Calibration Advice Needed for Sharp 70" Setting Primaries - AVS Forum
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post #1 of 10 Old 01-14-2013, 09:52 AM - Thread Starter
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I'm calibrating my Sharp LC-70C8470U TV and could use some guidance.

Thus far, I've got a very good w/b(10 IRE is dE 3.5 the rest are <3), gamma is very flat with an average of 2.2, but I've got a couple of primaries that are being difficult.

dE for Primary/Secondary Colors are as follows:
R 4.7
G 1.5
B 15.3
Y 0.5
C 2.1
M 42.5

Obviously, magenta is the biggest issue, but I think there may be room for improvement. This was about the best I could do with blue, but perhaps with some input both colors can be improved. I'm sure I can dail red in to dE <3.

For Magenta, I chose to set the luminance accurately and do my best to hit the x,y. Which is more important to the dE calculation (Y or x,y)?

For Blue, when I balance R & G, the x,y for B is way off and Y is way too high. When I get close to REC709 for B, it seems to toggle with very little change in Hue.

Also, I've played around with calibrating using 75% saturation windows. I can get the 75% sats to come in accurately, but the primaries are still way off. My understanding is that the primaries are used by the display to create the colors, so I'm confused regarding which method will deliver the best PQ (i.e. the primaries are off, so how can the displya create accurate colors).

Thanks in advance for your input.

BT


Sharp LC-70C8470U
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post #2 of 10 Old 01-14-2013, 10:35 AM - Thread Starter
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Here are some results.







Sharp LC-70C8470U
Onkyo TX-SR606
PS-3
Homegrown HTPC

HCFR 3.0.4.0
i1 Display Pro (i1D3)
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post #3 of 10 Old 01-15-2013, 11:04 AM
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There's no consensus I know of as to whether color luminance errors or color errors are more obvious. I would tend to reduce both errors as much as I could and live with the residual error(s). One thing IS certain... large errors are more likely to be visible than smaller errors. So I try not to leave single large errors even if it means having to make some other error a little larger.

The other thing to keep in mind... green errors are most obvious, blue errors are least obvious... but this is only up to a point. When dealing with "memory colors" like blue sky... blue and cyan errors can be pretty obvious if they are large.

That's a pretty big magenta error... it would be difficult to ignore an error that large in images. Is there another color space option that makes the color space larger so you can avoid the undersaturated blue?

If you have hue, saturation, luminance CMS controls, you may be able to improve Blue by removing some red from it with the hue control... but that might move blue "up" on the graph rather than "out" farther... depends on where the control was set when these measurements were made.

You should be able to make magenta better by adding some green and getting the luminance right and getting red and blue balanced (equal amounts of red and blue).

"Movies is magic..." Van Dyke Parks
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post #4 of 10 Old 01-15-2013, 02:54 PM
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For my experience and my past engineering training, I think that the hue of your color is the most offensive: the eye is trained to see differences, from the gray scale and between two colors, if I have to make an effort I will try to steer the purity where it belong and sacrifice saturation where necessary. If a overall saturation is lacking, let say 5%, you cannot really tell if that is intentional, if a sky or skin tone is leaning to green, your eye will interpret that as an error...
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post #5 of 10 Old 01-15-2013, 07:55 PM - Thread Starter
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Thanks for the responses.

I like the idea of expanding the gamut. This mode does offer expanded gamut, so I'm going to try that. With an expanded gamut, should I use the 75% saturation method or 100% color and set primaries/secondaries?


The cal listed above had very poor blues (appeared much lighter than reference) and was somewhat "pale" overall....skin tones appeared sunburned. I suspect the combination of blue and magenta errors to be the source.

After a lot of very fine tuning, I was able to get the dE's on primaries and secondaries to the following:

R 4.3
G 0.4
B 13
Y 1.6
C 4.2
M 7.5

I ran a 75% sat calibration and the PQ was very good. The dE's for primaries and secondaries is much worse, but PQ much better. I'm amazed at how easy the calibration points are to dial in with this method. http://www.avsforum.com/t/1134710/epson-calibration-guide-1080-1080ub-6100-6500ub-7500ub#post_16166537

Here are the dE results:

R 5.5
G 17.3
B 48.5
Y 5.4
C 9.0
M 40.2

The 75% sats are very accurate, however.

