before its calibrations/certifications need to be/should be renewed?

The world of measurement is... not as clean as we would like to think it is.

Leo
 

Michael TLV

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Greetings Leo,

Actually Sencore does the hard press to sell aspiring calibrators their gear. If one took a survey of all the calibrators out there ... practicing or not ... it is a good bet that many many many have been using the Sencore equipment.

Students attending ISF classes are generally only exposed to that brand of equipment before they figure out what all the options are. So most end up signing on the dotted line through ISF.

these days the CP5000 gear is not considered to be suitable for most of the digital displays out there.

Oh yes, the OTC and the 1ipro are both pointed at the screen to take calibration measurements. Nothing is pointed at the projector these days. We need to account for what the screen does to the image. Nothing is quite neutral.

Regards
 

RWEast

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Greetings,

So, lets trip down the i1 path for a bit. I have seen no less than 3 different manufacturers that have an i1 colorimeter and each with different models. (X-Rite, Pantone, Gretag Macbeth) I'm supposing 'i1' could be a generic term like a screwdriver, or a product/company that has been bought by a number of different businesses during the merger crazy years, or, could they all different divisions of the same company?
I guess what it really comes down to is what should I be looking for, before plunking down my hard earned, on a colorimeter that I could use to calibrate not only a projector/screen combo, but also a plasma screen as well as CRT & LCD monitors? Is there a secret decoder ring to use on the specs that would make them meaningful when comparing devices?
As for performing the calibration itself, I suppose as all of these devices have one or more DVI, HDMI or VGA (AKA 15 D-Sub) inputs it could all be done PC based. But, I would rather do this utilizing the device that would be used as the primary video source. By that I mean the BluRay for some devices and the PC for the monitors.
Leo, I agree the world of measurement is not as cut and dry as we would like to think it is, not to mention how messy it can get when we factor in the wide world of standards. I personally subscribe to the belief ..if the measurement is what you expected, you're probably using the wrong source. Consequently, I'm not looking for an absolute, precise, calibration. But, I do need to set up a few devices and I want to make the playing field as level as possible. I need to get them set-up to work within the nominal operating envelope for each device. I am fully aware that will mean compromises, and therefor calibrations.
Maybe then, the best thing to ask is: what would you recommendation as a set-up process. I feel a re-calibration is needed because most manufacturers set up their displays for that POP & WOW effect. To calibrate effectively and to be able to repeat the process on different devices, what would you suggest?

Reg
 

Leo Kerr

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I do like the
comment...

Yes, a lot of stuff, particularly the plasmas and LCDs seem to be set like the CRT units of old -- really blue, and flaming hot -- and calibration of some sort was absolutely required. Even if it was just pop up the color bars from AVS or AVIA and do the blue-filter gig and the PLUGE gig.

Personally, I can't attest to the importance of true gray-scale calibration, because I've never had it done. I know it is said to be important, but again, I've not knowingly had the chance to see before-and-after. Obviously, if you can see that it goes red in the shadows, there's something really wrong. On the other hand, if the gray-scale is uniform at 6000K instead of the 6500K, how important is that? To me, I suspect we'd be better off with a stable 6000K (say, +/-100K, for example,) than an unstable 6500K (+/-500K.)

But to me, the absolute minimum is to do the best you can with the consumer-available controls. Unfortunately, I've never had the option to go beyond that, beyond what I can do with my computer loop (the Pantone/Graytag i1 not-pro.)

As an aside, doing a quick search last night, I saw a reference somewhere that implied that X-Rite, Pantone, and Graytag/Macbeth are all, in fact, the same company. Don't remember where, though.

On the power of company names, I'll add another point, Michael: Sencore used to be a player in the broadcast world, with some industrial strength players and signal generators. While that might be an entirely different division, it does provide a little.. boost to their reputation in some circles, even if it's entirely unearned and invalid, of course.

Leo
 

Michael TLV

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Leo, it was one of the things that Gregg and I wanted to make sure did not happen when we helped to develop the THX Video Calibration program.

We wanted to ensure that all the manufacturers that had gear to sell that wanted to play ... would be allowed to play in the sandbox ... so long as the test equipment was evaluated to be satisfactory for the goals of the program.

That's why students get to use photo research stuff, minolta stuff, datacolor stuff, the OTC1000, and other devices in class as well as different software packages. As long as the software does not slow down the overall class, we let students bring in whatever they might already have as well to use.

This ensures that the playing field is more level and that students are exposed to many more options before they buy equipment. We did not want to hit the students when they were most vulnerable.



Regards
 

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