CurtPalme.com Home Theater Forum

Zebu Fellenz · Joined: 21 Dec 2006 Posts: 2567

Simple question, what do you do and what do you use.

I would like to get some sort of a color calibrator to use with my G70 but I really have no idea what I'm looking for. Right now everything is done by eye but I'm sure it could be much better.

My only source right now is my HTPC with Blu-ray and HD-DVD. I have the AVIA disc on SD-DVD but will pick it up on HD as well.

I'm looking for something cheap (less than $100) that will do a decent job, I know many people use the spyder sensor and I have heard that it works ok and can be modified to work better in lower IRE.

I am really clueless when it comes to all of this but I have been reading and trying to make sense of it all and hope to have something by the middle of summer at the latest.

Any Advice, Smile

Erik

MikeEby · Joined: 24 Jun 2007 Posts: 5238 Location: Osceola, Indiana

Kal is working on a gray scale for dummies that I am eagerly waiting for using the Spyder 2 sensor and HCFR (about $70). IMO it’s very easy to set a grayscale and have it push red. An overly red image tends to make people look healthy and we like that, but it is not correct.

The best thing you can do by eye is put up a gray scale ramp with Avia and try to just make it gray with no tint in the colors. I don’t know the G70 jargon but I’m sure someone will as I am only familiar with XG’s.

Mike

**kal** · Posted: Mon Apr 14, 2008 3:54 am Post subject:

I'll cut and paste a section of my "GREYSCALE CALIBRATION FOR DUMMIES" article that I'm working on at the moment. It's about 75% done. There's enough here now for people to get started.

Warning: The work below is still a work in progress... so typo's and and such have not been corrected!

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

Kal I'll be looking forward to reading this about 100 times to commit it to memory Very Happy

Athanasios

**kal** · Posted: Mon Apr 14, 2008 4:16 am Post subject:

Thanks!

I'll be posting the whole thing for review and comments from everyone before I send a newsletter out about it. I want it to be completely polished and painless for everyone.

Kal

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

Kal for Marquee owners ad the term G2 to cutoff and bias.

Athanasios

Gino · Posted: Mon Apr 14, 2008 4:35 am Post subject:

Kal, just an FYI: The name D65 suggests that the correlated color temperature should be 6500K, while in truth it is closer to 6504K.

The CIE 1931 color space chromaticity coordinates of D65 are x=0.31271, y=0.32902

Rec. 709, used in HDTV systems, truncates the CIE 1931 coordinates to x=0.3127, y=0.3290

mike calcott · Joined: 18 May 2006 Posts: 307 Location: Australia

Make it a printable version please

v_erich · Joined: 12 Sep 2006 Posts: 76 Location: Austria/Europe

Great work!
I spent also a few hours on learning the color calibration on my BG808s LC modded and learned, that the original Barco 6500k setting is faaaaar away from grey...

Waiting for the complete article and then start a second round in calibrating.

Regards,
Erich

timbo · Joined: 22 Jul 2007 Posts: 82 Location: Brampton, Ontario

Kal, do you think that the SpyderTV sensor will work for Grayscale Calibration for Dummies or will this dummy need to buy Spyder2 Express?

...and thanks for all of this!

Zebu Fellenz · Joined: 21 Dec 2006 Posts: 2567

Wow,

Thanks guys (Kal), I'm hoping to see this in the next newsletter to read through a couple hundred times and try to understand Wink

**kal** · Posted: Mon Apr 14, 2008 3:24 pm Post subject:

Bruce 09 · Posted: Mon Apr 14, 2008 3:37 pm Post subject:

garyfritz · Joined: 08 Apr 2006 Posts: 12026 Location: Fort Collins, CO

There are many CIE coordinates that "map" to 6500 (as in that CIE chart you posted), but only .3127/.3290 or thereabouts is a "true" 6500. Only coordinates that fall on that curved line accurately represent true color temperatures. Other coordinates in the vicinity can be "mapped" onto a color temperature for convenience, but they do not match up with the colors an idealized black-body will glow at that temperature.

Even if those colors "map" to 6500, it's clear they aren't white. The line on the chart you posted goes from a very distinct green down into pink and even magenta.

Bruce 09 · Posted: Mon Apr 14, 2008 4:02 pm Post subject:

D65 is only one coordinate in the 6500 temperature curvature was what I was trying to clarify .

That Cie chart was only to show that D65 is only one point in the 6500 temperature curve . I never made that chart only linked it .

From Here
http://www.avsforum.com/avs-vb/showthread.php?t=825351&highlight=6500+point

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

garyfritz · Joined: 08 Apr 2006 Posts: 12026 Location: Fort Collins, CO

**kal** · Posted: Mon Apr 14, 2008 6:13 pm Post subject:

The important part is that the newbies will not have to understand any of this when they go to set their greyscale with my procedure. Smile

It certainly helps to understand what's going on of course, but will not be critical.

I will also explain the CIE chart for those that want to understand more, but I won't go into gory details. Consider it optional reading.

Kal

**kal** · Posted: Thu Apr 17, 2008 3:28 pm Post subject:

I spent another 4-5 hours on this in the last day so I thought I'd post what I have so far. See post #3 in this thread http://www.curtpalme.com/forum/viewtopic.php?p=113347#113347

There's enough info in there now for the adventerous people to get started, or to at least read and post comments on what I've written.

Kal

garyfritz · Joined: 08 Apr 2006 Posts: 12026 Location: Fort Collins, CO

Looking very good, Kal! Some comments:

Part 2, ftL target: specify whether the desired ftL level is measured with the sensor pointing at the pj or the screen. Makes a huge difference. (No, a 1.0 gain screen does NOT return 1.0 times as much light as what falls on it!) You tell them to point it at the screen later on, but it's worth mentioning here too.

Step 2.4: Remove the diffuser/filter on the SpyderII. (At least that's my understanding of how it's supposed to be used.)

2.5: Emphasize to use WINDOW, not a full-screen white. CRTs can't display full brightness on the full screen.

2.7: You're not using the black "toilet-paper roll" baffle? Aren't you concerned about the Spyder seeing its multi-colored shadow? Also, I'm surprised that adjusting the angle makes any significant difference in ftL level when pointing at the screen. It should all be pretty uniform.

3.1: That's a very interesting trick to set the 10% ftL level at 0.65% of the 100% level. Never thought of that. By my calculations it should be 0.63%, but that's a quibble. Measuring 0.65 * 100IRE is going to be a bigger problem, though. If you have 12ftL at 100%, then 0.63% is only 0.076 ftL. Will the SpyderII measure accurately that low? Maybe with a long-enough exposure, but even then I doubt it's very accurate at that level. Maybe it would be better to measure at 20% stim and shoot for 2.9% of 100IRE -- 0.35 ftL if 100% is 12 ftL.

Suggestions for part 4:

* Draw a diagram that shows the grayscale response as a straight line, and show that the drive and cutoff basically let you control the upper and lower part of that line. You use that as a 2-point "curve fitting" to get the CRT's response to match the target response as closely as possible. I think a visual analogy like this will help people understand what they're doing a lot better.

* Explain blue hump, blue defocus, etc. http://www.avsforum.com/avs-vb/showthread.php?p=12844360#post12844360

Gary