Calibrators... Lets Talk Shadow Detail. - AVS Forum
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post #1 of 18 Old 03-31-2013, 07:58 AM - Thread Starter
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First 2 questions on test patterns.

Test Patterns:

1. Should be able to seen video level 17 (Should not be able to see video level 16.) Lets agree on this correct?

2. Gamma should be between 2.22 and 2.5 for the entire range, Correct?

The end result should be every detail visible in the shadows correct?

WRONG!!!!, and this is what I am trying to figure out with this post.




Here are some real world test pictures that are difficult for most displays to display correctly.

I am trying to see if there is a solution for the problem on most displays, if at all without washing out the picture.

*If your display you are viewing on is great at shadow detail you will see the details I have circled in red on the over exposed pictures. If you can not see them on the normal picture, then your display is not great at shadow detail.*

Real World:

Normal:


Overexposed:


Normal:


Overexposed:


Normal:


Overexposed:




So here is what I am trying to solve...

I have a Pioneer Kuro 111FD in the living room and a JVC RS4810 in the theater room

The kuro shows all the shadow detail perfectly in all the above shots.
The JVC does not




To add even more ??? to the whole approach...

The JVC "calibrated" on the test pattern "CAN" show video level 17
The Kuro "calibrated" on the test pattern "CAN'T" show video level 17

So you are reading this right... the Kuro "CAN'T" show video level 17 but the JVC "CAN", but the Kuro still has more shadow detail... Mind boggling.



I can get the JVC to have the shadow detail by lowering gamma at 5%. But as soon as I get to the point I can bring out the detail the image is washed out and flat in brighter scenes.

I even used a Lumagen to find out what gamma level effects the details the most, and it is 1%. But even still adjusting that still washes out the image to some degree.
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post #2 of 18 Old 03-31-2013, 10:30 PM
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Welcome to the world of consumer video displays. You have experienced reality as it exists today and as it has always existed in the world of consumer video displays. Test patterns don't tell the whole story. Test patterns don't always provide the optimum setting you are looking for. Test patterns don't always reveal how images will look when displayed because dynamic moving images may be processed differently (internal to the video display) than static test pattern images.

The gamma used by the people doing final approval for movies released on Blu-ray disc are using gammas in the range of 2.2-2.3. The whole 2.5 thing just WILL NOT die out even though it is NOT USED. Gamma set to 2.4 or 2.5 makes all the midtones much darker than they should be and actually makes the feeling of depth worse, not better. Gammas lower (numerically) than 2.2 make images look flat and milky because the midtones are too bright. People are all wrapped around the axle about how gamma affects shadows... and that is one concern, but you can't ignore midtone appearance and midtones and apparent depth in images looks best when gamma is in the 2.2-2.3 range. If you an set 2.25 for the gamma target and keep all the grayscale steps within the 2.2-2.3 range, you'll have great looking images and you will see the right amount of detail. If you set gamma to a numerically higher value (like 2.4 or 2.5), shadows will stay too dark too long.

You may also have some innocent-sounding control set to "on" or some other setting and that control might be messing with your gamma (darkening shadows). Most test patterns that show digital levels, like levels 0 - 25, for example, have no white in the pattern at all. Some video displays process frames like that VERY differently than they process frames with a wider range of luminance levels. That alone is enough to make the test pattern setting invalid.

