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3D LUTs for the home enthusiast

 
 
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Author buzzard767
ZRO
#1 | Posted: 29 Sep 2012 21:10 
Hi all. My name is Buzz Schranz and I have a strong interest in 3D LUT production via LightSpace to bring the home theater experience closer to what many of you are seeing in your work environments. As a THX Certified Level 2 Video Calibrator I am familiar with 1D LUT display calibration but I'm a newbie on the 3D LUT learning curve.

LightSpace offers far more tools than needed for my purposes but from what I have learned it can produce exactly the product I'm looking for now that affordable LUT holder/processors like the ee ColorBox and Lumagen Radiance series video processors are being modified to work with this software.

Compared to production and post house duties the needs for the home theater are simple; Rec.709, 3D LUT processed signals for flat panel televisions and projectors. It is in this endeavor that I started this thread and hope to find answers to my questions here.

Author Steve

INF
Male
#2 | Posted: 29 Sep 2012 21:14 
Hi Buzz, welcome to the clan - I'm sure the users here will be of help as best possible.

Ask all and any questions and we will respond as quickly as we can.

Cheers,

Steve
Steve Shaw
Mob Boss at Light Illusion

Author buzzard767
ZRO
#3 | Posted: 1 Oct 2012 18:21 
I'm ready to learn.

First question: I have my LCD display set up with the AVSHD disc black level pattern so that 16 and below are black and 17 and higher are flashing (TV legal). When I put up the Light Illusion BlackCal_Levels.tif I see all of it. I realize that this is what I want to have for LUT production but why is 16/64 and darker visible?

Author Steve

INF
Male
#4 | Posted: 1 Oct 2012 18:27 | Edited by: Steve 
Hi Buzz, that's because the PC HDMI out is remapping the 0-1023 (0-255) range to 64-940 (16-235), as it expected, and as is correct for calibration!

If this wasn't done, the lower blacks from your PC would be clipped on most display.
This is true when using PC for desktop and stills presentation, NOT video footage.
When you use a software DVD player or similar on the PC the DVD window is treated differently by the HDMI signal chain - the same as with normal DVD players.

This is the function of EDID - Extended Display Identification Data - within the HDMI connection.
If you see problems with the levels it is likely the PC or the display is not providing or understanding the EDID correctly.
Placing a Lumagen in the path, and setting the input/output manually - PC or Video - can overcome such problems.

Cheers,

Steve
Steve Shaw
Mob Boss at Light Illusion

Author buzzard767
ZRO
#5 | Posted: 1 Oct 2012 19:59 
I should have said that those signals were output from a WD Live media box direct to the TV.

Author Steve

INF
Male
#6 | Posted: 1 Oct 2012 20:16 
The same is still true... The WD Live Media Box is HDMI EDID compliant, so it know what levels stills and video need to be displayed at.

It's all the same
Steve Shaw
Mob Boss at Light Illusion

Author JJ Johnson
ZRO
#7 | Posted: 1 Oct 2012 22:50 
Steve
Hi Steve and Buzz, JJ here.

Steve,

Can you post a chart of what good color separation of a LCD TV with looks like? Also, I would like to post some color separation charts and graphic LUT images. What would you suggest ... WinZip, drop boxes, html links or maybe just private emails?

As far as what my needs are, I’m looking to calibrate a LUT processor connected to my projector to provide noticeably greater 2D depth and perceived image detail. I want feel more enveloped into the high definition movies I watch, from a visual perspective. As an added bonus, I like to sit somewhat closer to a projector screen with no loss of noticeable detail. No … I don’t like sitting in the front rows at the movie theater ... lol. If home theater projectors are so poorly calibrated today, I see this as a plausible goal.

What do you guys think?

Author Steve

INF
Male
#8 | Posted: 2 Oct 2012 06:44 
Hi JJ, see here http://www.lightillusion.com/idiots_guide.html

There are examples of what you should be getting, as well as bad examples.
This is a work-in-progress page, so not finalised yet.

You can link to images within these forums - the image needs to hosted elsewhere, and then use the 'camera icon' button above the area where you type your message.

Cheers,

Steve
Steve Shaw
Mob Boss at Light Illusion

Author Steve

INF
Male
#9 | Posted: 2 Oct 2012 07:33 
It's probably worth saying something further about RGB Separation...

After calibration the RGB Separation will nearly always be worse as the calibration corrects the underlying colours, which can distort the RGB Separation if the gamut is under range in any area - if the gamut is larger than the target, across the whole range, the RGB Separation will remain good, or at least not get any worse.

But, a raw (uncorrected) display should have near perfect RGB Separation - not having that is a good way to know that the display's internal image processing is not ideal (actually, it means it's bad!).

To check this try profiling a good PC display - a Dell or HP screen for example.
As they have little internal image processing they show what a raw LCD display should really be like
This is quite an eye opener!

Steve
Steve Shaw
Mob Boss at Light Illusion

Author Gabriele Turchi
ZRO
#10 | Posted: 2 Oct 2012 13:29 
hi steve , because you mentioned ""under range in any area"" ,
would't be good add in the quick profile module a quick and explicit way to know if the display we are about to calibrate have poor saturation ?
i had this issue in the past and i did not realized that my saturation was low as starting (and as you told me , the LUT cannot fix that )

thanks
g

Author Steve

INF
Male
#11 | Posted: 2 Oct 2012 13:33 
You can see that very, very easily - in Live measure mode if you put up a 100% colour patch as see where the probe feedback measurement 'cross' is on the Gamut CIE graph, that tells you immediately if the gamut is under or over!!!

Simples
Steve Shaw
Mob Boss at Light Illusion

Author Gabriele Turchi
ZRO
#12 | Posted: 2 Oct 2012 13:36 
Only the 100% ones ?

and would be best have it a bit over (aka over saturate the display a bit (if a Lut will be created )

thanks
g

Author Steve

INF
Male
#13 | Posted: 2 Oct 2012 13:51 
Yes, and yes...

But, doing a Quick Profile to see the full Gamut range is better

Ideally, the display Gamut should be as large as posisble...

See here: http://www.lightillusion.com/idiots_guide.html
Work in progress, so not complete, but it will probably help.

Steve
Steve Shaw
Mob Boss at Light Illusion

Author buzzard767
ZRO
#14 | Posted: 2 Oct 2012 14:45 
Where s the live measure mode accessed?

Author Steve

INF
Male
#15 | Posted: 2 Oct 2012 15:13 
Hi Buzz - within the 'Calibration Interface' use 'Measure/Measure'.
The probe output is then plotted directly on the CIE graph and Luminance thermometer display.

There is a good Guide building here: http://www.lightillusion.com/idiots_guide.html

That should help
Steve Shaw
Mob Boss at Light Illusion

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 3D LUTs for the home enthusiast

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