Need a little grayscale help with Sony LCD - AVS Forum
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post #1 of 11 Old 12-22-2008, 05:44 PM - Thread Starter
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PLEASE SEE POST #5 for calibration charts.



I'm using HCFR and iOne colorimeter to calibrate a Sony XBR8. Irrespective of where I set the IRE100% using contrast setting, I can't get the IRE10% to 0.65% without washing out the blacks. With the below black bar on DVE just invisible, I get in the area of 0.15fL as opposed to .24fL. This would be expected from the display which has a low gamma. Otherwise, between 20 and 90 IRE, everything is spot on.

My question is how to most appropriately address this. Should I do all of the grayscale adjustments/iterations first, then reset the brightness by eye, to make the below black disappear, or vice versa?
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post #2 of 11 Old 12-22-2008, 05:54 PM
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Don't obsess over a single value.

Almost every display has some tradeoff that you need to make/accept.

If everything else is OK and all that's "wrong" is the value for 10%, don't sweat it.
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post #3 of 11 Old 12-22-2008, 07:23 PM
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Tom meantions this in his Calibration guide. I guess if you crush blacks by using the 10 IRE percentage of 100 IRE trick, your set cannot maintain a flat 2.2 gamma. So in this case, just do the pluge thing and make sure you at least hide the below black and make the 2% bar *just* visible.

In the case of my set... I have not yet done my greyscale. My gamma number is low at 10 IRE and high at 100 and the average is 2.2


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post #4 of 11 Old 12-23-2008, 08:14 AM - Thread Starter
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Quote:
Originally Posted by cvearl View Post

Tom meantions this in his Calibration guide. I guess if you crush blacks by using the 10 IRE percentage of 100 IRE trick, your set cannot maintain a flat 2.2 gamma. So in this case, just do the pluge thing and make sure you at least hide the below black and make the 2% bar *just* visible.

In the case of my set... I have not yet done my greyscale. My gamma number is low at 10 IRE and high at 100 and the average is 2.2

Yes, this is what I took from the guide as well, but I wasn't sure whether it was technically more appropriate to adjust the grayscale before resetting the brightness by "eye" or to adjust the brightness first, then do the rest of the grayscale. I also read conflicting opinions about whether IRE100% should be in the 30-40fL range or 50-60fL range for an LCD, but I suppose that I can go as high as possible, so long as I don't run out of any colors.

For what it's worth, precalibration, my gamma is 2.3 or higher for IRE20% or lower and below 2.1 in the midrange. 2.3 is probably still pretty good. After calibration, it's almost exactly 2.2 at 10%, but as I said, it's way to washed out, and it looks much better with the precalibration settings. The problem precalibration is that my deltaE's were 12 or higher across the board. After calibration, they are still very high in the low end.

I'll have to go back and redo everything from the start, since I watched The Dark Knight last night, and I could not have watched it as the Not So Dark Knight, so I restored everything to my recalibration settings.
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post #5 of 11 Old 12-23-2008, 03:11 PM - Thread Starter
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I set the contrast to 39-40 fL at IRE100 and set the brightness so the below black disappears (about .44% at IRE10). Used IRE30 and IRE80 to adjust white balance.
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post #6 of 11 Old 12-25-2008, 08:25 AM - Thread Starter
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post #7 of 11 Old 12-25-2008, 12:12 PM
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Merry Christmas!

Did you adjust your backlight at all? I would use backlight to get your FL in the ballpark of 40 and then adjust contrast.

I haven't used ColorHCFR (I use Calman). Using Calman I first adjust backlight to get 100ire at a little above 40FL. Then I use the luminance curve reading. Take a reading at 100ire, then take readings at 90ire and adjust contrast until it is on the curve. Then take readings at 20 ire and adjust brightness so it is on the curve.

Now take a complete reading and see how it looks. It should be pretty good if you were able to get 20 and 90 lined up.

Now go and do your greyscale adjustments. If you have a lower and upper RGB adjustment then use 30ire and 80ire. If you only have one RGB adjustment(I did) adjust it so 50/60 ire is spot on and this should give you the best results across the board.

After you have your greyscale setup now you want to set your color adjustment. Take a reading of 75ire and take note of the FL reading. Now take a reading of 75% red and take note of the FL reading. Adjust the color so that the FL reading on red is 21.26% of the the white.

After this is complete, now take measurements of magenta and cyan. Use tint to bring them to the lowest delta E. Note that one setting may get you the best results for magenta and not cyan or vice versa. Use the setting that gets them both equally low. You don't want one really low and the other way off.

Now you can go take a complete reading of all the colors and see how it comes out. You will now want to go back and check both your contrast/brightness and your greyscale settings as mentioned above to see if it has changed.

