HD Monitoring Again!

[Toke]

[Graeme Nattress] “Surely though, in 8bit video, the brightest bit is only 256 times brighter than the darkest?”

That’s why we use non-linear gamma, right?

THG measurements (black level, contrast):
Dell 2001FP 0.62 258:1
LaCie 321 / NEC 2180UX 0.3 500:1
Dell 2405FPW 0.3 833:1
Apple Cinema 0.66 439:1
Eizo L997 0.4 575:1
ViewSonic VP231WB 0.42 338:1
NEC 2180WG-LED 0.29 448:1

So the black levels are getting lower, but we are still far away from hq, witch would be <.1. That last NEC lumiled had a perfect color representation. And what will be the price for lumiled-hd? Near ecinemasys?

[Graeme Nattress]

I can’t quite visualise how non-linear gamma relates to contrast ratios though….. Video is non-linear (about 0.4) for two reasons, to distribute more bits to the darker values so as to reduce banding, and hence not need 12bits just so that we don’t see artifacts, and to counter the 2.5 gamma of a CRT. But in any gamma 0=0 and 1=1 – those values don’t change, just how the values inbetween get distributed. Thoughts?

Graeme

– http://www.nattress.com – Film Effects and Standards Conversion for FCP

[Toke]

I see no problem using monitor with 1000:1 contrast ratio with 8bit colors.
Let’s assume that black level (0,0,0) is 0.1 cd/m^2 and white level (255,255,255)then 100 cd/m^2.
With linear gamma rgb values would give intensity:
(1,1,1) 4.0 cd/m^2
(2,2,2) 7.9 cd/m^2
(3,3,3) 11.8 cd/m^2
etc.

With gamma of 0.4:
(1,1,1) 1,8 cd/m^2
(2,2,2) 2,4 cd/m^2
(3,3,3) 2,8 cd/m^2
etc.

[Graeme Nattress]

Toke, I hope you don’t mind me sharing some thoughts here to try and get to the bottom of this, as it all leaves me confused some what.

In light terms, contrast ratio is white / black, which in your 100 / 0.1 case gives a 1000:1 contrast ratio. This makes sense so far.

But in digital terms, you’d get white / black, which is 255 / 0 = infinte. So something’s not quite right there.

In audio, dynamic range is peak signal / noise (or distortion) floor in db, which for an 8bit system is what, about 48db? (16 bit being about 96db, give or take)? But if I play a 8bit recording on a 16bit CD player, I’ll only hear 8bits worth of dynamic range, even though the player is capable of more (although I’d have to be in a dead silent room playing the music really loud to hear 96db dynamic range).

Is not the light situation similarly limited by the noise floor of the signal feeding the monitor?

Graeme

– http://www.nattress.com – Film Effects and Standards Conversion for FCP

[Toke]

I don’t mind at all, thinking of these makes me to refresh my memory and logics also.

Amount of color bits restricts the number of tones you can have, but not how big contrast ratio you can have between the ends.
Only if you use linear gamma and want to reproduce a shot excactly how it was in real life, then (4,4,4) has to be twice as bright as (2,2,2,) etc.

You can adjust your display to show 10 f-stops with 8bits, there just is less tones per f-stop.
And usually in moving images, you want pictures look good rather than naturally realistic.

More you boost your contrast ratio, easier tone banding appears.
Gamma helps in this, because you can put more of tones in critical area and less elsewhere.
To show 2.2-gamma 8bit tones you need 12bits in linear gamma.

As to analogy with audio, with 8bit audio you can’t reproduce a sound that is weaker than -48dB but you can adjust the 0dB point.
With 8bit color you can’t reproduce a tone that has half the brightness of (1,1,1), but you can adjust the brightness of (1,1,1).

And to get back to real life, lcds have had an annoyingly high black level, but very high white level. So talking about contrast ratios doesn’t really tell if the picture will look good. Contrast can be high, but that doesn’t help if black level is also high. At least if you are planning to watch the display in traditionally dim lit room.

I’m not sure if there is any kind of standardization to contrast ratio in any color spaces, I’ve understood that they only specify the relation of tones to each other, not the overall output.

Maybe Apple has some ideas about everybody looking the same picture, because their displays don’t have adjustable contrast. Most of the rest of the world does have…

[Graeme Nattress]

“Contrast” on a CRT is white level, and “brightness” on a CRT is black level?? The brightness control on an Apple monitor adjusts the white level does it not?? Given that the black level is fixed by nature of the LCD, I don’t think you could adjust that.

So, contrast range in a monitor is much more like max volume level in audio, because the black level is fixed, but you can scale the white point to anywhere you want given the bounds of seeing banding, and how much light you want to put out. Given that LCDs are bright enough, we have to tackle black level. Personally, in a lighted room, I have no issues with LCD black level – it’s only in darkness do I have a problem, and then, in real world images, it’s minor.

Graeme

– http://www.nattress.com – Film Effects and Standards Conversion for FCP

[Toke]

Sadly brightness adjustments also affects the black level in lcds.
Maybe that’s because backlight brightness is also used to handle overall brightness?

[Graeme Nattress]

In an LCD, black level and white level are tied by the backlight and the LCD itself. As you make the screen brighter (white level) you’re also going to allow through more black level too.

Graeme

– http://www.nattress.com – Film Effects and Standards Conversion for FCP

[David Battistella]

This sharp monitor is the largest true 1920×1080 monitor on the market, but it doesn’t do 23.98 frame rates. you need a 1500$ miranda converter to do the pulldown on the fly, but it looks unbelievable.

David

https://www.sharpusa.com/products/ModelLanding/0,1058,1592,00.html

between 7-8k cdn right now

[Toke]

Does it accept 1080p input?