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Discussion Starter · #1 ·
Hi all,


I have come accross threads and posts from many "pro" calibrations where the contrast setting is VERY low, even on my TV 55LH90 model. One person stated his contrast was at "81" which when I set my TV to 81, the contrast bars are visible up to the 250's. So, that has GOT to be wrong. Not only that but he quoted a backlight setting of "30" which again is ridiculously low. My question here is, would there be ANY situation with setting the gamma and color where a calibrator would be forced to drop the contrast that low? I have my doubts, but I'm no calibrator so, I would like to know what's up with calibrators setting TV contrast so low that they are FAR off on contrast accuracy (according to the standard reverse ramp grayscale contrast pattern). This concerns me because I want to have a professional calibration done, but I'm having my doubts if many calibrators are accurately setting contrast. I don't want to have any doubts before I drop $400 and permanently change my ISF preset settings. Could someone explain this to me?


I just want to express that I like a bright picture and calibration seems like it's going to make my TV look a bit washed out and foggy with the low contrast. I want to avoid this but I'm willing to understand or compromise if accuracy in gamma or color is compromised when using a nice bright contrast setting.
 

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Quote:
Originally Posted by Timothy91 /forum/post/20866485


Hi all,


I have come accross threads and posts from many "pro" calibrations where the contrast setting is VERY low, even on my TV 55LH90 model. One person stated his contrast was at "81" which when I set my TV to 81, the contrast bars are visible up to the 250's. So, that has GOT to be wrong. Not only that but he quoted a backlight setting of "30" which again is ridiculously low. My question here is, would there be ANY situation with setting the gamma and color where a calibrator would be forced to drop the contrast that low? I have my doubts, but I'm no calibrator so, I would like to know what's up with calibrators setting TV contrast so low that they are FAR off on contrast accuracy (according to the standard reverse ramp grayscale contrast pattern). This concerns me because I want to have a professional calibration done, but I'm having my doubts if many calibrators are accurately setting contrast. I don't want to have any doubts before I drop $400 and permanently change my ISF preset settings. Could someone explain this to me?


I just want to express that I like a bright picture and calibration seems like it's going to make my TV look a bit washed out and foggy with the low contrast. I want to avoid this but I'm willing to understand or compromise if accuracy in gamma or color is compromised when using a nice bright contrast setting.

I am no calibrator but did pay the $400 to have my projector done. NOTE: projector is older 720p and only worth $450 max! Was it worth it, yes! is the contrast set correctly, you bet it is! When setting contrast and brightness they work together and where the numbers end up is not important and can not be used from set to set. Just for instance on my projector the contrast and brightness is set to -1. Hire someone from this board that had a good rep and you won't be sorry.
 

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You probably do want to see up to about 250 if at all possible, especially on an LCD when it's just about clipping.


As far as the back light setting, he was likely specifically target a light output of ~100cdm or 30-35fl (same amount of light, different units). A lot of LCDs can output 300 cdm or more, so having the setting at about 1/3 is totally normal.


I think what you are seeing here is the difference between what professional does, versus random forum members with a calibration disc.


But as to your impression of the picture, in a dark room 100cd/m should be fine, if you typically watch in a brightly lit enviroment, you should probably have a light output closer to 200cd/m or even 250cd/m. Just go a head and crank the backlight back up to 60-65 (assuming it's out of 100). I do that quite a bit, watching football sunday morning crank the backlight to 100, watching a movie at night back down to 42.
 

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Discussion Starter · #5 ·

Quote:
Originally Posted by sotti /forum/post/20866640


You probably do want to see up to about 250 if at all possible, especially on an LCD when it's just about clipping.

This is what I'm getting at. Video content is supposed to be 16-235. I read a very long thread on here regarding whether there is any intended content above 235 and the results were that it was likely encoding/compression errors and not real content. If a professional studio properly setup their monitors, then there shouldn't be any content above 235 visible when they are broadcasting or mastering in the studio.


My question then is, why are calibrators setting contrast to show content above 235 when it's only going to show content that wasn't meant to be shown? I am very confused on this and I don't want to drop $400 on a calibration until I have a very good explanation on why. Again, as I said before, is it because of trying to obtain accurate gamma or color? Without a good reason, then there is NO excuse for a professional calibration to be allowing a TV to show content above 235 and setting contrast so low as to give a washed out look. High contrast settings give lots of nice brightness and 'pop' which should be maintained if possible, not washed out.
 