Regards,
BT

Sharp LC-70C8470U
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post #6 of 10 Old 01-18-2013, 05:10 PM
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hi BT,

I need to calibrate my 70" with i1D3 and HCFR as well, so I'd like to learn from you.
If you don't mind:
1. why you set only 124 cd/m ? do you watch it in complete dark room?
I'm more in 140 - 160 range for a day and with lights on
2. how did you setup contrast and brightness and backlight combination? to get your target 124
3. Were you able to move Blue to the target in CIE D65 and how? main is below in magenta zone

thanks
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post #7 of 10 Old 01-19-2013, 01:43 PM - Thread Starter
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Quote:
Originally Posted by mikek753 View Post

hi BT,

I need to calibrate my 70" with i1D3 and HCFR as well, so I'd like to learn from you.
If you don't mind:
1. why you set only 124 cd/m ? do you watch it in complete dark room?
I'm more in 140 - 160 range for a day and with lights on
2. how did you setup contrast and brightness and backlight combination? to get your target 124
3. Were you able to move Blue to the target in CIE D65 and how? main is below in magenta zone

thanks

Hi Mike,

The calibration for dummies guide recommended 30-40 ftL, so I targeted ~38 (on a 100% gray window). I ended up backing down the contrast 1 notch to get a little more control over blue. 124cd/m corresponds to ~36ftL. Brightness was done via the AVS 709 patter for brightness. I set the level to just barely see shade 17. I'll probably set up a boosted brightness for daytime.

I was able to move blue to get my dE's very low and a very flat gamma curve, but as of late, either my i1D3 has shifted or something has changed with the TV. I'm puzzled.

Regards,
BT

Sharp LC-70C8470U
Onkyo TX-SR606
PS-3
Homegrown HTPC

HCFR 3.0.4.0
i1 Display Pro (i1D3)
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post #8 of 10 Old 01-31-2013, 03:06 PM
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Quote:
Originally Posted by Basstrix View Post

Hi Mike,

The calibration for dummies guide recommended 30-40 ftL, so I targeted ~38 (on a 100% gray window). I ended up backing down the contrast 1 notch to get a little more control over blue. 124cd/m corresponds to ~36ftL. Brightness was done via the AVS 709 patter for brightness. I set the level to just barely see shade 17. I'll probably set up a boosted brightness for daytime.

I was able to move blue to get my dE's very low and a very flat gamma curve, but as of late, either my i1D3 has shifted or something has changed with the TV. I'm puzzled.

Regards,
BT

thanks for the answer.
Yes, I understand about brightness and contract to set it by blinking rows pattern, but I'm not sure about backlight setting for this matter.
Do you set backlight to get targed 40 ftL?

How do you know that HCFR gets / shows correct numbers?
Is there a way to calibrate or measure i1D3 with HCFR?
Do you have any corrections for the i1D3 set in sensor matrix table?

Is there a way to validate what i1D3 reads in iProfile (X-Rite) vs HCFR?

How to keep gamma horizontal?
When I get good RGB my gamma dives.

How to know target cd/m for each gray to make it closer to the target while RGB all close 100%?
This is when I adjust all 3 primaries up or down so resulting cd/m is impacted. I mean, how to get compromise between aligned RGB and flat at 2.2 gamma?

I got better RGB, but worse gamma or better and flat gamma and not perfect RGB.

Thanks.
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post #9 of 10 Old 02-01-2013, 10:15 AM
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There is no one answer to the question you have about how to set the backlight... it all depends...

The lowest possible backlight setting produces the darkest blacks and that's one of the most desirable characteristics for a video display... but... there's always one of those... many TVs get into weirdness when you set the backlight too low and you can't really calibrate the TV to be accurate so you have to use some setting higher than the minimum setting just to keep the TV from looking odd. It is very difficult to tell when the TV is misbehaving due to a too-low backlight setting without test patterns and a meter.

Next, you want 30-40 fL for 100% white in a dark room... I prefer about 32-33 fL. With the backlight at the lowest setting, you may not be able to achieve ~35 fL and you'll have to raise the Backlight setting even though that also raises the black level.

Contrast (the control in the user menu) is also a factor in achieving ~35 fL in a dark room. You want Contrast high enough to achieve your ~35 fL goal but not so high that you completely clip every step above digital 235, and especially so that you do not clip any steps below 235. The problem with this is that you don't know what ~35 fL is unless you have a meter and software. Without a meter, the only clue you have to how close you are to a good Contrast setting is to evaluate your eyestrain level after watching a movie for 2 hours in a dark room. If you have eyestrain, the TV is too bright. If you have no eyestrain, raise the backlight/Contrast incrementally until you experience eyestrain, then back-off just enough that the eyestrain drops-off.

Finally, you have to find a combination of lowest backlight setting possible and proper Contrast setting to get the darkest blacks you can (the Brightness control is also involved in the black level, assuming this is fairly straightforward for you to set with a PLUGE pattern). But keep in mind that the Brightness setting may change if you increase or decrease Backlight or Contrast... always double-check after changing other settings.

"Movies is magic..." Van Dyke Parks
THX Certified Professional Video Calibration
ISF -- HAA -- www.dBtheatrical.com
Widescreen Review -- Home Theater & Sound
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post #10 of 10 Old 02-01-2013, 08:18 PM
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^

I like the post above however I like a more gentle image and 30fl in a dim condition.
In a dark condition I like more like 25fl...

Just a personal preference.

-Walter
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