When a test pattern setting produces an undesirable result, the right thing to do is ignore the test pattern setting and change the setting until the images look right (assuming you haven't enabled (or forgot about) some setting that is causing the display to respond unpredictably). All the samples you show have bright or relatively bright features in them that the digital levels test pattern probably did not have. It's likely that the JVC projector has some setting enabled that should not be enabled or that you need a modified digital levels test pattern that has a wider range of luminance values on it. By the way... cranking brightness up to show emphasized shadow detail kind of defeats how your vision system works. Images with very bright areas tend to mask the visibility of shadow detail. Human vision, at any one iris opening, has a range claimed to be between about 500:1 and 1000:1 depending on where you read about it. Modern video displays often can produce a dynamic range of 2000:1 or higher. Bright areas in images will cause the iris in your eye to close somewhat while dim images with nothing bright in them will cause the iris in your eye to open fully to see the dark images better. You can't stop the iris in your eye from doing that. That's why you may get a very different result using a test pattern that has some brighter areas in it along with the 0-25 levels patches. This is a complex topic and you are making it even MORE complex by comparing flat panel images to projector images where things can be very different visually because of the amount of "black" (presuming the room is dark) around the images and how bright 100% white is. The projected image may measure 16 fL for 100% white while the flat panel display may have 100% white at 35 fL. Is the flat panel display brighter or dimmer? Well, the peak measured level for 100% white isn't necessarily the sole determiner in answering "which is brighter?" because you may need to look at measuring the total amount of light produced by the display. If the projector's screen is physically much larger than the panel display, the total amount of light reflected from the projector screen could be higher than the measurement of 100% white might lead you to believe. Plasma TVs also have automatic brightness limiting which does not exist in the JVC projector - that one different alone makes direct comparisons VERY tricky at best.

So you can see... the variables are HUGE. And simple test patterns can't always be trusted.
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post #3 of 18 Old 04-01-2013, 04:26 AM
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This is an interesting topic and what you have said Doug makes sense to me. I'm no expert and have only just begun diy calibration for myself using chromapure. I've had the issue of trying to get rid of the washed out milky mid tones while keeping dark blacks on my LCD tv. At present I have the mid tones looking very good but the black levels are just too black for my liking. Need more picture brightness overall. My gamma is 2.2 average but i'll try your suggestion of 2.25 target with 2.2/2.3 level settings. As I'm still learning I've a few other options to try but what you said is how I'm seeing it.

Thanks for your 'real world' explanation!
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post #4 of 18 Old 04-01-2013, 05:38 AM
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Quote:
Originally Posted by dreameruk View Post

This is an interesting topic and what you have said Doug makes sense to me. I'm no expert and have only just begun diy calibration for myself using chromapure. I've had the issue of trying to get rid of the washed out milky mid tones while keeping dark blacks on my LCD tv. At present I have the mid tones looking very good but the black levels are just too black for my liking. Need more picture brightness overall. My gamma is 2.2 average but i'll try your suggestion of 2.25 target with 2.2/2.3 level settings. As I'm still learning I've a few other options to try but what you said is how I'm seeing it.

Thanks for your 'real world' explanation!

Try This:

Set your Display Brighness @ 0 and measure a Black Pattern, write down the Luminance... Check What Bar Is Flashing using AVSHD Brighness Pattern.

When Add +1 To your Brighness and measure again the Black Pattern, also check the Flashing Bars again....

Is the Black Luminance the same or your Black's luminance is higher with the +1 of your Brighness?

If the 2 readings are similar when add another +1 to brighness again... We don't want any increase of your Black Luminance level.... Set your Brighness there you have lower Black Luminance and more Bars flashing the same time. wink.gif

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post #5 of 18 Old 04-01-2013, 06:33 AM - Thread Starter
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Doug I also agree gamma 2.22 is what should be used exclusively. I only put 2.5 in there for the calibrators that "know" better then us... wink.gif

I will say my compairison between plasma and front projector is not the best, but some DLP projectors are amazing at showing the details as well. So it's more then just front projector vs flat panel. I was using that as an extreme example.
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post #6 of 18 Old 04-01-2013, 07:57 AM
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Thanks for that tip connecTEDD and to you SOWK for highlighting this observation. I know what to be looking out for in my next TV/projector!
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post #7 of 18 Old 04-01-2013, 08:34 AM
 
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SOWK, with the JVC at 2.2 it is not going to show shadow detail as good as Kuro but can come very close. Do not hesitate to make some adjustments to the custom gamma down low in the 5-15% range to help bring out this detail, just don't over do it so you still maintain that depth.
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post #8 of 18 Old 04-01-2013, 10:05 AM - Thread Starter
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I have, but to get the detail out of the shadows kills the over all pic in brighter scenes. The JVC would need adjustments at about 1% to do it correctly.
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post #9 of 18 Old 04-01-2013, 11:50 AM
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You have too lose some shadow detail to make the picture look right.
I noticed when the sun and room were brighter that I was getting the milky blacks.
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post #10 of 18 Old 04-01-2013, 01:25 PM
 
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SOWK have you went in and adjust the 5-15% individually on the graph? I have gotten pretty good results with the JVC, you should be able to get a good improvement. It might throw off your average gamma reading but most will appreciate the results.
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post #11 of 18 Old 04-01-2013, 03:39 PM
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One thing you can do in CalMAN is go in to the levels editor and create a set of levels that have 1% or even 1 bit steps to really see how a display comes out of black.