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Point 1 -- Should you show above 235?

235 is not where content stops all the time. Live broadcasts including sports may have specular highlights in that range. Also the YCrCb to RGB transformations can create values above 235 in an individual RGB component. The legal values for Y at 16-235, but the values for Cr and Cb are 16-240, and you still aren't talking about the what happens when you feed them through the transformation matrix.


Also not all TV's handle clipping in the same fashion, so causing a TV to clip at any level can cause discoloration or make white point tracking difficult.


Most professional calibrators will go up over 235 whenever possible.


Point 2 -- Is the low contrast causing the washed out image

No, contrast isn't causing that. overall luminance maybe a cause of that, or it may be an accurate gamut compared to the oversaturated as shipped from the factory. It could even be the brightness control is too high, but contrast on an LCD doesn't wash out the image if it's too low. Most likely it is the overall luminance level, to correct simply turn up the backlight control.
 

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Quote:
Originally Posted by Timothy91 /forum/post/20866485


Hi all,


I have come accross threads and posts from many "pro" calibrations where the contrast setting is VERY low, even on my TV 55LH90 model. One person stated his contrast was at "81" which when I set my TV to 81, the contrast bars are visible up to the 250's. So, that has GOT to be wrong. Not only that but he quoted a backlight setting of "30" which again is ridiculously low. My question here is, would there be ANY situation with setting the gamma and color where a calibrator would be forced to drop the contrast that low? I have my doubts, but I'm no calibrator so, I would like to know what's up with calibrators setting TV contrast so low that they are FAR off on contrast accuracy (according to the standard reverse ramp grayscale contrast pattern). This concerns me because I want to have a professional calibration done, but I'm having my doubts if many calibrators are accurately setting contrast. I don't want to have any doubts before I drop $400 and permanently change my ISF preset settings. Could someone explain this to me?


I just want to express that I like a bright picture and calibration seems like it's going to make my TV look a bit washed out and foggy with the low contrast. I want to avoid this but I'm willing to understand or compromise if accuracy in gamma or color is compromised when using a nice bright contrast setting.

I am no professional calibrator but I leave super-white off on my PS3 and only show the flashing white bars below digital 235 on the various clipping patterns for white. On my new Samsung LCD TV, turning on super-white makes all the flashing bars very pinkish unless the contrast is lowered dramatically (since red drops sharply at digital 254/109% white). Leaving super-white off eliminates the pink discoloration and shows all detail below 235 properly even with contrast maxed.
 

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Quote:
Originally Posted by sotti /forum/post/20867566


Point 2 -- Is the low contrast causing the washed out image

No, contrast isn't causing that. overall luminance maybe a cause of that, or it may be an accurate gamut compared to the oversaturated as shipped from the factory. It could even be the brightness control is too high, but contrast on an LCD doesn't wash out the image if it's too low. Most likely it is the overall luminance level, to correct simply turn up the backlight control.

Well, on an LCD assuming brightness is set properly, the contrast control affects the contrast ratio of the TV. Backlight does not as it raises black level and white level proportionally. Setting contrast much lower to properly show whiter than white will then require a higher backlight setting to produce the target light output and this will result in a brighter MLL. So, lowering contrast excessively and then compensating by increasing backlight can wash out the image.
 

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Quote:
Originally Posted by PlasmaPZ80U /forum/post/20867605


Well, on an LCD assuming brightness is set properly, the contrast control affects the contrast ratio of the TV. Backlight does not as it raises black level and white level proportionally. Setting contrast much lower to properly show whiter than white will then require a higher backlight setting to produce the target light output and this will result in a brighter MLL. So, lowering contrast excessively and then compensating by increasing backlight can wash out the image.

Setting it to show up all the way up to 255, wouldn't cause it to be "washed out" unless you already had a horrible horrible contrast ratio. you are giving up at most 20% of your maximum light output so the total on/off contrast ratio is is only going to change in a similiar way. the difference between a set with 600:1 and 500:1 contrast is not signfigant. It's much more likely the room has a lot of ambient light so we are getting a flare off the screen that's dropping the ansi contrast below 100:1.


Turning up the backlight is the right solution, because small increase in black level compared to the ambient flare or the increased maximum light output will yield a much higher ansi contrast ratio.
 

