Calibration of white-levels of Samsung F8500 using AVS 709 - AVS Forum
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post #1 of 10 Old 06-18-2014, 11:03 AM - Thread Starter
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Calibration of white-levels of Samsung F8500 using AVS 709

Hi,

I am unable to correctly calibrate the white levels of my Samsung F8500 50 inch television using the basic AVS 709 basic setup. So the problem is that I'm unable to create a uniform reference white area without making the blacks too bright. I'm using the Movie picture mode as my starting point.

Any idea what I'm doing wrong?

Thanks,
Peter

PS: My Pioneer Blueray player is directly connected to the TV and I managed to correctly calibrate my Sonia Bravia using the same method, so it's not the BD player.
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post #2 of 10 Old 06-18-2014, 11:07 AM
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What WTW level are you shooting for ? 235 240 245 250 255 ? I think the consensus for your set is a contrast of 95 then use the Cell light control to obtain the desired light output

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post #3 of 10 Old 06-18-2014, 11:49 AM - Thread Starter
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Originally Posted by chunon View Post
What WTW level are you shooting for ? 235 240 245 250 255 ? I think the consensus for your set is a contrast of 95 then use the Cell light control to obtain the desired light output
Thanks for your reply. I apologize if I say something silly here... I do not remember the exact numbers, for starters, I just wanted to make everything white to the right of the vertical text that says "reference white" and could hardly make any flashing bars disappear in that area. If I remember correctly (I'm not around the TV right now), I could only make about 5 bars disappear on the extreme right of the screen. I will verify this when I get home.
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post #4 of 10 Old 06-18-2014, 12:50 PM
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Reportedly the F8500 doesn't clip whites no matter how high you set the contrast. Just set it to 95 so the 10 point white balance lines up correctly.
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post #5 of 10 Old 06-18-2014, 01:08 PM - Thread Starter
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Originally Posted by Stereodude View Post
Reportedly the F8500 doesn't clip whites no matter how high you set the contrast. Just set it to 95 so the 10 point white balance lines up correctly.
Thanks, that's very interesting! Is this a problem for some situation (I'm interested in watching movies)? What is the rationale behind clipping the whites using the calibration images?
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post #6 of 10 Old 06-18-2014, 01:53 PM
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Originally Posted by peti8500 View Post
Thanks, that's very interesting! Is this a problem for some situation (I'm interested in watching movies)? What is the rationale behind clipping the whites using the calibration images?
The proper YCbCr video format used by nearly all CE devices specifies that black is 16 and white is 235. The idea behind the patterns is to help you you set 16 to black and 235 to white. Some displays clip levels above 235 and below 16. However, some digital displays do not clip any white level, they will attempt to display them and instead experience a color shift in white when they can not product any more luminance from one or two of the RGB components that make up white. In these cases you really need a meter to find the white luminance you're targeting (like 120cd/m^2) or the contrast setting where you are getting as much brightness as possible without experiencing a color shift.
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post #7 of 10 Old 06-18-2014, 04:18 PM
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Quote:
Originally Posted by peti8500 View Post
Thanks, that's very interesting! Is this a problem for some situation (I'm interested in watching movies)? What is the rationale behind clipping the whites using the calibration images?
Reduce Contrast if clipping occurs below 235. If you the see the bars above 235 that's fine and in that case use Contrast to set the luminance level comfortable for viewing in your environment. Once accomplished, go back and use the pluge pattern to recheck black level 16 with the Brightness control.

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post #8 of 10 Old 06-18-2014, 09:40 PM
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contrast of 100 on mine basically clips nothing as well. i still ended up using a contrast of 95 since that seems to be what it was 'designed' for. i don't fully understand it, but there seems to be some issue with the 10pt calibration shifting if the contrast is set much higher or lower than 95.


it's fine for me, as even after all that, i still found it necessary to turn on the eco mode to reduce brightness to a comfortable level.


i seem to be wrong every time i think i know what I'm talking about, but i always thought the idea of setting contrast so that whites 'clipped' at around 235 was to get the maximum brightness, and therefore maximum contrast when displaying a video signal. i mean, if nothing is ever encoded above 235, then you'd want 235 to be the max for your display. with the f8500 being able to show 'whiter than white' you end up with a dimmer image. much like if you set brightness so that black levels below 16 are visible, you'll end up with an image that's too bright. or so i THINK, haha. but with the f8500 especially, there's no need as it's crazy bright anyway. so it makes sense to not really worry about where white is clipping(as long as it's at least 235) and set the contrast to level that gives you your preferred brightness.
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post #9 of 10 Old 06-19-2014, 02:54 AM
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This text from Spears&Munsil sums it up quite good. My underlining.

One important thing that we haven’t yet mentioned is that the video system has two different white levels. The white level that is talked about most often is “reference white.” Reference white is the top of the nominal video range. However, there is room in the video standard for above-reference values, which are sometimes called “whiter than white” or “super white.” This area of the video range is supposed to be reserved for “overshoots” and occasional excursions outside the nominal range. Very little of most video frames strays outside the reference range, but often the stuff that does stray outside the range makes a difference in the image. Most notably, when displaying bright saturated colors and/or highlights on bright white and near-white objects, one or more of the red, green, or blue channels may stray into the overshoot area. For this reason, professional video monitors are always calibrated such that they have room to display the above-reference range.

This is the basic quandary: if you calibrate so that reference white is the brightest level the display can produce, you maximize the contrast ratio, which is measured by comparing reference white to reference black. But you may be missing some amount of picture information, albeit small, that the professionals working on the video saw.

How exactly to resolve this quandary involves considering what you consider most important and what your viewing conditions are. If what you want is the punchiest possible video, or you routinely watch video in a room with a significant amount of light, you may want to consider deliberately calibrating to maximize reference white and clipping the above-reference range. If you want to make your display look as much like the pro monitors used to master video, and you’re viewing the video in a dim or dark room, you’ll almost certainly want to preserve the above-reference range.

You can split the difference if you like. Each additional chunk of brightness above reference white adds a little bit less to the image than the previous chunk, so you might decide to preserve some of the above-reference range but not all. This isn’t inherently wrong. However, it’s worth noting that we nearly always calibrate our displays to preserve the entire above-reference range. We think that most modern displays have enough inherent contrast that sacrificing a small part of it to the above-reference range is worthwhile
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post #10 of 10 Old 06-21-2014, 02:13 PM
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My set starting clipping at 96 so like mentioned, 95 was the sweet spot. Your brightness should be around 46-49.

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