CurtPalme.com Home Theater Forum

[Spanky Ham]

I was reading this article and thought it might be of interest. From reading the article, Cube Calibration eliminates some of the variables and gives more data points. I guess you would need a Lumagen or the Colorbox to be able to do this. Freaking Lumagen owners always getting value added. Has anyone tried this with their CRTs?
http://www.hometheaterhifi.com/video-calibration/video-calibration-reviews/cube-calibration/all-pages.html

[Phoenixed]

Isn't this just 3dLut calibration?

[kal]

Yup - been around for about a year or so.

You need to use something like ChromaPure advanced Auto-calibration when doing the 125 point cube calibration with the Radiance because you simply cannot do that many points by hand. It would take forever.

More info:

https://www.curtpalme.com/forum_archived/viewtopic.php@t=32073.html

Kal

[kal]

Yup - been around for about a year or so.

You need to use something like ChromaPure advanced Auto-calibration when doing the 125 point cube calibration with the Radiance because you simply cannot do that many points by hand. It would take forever.

More info:

https://www.curtpalme.com/forum_archived/viewtopic.php@t=32073.html

Kal

[CIR Engineering]

Yeah, Lumagen uses a 5x5x5 (125 point) matrix. We rolled it out at CEDIA last show.

Really, the cube has always existed, we used to only just be able to calibrate the 100% saturated points in the old days

craigr

[Spanky Ham]

Wow, where have I been?

Craig,
Have you used it before for a CRT? I know you said that autocalibrate doesn't work correctly with CRTs.

[CIR Engineering]

I wouldn't use a 125 point CMS on a CRT. The reason for this is that the phosphors natural emissions are correctly proportional without intervention. In other words, if you get the three primary colors in the correct places at 100% saturation, and your greyscale and gamma are balanced for the three tubes, it is physically impossible for the color cube to NOT be correct.

On a digital projector colors have always been problematic. When a digital system interprets an input signal, it is up to the system to decide what colors it creates from the digital signal. The digital projectors RGB color decoding is a "black box" if you will. The original video input must be interpreted by the system and then recreated by the digital projector. There are no physical barriers (as with CRT) to constrain the digital projector to accurate colors. Because of this, the design of the black box may allow for very inaccurate color reproduction. This is blatantly obvious on some projectors and less so on others. On really good example is with the Sony and Epson digitals. When these are calibrated using a traditional 6 point calibration, the resulting image is VERY under saturated looking. It would measure technically correct, but look terrible. This is because the colors that were less than 100% saturated were not being put in the correct space inside the cube (under saturated).

With analog, the signal is an analogy to the original. With digital, the original analogy is lost and is left to the encoding and then decoding by the projector. The entire system of colorimetry in video is based on the response of phosphors. Thus the digital projectors strive to reproduce the response that one would expect from a CRT. Most digitals don't come close, but with a high number of calibration points (finite elements) the digitals can be force corrected to match much more closely.

craigr

[Spanky Ham]

Craig,
You don't know what you are talking about. The guys at AVS are my gods and they say I need it.


Your explanation makes a lot of sense with regards to the difference between digital and CRT. It sounds like the digital owners really need this to get the best out of their pj. One thing I don't understand is it seems like you would need an even better meter to do cube calibration accurately. I know they said in the article they used a C6. I would guess that this meter (or its equivalent) would be about as low as you would want to go.


I truly believe that a lot of people are calibrating and believe they are achieving good results. Unfortunately, they probably have no idea what a good calibration looks like. Having seen your CIR90, I believe that was one of the most accurately calibrated pjs I have seen. If people saw that image, then they might have a reference to go on. Instead they have to try to go on faith and compare to the real world, which doesn't always work.


Now, it has been about six months. How are your two new children working out? You said in another thread you really liked the Klein, but it still need to be offset with the PR. You had just purchased the Jeti. Are you using the Jeti instead of the PR? Is it better or about the same? Have the G90s gone from CIR90s to CIR+90s?

Inquiring minds want to know. Don't be shy. It is my thread, so pimp away. You, Curt, MP, Mac and Scott are the most knowledgeable CRT guys on the forum. I haven't seen Scott post in awhile, so I am not sure if VDC packed him in the last 9500 and shipped him out or not. The CRT guys are dwindling and might be down another expert.

[the big E]