Do Calibration Tables Really Work for Tri-Stim Devices? (Updated)

Addendum – I had a chance to play with a one of the new Samsung E8000 series LED sets.  I first placed the C6 up to the set and calibrated the display with that device and the tables.  The C6 is in contact with the face of the screen.  Next up I took some readings from the Jeti to see how well the C6 did.  The Jeti was tripod mounted and about 22 inches back from the screen.  The laser pointer on the jeti showed it was looking at a similar surface area of the screen.  The following then is a series of images starting with the C6 tables version and then eight readings of the same tv, but spaced about 9 inches further away each time.  So with the first reading being 22 inches, the second is 31 inches … then 40, 49, 58, 67, 76, 85.  I’ve known the end result would be like this for years as my old CS200 behaved similarly, but I never felt the need to document that behavior.  It pretty much dispels the excuse that somehow the Jeti and the C6 were not looking at the same spot on the TV so of course the results are different. Uh … no.  It doesn’t matter and it shouldn’t matter if you actually take a moment to think about it.

 

First printed Nov. 11, 2011.

Revised Dec 30, 2011. Added Sony images.

Revised Jan 19, 2012. Added Samsung images and addendum.

Revised Jan 25, 2012.  Added addendum on X-Rite i1 Pro 2.

Revised April 17,2012.  Added addendum on varying distance for Jeti.

Michael Chen

Michael Chen is the only THX Video Systems Instructor in Canada, and beyond these borders, is one of just two THX Video Instructors in the entire world.  He has actively consulted with Spectracal and ChromaPure and has created numerous education videos on the calibration process with still more to come.  His Video Calibration Training Series has quickly become the most comprehensive and simple to understand learning tool on the market today.  He has also taught classes for both the ISF and Spectracal as well and is now spearheading his all new TLVEXP calibration training program. Let Michael teach you Video Calibration and add that additional income stream to your installation and integration business

25 Comments

  • Can I get a datestamp on this article?

    It’s a very very good article, by the way. Albeit depressing for the owners of colorimeters. I suppose the best would be to own BOTH the iPro and a colorimeter so you could get the speed and accuracy of both on a given display.

  • Excellent article. For some enthusiasts economic situations could exist where the purchasing of a $1000 spectrometer is out of the question or to even borrow or rent one again is out of the question. Even if one does have such a equipment; how accurate is the reference unit?

    • A man with two watches never knows what time it is.

      I’m not telling everyone to rush out and buy a spectro. The i1 pro can usually be found for under $1000 and the Color Munki Spectro is usually well under $500. The article simply presents the argument that one should not put blind trust in calibration tables. They are not always right … or in the case demonstrated in the article … one was close and three were much further off. The sets were not cherry picked … they were simply the 4 sets I decided to put the meter to.

      There is a way to make the tables better. They just are not there yet, but hopefully adjustments will be made and the accuracy will improve.

      The thing about the spectros as mentioned in the article is that their behavior does not change depending on the type of TV technology you ask it to read. They are consistent on LCD … Plasma … LCD/LED … DLP … OLED … LCOS … it is not a Wheel of Fortune where you cross your fingers not knowing what the meter results will look like.

      I’ve added a shot of the same panasonic LCD set, but using my aging i1 Beamer / pro. This is the verification I expect when I put a second meter up to a TV. I don’t expect it to be identical, but I do expect it to be reasonably close … and it is. Therefore I have confidence in the i1 and my Jeti.

      Regards

      • Can you use the i1Pro to measure the LG LED-LCD? Since the C6 was way off on that TV, it would be the best example to show how much more accurate the i1Pro can be.

        • I will work on that … easier said than done … a lot of sun light in that room. 🙂

          • Thanks for the update. This really makes the case for owning an affordable spectrometer for DIY’ers like myself. Colorimeters are not bad devices, they just need to be paired with a spectrometer for absolute accuracy.

            Also, it seems your i1Pro from 2002 has maintained its accuracy very well over a decade. Another reason to own a spectrometer in my opinion, since it stays accurate and you don’t need to send in your colorimeter for re-calibration as long as you use the spectrometer to profile it each calibration session on each display.

  • Michael,

    The i1 seems to be reading luminance a lot lower (for both the panasonic and the lg display). I am not sure if this is measurement issue or just a case of reporting on the charts as the luminance seems to be lower by about 30% for all values.