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Quote:
Originally Posted by sotti /forum/post/20867634


Setting it to show up all the way up to 255, wouldn't cause it to be "washed out" unless you already had a horrible horrible contrast ratio. you are giving up at most 20% of your maximum light output so the total on/off contrast ratio is is only going to change in a similiar way. the difference between a set with 600:1 and 500:1 contrast is not signfigant. It's much more likely the room has a lot of ambient light so we are getting a flare off the screen that's dropping the ansi contrast below 100:1.


Turning up the backlight is the right solution, because small increase in black level compared to the ambient flare or the increased maximum light output will yield a much higher ansi contrast ratio.

It all depends on how much the lower the optimal contrast setting is for 255 vs. 235 on the given display. On my LN32D550 LCD, that difference is massive.
 

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Quote:
Originally Posted by Timothy91 /forum/post/20867409


is it because of trying to obtain accurate gamma or color?

If you're used to watching something like a typical cool color temperature (more blue than D65 gray), generally you will have to give up light output in order to get closer to a D65 gray on most displays. Some displays may have gamma fluctuations near where they clip near white, and generally displays do not tend to clip Red, Green, and Blue all at the same level, yet these items may be helped by lowering contrast and moving such irregularities above reference white. So, yes, it's possible that more accurate grayscale and gamma might require lowering light output from the absolute brightest image the display can produce.

Quote:
High contrast settings give lots of nice brightness and 'pop' which should be maintained if possible, not washed out.

Usually you have to give up a lot of light output in order to make most displays more accurate than the absolute brightest image they can produce. For anyone that doesn't consider calibrator prices insignificant, I highly recommend first trying more-accurate default settings many displays offer like THX, movie, or warm color temperatures. These sorts of settings will typically be closer to D65 gray than the default setting, and it will likely be more in the ballpark of a calibrated display compared to default settings. Considering the generally marginal performance of most consumer displays in dim rooms, personally I don't agree with statement that basically says "giving up... 20% of your maximum light output... is not significant", but certainly a number of displays will require giving up more than that sort of light output to get in the ballpark of D65 gray.
 

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Discussion Starter · #13 ·

Quote:
Originally Posted by alluringreality /forum/post/20867956


..I highly recommend first trying more-accurate default settings many displays offer like THX, movie, or warm color temperatures.

Ah. This is a complete dud by my testing. I put my TV on the THX mode and displayed all the test patterns available and it FAILED EVERY SINGLE TEST, EVERY TEST, EVERY TEST! Color, contrast, brightness, sharpness, etc, etc. THX simply wasn't correctly set, period, PERIOD!


So, don't try and even tell me that the THX preset is even "close" to accurate, it's NOT!


I have my TV set on 'warm' color temp. That's a given. No one should use any other setting.


My big problem is that people are saying it's fine to set a TV's contrast pattern to not clip content above 235. That why the hell have a contrast test pattern??? You say the contrast setting doesn't soften the picture, only change it's luminence? Bullsnot. Why not just crank the contrast to 0 and turn up your backlight to 100? It's just stupid talk you guys are spouting here. Unless you need to have contrast turned down to keep a major part of the picture to stay accurate, there is absolutely no reason to try and preserve noise and errors above 235, period. Turning contrast way down to show 250+ leaves the picture dull and soft looking. It's not accurate and any dolt off the street can take one look at it and say, dang, that doesn't look good.


I want my gamma, grayscale and color set correctly to match a professionally set monitor. I want my contrast not to show anything above 235, just like a professional monitor is set. To set it any other way is NOT professional (as a professional monitor shouldn't be showing anything above 235 in order to stay within the spec), so how can anyone call it a "professional calibration"? These are simple questions that should have precise answers from people in the business of professional calibration. If you aren't out to set my TV with the same standards of a professional studio display, then don't say you are doing a professional calibration.
 

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I do have some credentials. (see CalMAN)


I'm not saying your TV is setup properly, but cranking contrast till it clips at 235 can do as much harm as good.


Also with CRTs which have always been the reference, they don't hard clip anywhere, so they've always disclosed above 235. On CRTs contrast is the overall luminance. On LCD's contrast is the clipping point. The only reason they didn't get rid of the contrast control in the move LCD's would people would ask where it went.


Don't believe me, try one of the members who created the ATSC spec.
Poynton's Vector #1
Poynton's Vector #4


from #4:

" A home theatre calibrator, on assessing the greyscale response, will be savvy to this trick, and will adjust the display to

follow the gamma curve all the way up to peak."