Once you make the final adjustments to your liking congratulations you are done for the most part except for sharpness if you haven't set that yet. Now it is possible you will have finer CMS adjustments and you would make use of those accordingly.

From what I have been told, ColorHCFR doesn't have this luminance reading option unless you take a complete greyscale reading.

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post #8 of 11 Old 12-25-2008, 03:34 PM
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Quote:
Originally Posted by jsteinhauer View Post

I set the contrast to 39-40 fL at IRE100 and set the brightness so the below black disappears (about .44% at IRE10). Used IRE30 and IRE80 to adjust white balance.

If you want your black level to increase less than one step of 'Brightness'
you could try to increase each of the Red Green Blue "brightness"/"bias" greyscale/whitebalance
settings one or two steps up.
I would use IRE20 and IRE70 as the main points for calibration.
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post #9 of 11 Old 12-26-2008, 04:25 AM - Thread Starter
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Quote:
Originally Posted by dachness View Post

Merry Christmas!

Did you adjust your backlight at all? I would use backlight to get your FL in the ballpark of 40 and then adjust contrast.

I haven't used ColorHCFR (I use Calman). Using Calman I first adjust backlight to get 100ire at a little above 40FL. Then I use the luminance curve reading. Take a reading at 100ire, then take readings at 90ire and adjust contrast until it is on the curve. Then take readings at 20 ire and adjust brightness so it is on the curve.

Daniel

This is a different way to initially set the grayscale than either of the methods I read, but I coud try it. I must admit, though, not having tried this, I am suspicious that increasing the backlight will adversely impact the picture in a dark environment. Where should the brightness be set before changing the backlight to achieve 40fL at IRE100? I use minimum backlight for the current set of readings. Current product reviewers chose higher backlight levels, but did not describe their viewing environments, if I recollect.

Quote:
Originally Posted by rickardl View Post

If you want your black level to increase less than one step of 'Brightness'
you could try to increase each of the Red Green Blue "brightness"/"bias" greyscale/whitebalance
settings one or two steps up.
I would use IRE20 and IRE70 as the main points for calibration.

I never thought of using RGB bias to change the "brightness". I will look into this. Other methods I have seen used IRE30 and either IRE80 or IRE90 for the main points. I am not sure using 70 instead of 80 will help me, as color tracks pretty well to the high end. Am I wrong? Using IRE20 might help, BUT I wonder whether this is getting low enough where the colorimeter starts to lose accuracy?

Thank you for the feedback. You have both provided food for thought.
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post #10 of 11 Old 12-26-2008, 06:46 AM
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Quote:
Originally Posted by jsteinhauer View Post

I never thought of using RGB bias to change the "brightness". I will look into this. Other methods I have seen used IRE30 and either IRE80 or IRE90 for the main points. I am not sure using 70 instead of 80 will help me, as color tracks pretty well to the high end. Am I wrong? Using IRE20 might help, BUT I wonder whether this is getting low enough where the colorimeter starts to lose accuracy?

20% should be fine with your meter. Down at 10% you might not want to use it for greyscale but for luminance readings at 10%, it should be ok.
This is from Tom Huffman's guide:
Basic Guide to Color Calibration using a CMS (updated and enhanced)
Sometimes you may find that even though 90 and 30 IRE are neutral gray, the mid range 50-70 IRE is not. This means that your display won't track a good gray scale and you have to make some compromises. The general rule of thumb is to focus on getting the mid range to track neutral gray. Then get the low end right. Sacrifice accuracy at the top end if you have to.
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post #11 of 11 Old 12-26-2008, 10:29 AM
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Contrast will affect FL light output. Backlight will also affect FL light output. As you can see they will both effect each other.

I am not sure how far off you contrast is from the default. In my case I left it at the default adjusted backlight to get around 40FL the did the adjustment mentioned above to set contrast and brightness. Then afterwards when contrast and brightness are spot on, I adjust backlight again to get the desired FL at 100ire. This as 40 FL for me since I use bias lighting for night
Time viewing. If your primry viewing environment is dark then you will not want it at 40FL as eye strain will occur. I don't remember the exact numbers for bat cave viewing but if I remember correctly it could be as low as 13-15 FL. If this is your target then you would adjust backlight to that level instead of 40.

If you end up turning backlight all the way down and you're FL is still above target, then you will need to lower contrast until you achieve your desired FL level.

As you mentioned generally the lower your backlight is set the better blacks will look. You should also look into bias lighting/ideal lume which improves percieved picture quality in bat cave envionments.
Regarding using different points for greyscale measurements, if you want to be really thorough you could do both and see which provides the most linear results across the board. Using greyscale at 20ire is essentially the same thing as what as mentioned to increase the lower end light output.
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