    • Good observation. I will take a look at the way the i1 pro was mounted for these readings which was on a tripod about four inches from the screen. Will see what the difference is with direct contact. In a real world application, it might mean that light output gets set to a higher level as a result, not that big of a deal. Is that necessarily a bad thing? From a contrast setting perspective, the eye fatigue consideration trumps exact light settings anyway. A mental correction factor could always be added too … Take reading and multiply by 1.5

      Just don’t be using the i1 pro for studio reference set up work … which it isn’t supposed to be for anyway. 🙂

      • I did a verification with the i1 pro … and it reads the same light output when in contact with the screen or when it is 4 inches from the screen on the tripod.

        Good idea to stick with the multiplication factor when trying to figure out exact readings.

        • Would a new i1 pro still read luminance a lot lower than the C6?

          • I had Ray take a few readings with his C6 and his i1 Pro … a real one. The luminance readings were identical to the c6. Seems some progress was made over the 8 years to when he got his unit. I get to use the 1.5X multiplier … he does not need to.

          • Based on this data, it appears tables for LED-LCD’s have issues but for CCFL-LCD’s not necessarily so. Do you have access to any other CCFL-LCD’s to see if this theory could be true? Is CCFL backlighting more consistent among LCD displays than LED backlighting?

          • Did two other LCD CCFL displays in my home … a 46″ Sony unit from 2007 time frame and a 23″ Samsung computer monitor (2009). Delta E average error was 1.0 for the Sony and 0.6 for the Samsung. Largest single deviation was about 1.5. There is consistency here and with the Panasonic, the tables can get within a range of 2.0 or better … consistently.

          • How do the tables hold up to plasma displays?

          • Answer … I don’t know. I will have a chance to play with a bunch of plasma sets in the coming weeks so will see what happens.

  • Looking at the latest addendum, it seems that FOV does not alter the results from the Jeti at all. Also, the calibration tables seem to have worked quite well on this particular display.

    Was the new wide gamut white LED table used on the C6 for this test? SpectraCal claims the new table was added in response to the discrepancies noted in earlier tests within this article on LED-LCDs. I’m assuming the standard white LED table was used in the past for the LED-LCDs tested in this article.

    • Latest version of Calman so latest tables. I try both LED settings and pick the one that is closest to the JEti. Problem is … I can confirm this with my reference tool. Others not as fortunate. And how exactly do you know if you should be choosing a white LED type of a color LED type? The User manual does not exactly say stuff like that. 🙂

      • I guess sites like Panellook and forums like AVS can help you find out exactly what the backlight type is.

        I thought all current LED-LCDs use white LEDs and that RGB LEDs were a thing of the past. Also, standard gamut white LED sets have smaller than Rec. 709 gamuts while wide gamut LED sets have standard sized gamuts like those tested in this article. That’s what I read in the SpectraCal forum.

  • I have a question about the i1 pro spectro to which I cannot seem to get an answer to. At lower light levels, say below 30% white, it is known the i1 spectro takes a lot more time to do a reading. But is it still accurate? I’ve heard people say it loses a lot of accuracy at lower levels as well. But when I read 10% and 20% on my panny VT50 plasma, I do get the same reading consistantly. Now I do not know if those readings are accurate, but I would expect that if they were inaccurate, the reading would turn out differently with each taken reading…

    • The i1 Pro bottom end issues are not so much a 10-20% issue as opposed to a light output issue. 10% on a typical projector in a dark room is not the same as 10% on the VT50 plasma tv. If the readings at 20% and 10% appear linear and relatively in line with 30% and everything else, you are good. The i1 pro is just fine for your application.

      On the projectors, at the 10% level … and sometimes the 20% … the readings are simply wildly inconsistent.

      Remember to always use your eyeballs to double check the probe results. On a projector, the i1 pro might sometimes return a reading that says the pattern is too green … but visual inspection says no.

      For a double check on the dark end on your plasma … do a dark reading and then immediately take a few readings of those dark patterns. You get the best results than. We do that on the projectors too especially on the dark end. We do a dark reading every few minutes so that we can be sure of the results or when to disregard them.

  • I would like to ask you, how do I best take a dark reading? With the white tile ( I have the i1 2 spectro), or is a black bag over the device enough? Also, in chromapure, can you do in-between dark reading? I only manage to do so by disconnecting the device (not fysically, but in the programm) and then selecting it again, so it automatically asks for a dark reading.

    Thanks for taking the time to answer my questions 🙂

  • There should be an option under the tools menu at the top for taking a dark reading.

    I’ve done things like putting the unit up to the clothing or on my lap for dark readings. It is all the same. A dark surface. Even my hand when in dark rooms.

    regards

    • Regarding taking dark readings when using the i1pro in contact mode, is there any easy way to do this without having to take the meter off-screen and then be forced to re-position it?

      • A few mm won’t make a difference and I can just use a finger to block the light. It it is off by a few mm and the readings are that different, then you have bigger problems. 🙂

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