Peak = 255 BTW


Don't believe Charles Poynton, well then just do whatever you like. You should be happy with your TV.
 

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Quote:
Originally Posted by PlasmaPZ80U /forum/post/20867580


On my new Samsung LCD TV, turning on super-white makes all the flashing bars very pinkish unless the contrast is lowered dramatically (since red drops sharply at digital 254/109% white). Leaving super-white off eliminates the pink discoloration and shows all detail below 235 properly even with contrast maxed.

Do you mean all the flashing bars down to 235, or all the flashing bars? Why would this setting be expected to affect below 235?
 

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Quote:
Originally Posted by Razz1 /forum/post/20868496


Do you mean all the flashing bars down to 235, or all the flashing bars? Why would this setting be expected to affect below 235?

When his display clips it clips red first, since the white point then shifts away from red, the unaffected D65 swatches below 235 appear pink because of the way your eye and brain perceive white(brightest white like color = white, everything else is relative). So he's saying that when he turns superwhite off and the PS3 actively hard clips above 235 his set no longer clips the higher stimulus signals, because it isn't receiving them and that 235 is still inside the whatever the clipping boundary is when contrast is at max.
 

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Quote:
Originally Posted by sotti /forum/post/20867566


Point 1 -- Should you show above 235?

235 is not where content stops all the time. Live broadcasts including sports may have specular highlights in that range. Also the YCrCb to RGB transformations can create values above 235 in an individual RGB component. The legal values for Y at 16-235, but the values for Cr and Cb are 16-240, and you still aren't talking about the what happens when you feed them through the transformation matrix.


Also not all TV's handle clipping in the same fashion, so causing a TV to clip at any level can cause discoloration or make white point tracking difficult.


Most professional calibrators will go up over 235 whenever possible.

I know of at least one LCD series that quits adjusting grey scale above 100% (235) ... no clipping involved. I suspect that the greyscale (10pt) controls on this set are working on the source values rather than the actual panel drive.
 

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Quote:
Originally Posted by HDTVChallenged /forum/post/20869062


I know of at least one LCD series that quits adjusting grey scale above 100% (235) ... no clipping involved. I suspect that the greyscale (10pt) controls on this set are working on the source values rather than the actual panel drive.

I'm not out in the field every day, so the particulars of any one set I may not be up on. I do know that every set including studio monitors, which I do have experience with, are compromises. Nothing is perfect, it's all about making the best compromises for the environment and requirements.
 

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Quote:
Originally Posted by Timothy91 /forum/post/20866485


Hi all,


I have come accross threads and posts from many "pro" calibrations where the contrast setting is VERY low, even on my TV 55LH90 model. One person stated his contrast was at "81" which when I set my TV to 81, the contrast bars are visible up to the 250's. So, that has GOT to be wrong. Not only that but he quoted a backlight setting of "30" which again is ridiculously low. My question here is, would there be ANY situation with setting the gamma and color where a calibrator would be forced to drop the contrast that low? I have my doubts, but I'm no calibrator so, I would like to know what's up with calibrators setting TV contrast so low that they are FAR off on contrast accuracy (according to the standard reverse ramp grayscale contrast pattern). This concerns me because I want to have a professional calibration done, but I'm having my doubts if many calibrators are accurately setting contrast. I don't want to have any doubts before I drop $400 and permanently change my ISF preset settings. Could someone explain this to me?


I just want to express that I like a bright picture and calibration seems like it's going to make my TV look a bit washed out and foggy with the low contrast. I want to avoid this but I'm willing to understand or compromise if accuracy in gamma or color is compromised when using a nice bright contrast setting.

You need to send the set a 16-235 video level signal for that pattern to work right. If you send it RGB levels, or Super-white video levels, then gray bars will flash way into the 250s, and 234 will never clip. This will render the pattern useless.


If the set is fed video levels, then perhaps the setting of "81" was in fact justified to prevent clipping.


I would say if he/she was in fact sending 16-235 video levels, he would most likely be able to clip 234 when maxing everything out.



Most people having this problem with that test pattern are displaying "super white video levels" or "RGB" Video levels. I have only found the pattern useful when sending a 16-235 signal, clipping everything below and above. You have to ensure the background white is displayed at 235.
 
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