In order to really see the data correctly you'd still need to read 100% white, which means you need to set custom ranges for the chart axis.

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post #12 of 18 Old 04-01-2013, 04:29 PM
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Quote:
Originally Posted by Doug Blackburn View Post

Welcome to the world of consumer video displays. You have experienced reality as it exists today and as it has always existed in the world of consumer video displays. Test patterns don't tell the whole story. Test patterns don't always provide the optimum setting you are looking for. Test patterns don't always reveal how images will look when displayed because dynamic moving images may be processed differently (internal to the video display) than static test pattern images.

The gamma used by the people doing final approval for movies released on Blu-ray disc are using gammas in the range of 2.2-2.3. The whole 2.5 thing just WILL NOT die out even though it is NOT USED. Gamma set to 2.4 or 2.5 makes all the midtones much darker than they should be and actually makes the feeling of depth worse, not better. Gammas lower (numerically) than 2.2 make images look flat and milky because the midtones are too bright. People are all wrapped around the axle about how gamma affects shadows... and that is one concern, but you can't ignore midtone appearance and midtones and apparent depth in images looks best when gamma is in the 2.2-2.3 range. If you an set 2.25 for the gamma target and keep all the grayscale steps within the 2.2-2.3 range, you'll have great looking images and you will see the right amount of detail. If you set gamma to a numerically higher value (like 2.4 or 2.5), shadows will stay too dark too long.

You may also have some innocent-sounding control set to "on" or some other setting and that control might be messing with your gamma (darkening shadows). Most test patterns that show digital levels, like levels 0 - 25, for example, have no white in the pattern at all. Some video displays process frames like that VERY differently than they process frames with a wider range of luminance levels. That alone is enough to make the test pattern setting invalid.

When a test pattern setting produces an undesirable result, the right thing to do is ignore the test pattern setting and change the setting until the images look right (assuming you haven't enabled (or forgot about) some setting that is causing the display to respond unpredictably). All the samples you show have bright or relatively bright features in them that the digital levels test pattern probably did not have. It's likely that the JVC projector has some setting enabled that should not be enabled or that you need a modified digital levels test pattern that has a wider range of luminance values on it. By the way... cranking brightness up to show emphasized shadow detail kind of defeats how your vision system works. Images with very bright areas tend to mask the visibility of shadow detail. Human vision, at any one iris opening, has a range claimed to be between about 500:1 and 1000:1 depending on where you read about it. Modern video displays often can produce a dynamic range of 2000:1 or higher. Bright areas in images will cause the iris in your eye to close somewhat while dim images with nothing bright in them will cause the iris in your eye to open fully to see the dark images better. You can't stop the iris in your eye from doing that. That's why you may get a very different result using a test pattern that has some brighter areas in it along with the 0-25 levels patches. This is a complex topic and you are making it even MORE complex by comparing flat panel images to projector images where things can be very different visually because of the amount of "black" (presuming the room is dark) around the images and how bright 100% white is. The projected image may measure 16 fL for 100% white while the flat panel display may have 100% white at 35 fL. Is the flat panel display brighter or dimmer? Well, the peak measured level for 100% white isn't necessarily the sole determiner in answering "which is brighter?" because you may need to look at measuring the total amount of light produced by the display. If the projector's screen is physically much larger than the panel display, the total amount of light reflected from the projector screen could be higher than the measurement of 100% white might lead you to believe. Plasma TVs also have automatic brightness limiting which does not exist in the JVC projector - that one different alone makes direct comparisons VERY tricky at best.

So you can see... the variables are HUGE. And simple test patterns can't always be trusted.

thanks for the thoughtful post! Are you using power gamma 2.25 or BT 1886?

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post #13 of 18 Old 04-01-2013, 10:28 PM
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Quote:
Originally Posted by Doug Blackburn View Post

...
Images with very bright areas tend to mask the visibility of shadow detail. Human vision, at any one iris opening, has a range claimed to be between about 500:1 and 1000:1 depending on where you read about it. Modern video displays often can produce a dynamic range of 2000:1 or higher. Bright areas in images will cause the iris in your eye to close somewhat while dim images with nothing bright in them will cause the iris in your eye to open fully to see the dark images better. You can't stop the iris in your eye from doing that. That's why you may get a very different result using a test pattern that has some brighter areas in it along with the 0-25 levels patches.
...

This subject interests me greatly too. I have the same trouble as SOWK and have found that dialing the 5% point down to 0.5% works well for me to bring out the missing shadow detail. I'm going to try his 1% out of curiosity.

Your point above makes total sense except that when watching 2.35 material on my 16:9 screen I can still see the black bar's illumination and the shadow detail is still missing. If I can see those blackest blacks have illumination and still not see the shadow detail, what's going on??
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post #14 of 18 Old 04-02-2013, 03:36 AM
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I run at 1% in my Lumagen with an X35 since I found that using 0.5 raised the black level. Using 1% seems a happy medium since it doesn't seem to raise the black floor, yet can make the 17 flashing bar more visible than it otherwise would be. I then use the JVC's 5% control to make any further adjustments if changing the Lumagen's control from 5 to 1% causes any side effects (doesn't seem to though). I aim for gamma of 2.0 at 5% and 2.1 at 10% rising up to 2.25 at and above 20%. However, my room currently isn't ideal so I know that adding dark surrounding to the screen area will give more improvement since it's easy to wash out shadow detail as my room is currently.

I also found that raising the Lumagen's Luma too high when using the 1% setting caused a colour shift to the 17,18 & 19 flashing black bars so further tweaking might be needed and it's too dark to measure very well even with a D3, so I had to do this by eye.

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post #15 of 18 Old 04-02-2013, 07:57 AM
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Quote:
Originally Posted by erkq View Post

This subject interests me greatly too. I have the same trouble as SOWK and have found that dialing the 5% point down to 0.5% works well for me to bring out the missing shadow detail. I'm going to try his 1% out of curiosity.

Your point above makes total sense except that when watching 2.35 material on my 16:9 screen I can still see the black bar's illumination and the shadow detail is still missing. If I can see those blackest blacks have illumination and still not see the shadow detail, what's going on??

your display probably needs a higher native contrast ratio to properly display shadow details without washing out the picture by dropping point gamma too much or raising brightness/black level

try a 2.2 gamma if you are using something closer to 2.3 or 2.4
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post #16 of 18 Old 04-02-2013, 09:08 AM
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Yes, I am at a beautiful 2.3! smile.gif It has drifted up from 2.2 for some reason. I'll bring it back to 2.2 since that seems to be the emerging consensus too.

I run with the iris all the way open to light up a 120" wide 16:9 AT screen, so my measured "real world" cr is a consistent 24k:1.

Thanks for the info, and thanks for the details, Kelvin. I'll try the 1% point since you are the second person to have settled on that. I find my blacks are as black as the black bars at 0.5% but experimentation is good.
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post #17 of 18 Old 04-02-2013, 09:21 AM
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Could this be just a case of lumen output? The brighter the image, the more detail you'll see? 15 fl vs. 30 fl?
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post #18 of 18 Old 04-02-2013, 09:53 AM
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Quote:
Originally Posted by Crabalocker View Post

Could this be just a case of lumen output? The brighter the image, the more detail you'll see? 15 fl vs. 30 fl?

If you're talking to me, my confusion comes in that I can see the blackest black the projector is capable of. You know that "shadow-puppet test" that all digital projectors fail? Well... mine fails too. I can see shadow puppets in the black bars and at the same time not see shadow detail in the picture. I haven't had a chance to play with the 1% point yet though.
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