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Author Topic: LCD monitor calibration - which brightness?  (Read 26571 times)

deelight

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LCD monitor calibration - which brightness?
« on: March 07, 2007, 08:20:17 am »

Dear all!

I frequently visit this forum and quite often read about colour management and monitor calibration.

As my new monitor (NEC 2690, 400cd/m2 Max.) will arrive today I think about what will be the best setting for calibration and profiling (I use basiccolor SQUID)?

There are diverse threads about this topic, but no conclusion about the correct setting is possible. I would like to ask you guys, what you did and why: which brightness???

Any colour management professionals on this thread who exactly know what setting will be the correct one? Why?

Also very interesting question: do you use Gamma 1,8 or 2,2 (I am on MAC) or L*? Why? As far as I know L* is a linear response of the monitor on the linear grey scale (and the correct setting for LCD) and Gamma is for CRT monitors.

Thanks in advance!

Best,

Clem
« Last Edit: March 07, 2007, 08:34:22 am by deelight »
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photopat

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LCD monitor calibration - which brightness?
« Reply #1 on: March 07, 2007, 09:46:13 am »

There is no universal "right setting when it comes to setting the brigthnes of a monitor.
it depends on your working envirenment.

If you work in a cave like envirement ( like I do) 100 cd/m2 is about right for me, but if your work envirement is alot brighter then you need to set a higher brigthness value.

As for gamma. Most monitors have a native gamma  close to gamma 2.2  ( 2,3-2,5 I think )  and the less you have to adjust the screen the better result you will get ( same with whitepoint where most monitors are close to 6500k)

Gamma 1,8 for Mac is a old thing and nothing to be bother with these days.

So  with a whitepoint of 6500k  and gamma 2,2  ( or D65 ) is right in most cases.
Brigthness you 'll have to set according to your working envirenment.

Patrick
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deelight

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LCD monitor calibration - which brightness?
« Reply #2 on: March 07, 2007, 11:00:40 am »

Patrick, thanks!

Yes, of course the brightness may depend on the surrounding conditions but OTOH I read that some people suggest not to set it brighter than 120 cd/m2 because prints might come out darker than on screen even though the monitor is profiled.

In fact I always set my actual LCD monitor to Max./L* and printed a very dark BW yesterday and it was probably 2/3 f-stop darker than displayed. All devices are properly profiled. I also work in a quite dark environment.

That made me think again about the brightness settings.

@All: Thanks for more opinions!

Clem
« Last Edit: March 07, 2007, 03:58:28 pm by deelight »
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61Dynamic

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LCD monitor calibration - which brightness?
« Reply #3 on: March 07, 2007, 01:14:55 pm »

Quote
There is no universal "right setting when it comes to setting the brigthnes of a monitor.
it depends on your working envirenment.

If you work in a cave like envirement ( like I do) 100 cd/m2 is about right for me, but if your work envirement is alot brighter then you need to set a higher brigthness value.

As for gamma. Most monitors have a native gamma  close to gamma 2.2  ( 2,3-2,5 I think )  and the less you have to adjust the screen the better result you will get ( same with whitepoint where most monitors are close to 6500k)

Gamma 1,8 for Mac is a old thing and nothing to be bother with these days.

So  with a whitepoint of 6500k  and gamma 2,2  ( or D65 ) is right in most cases.
Brigthness you 'll have to set according to your working envirenment.

Patrick
[a href=\"index.php?act=findpost&pid=105230\"][{POST_SNAPBACK}][/a]

Monitor brightness & Working Environment:

There is a correct luminance for viewing and for the display. Your monitor, if too bright, can cause eye strain and effect your ability to perceive correct white levels--regardless of the overall brightness of your working environment. Anything above 140cd/m2 can cause these problems in my experience (as you pointed out Clem).

120cdm/2 is the ideal brightness as it is an optimal compromise between good contrast (white-point) and brightness (black-point) for LCDs.

Your working environment is recommended to be dim at around 32 lux (think the Bat Cave) however levels of 64 lux are acceptable in order to avoid depression.  The more ambient light there is in an environment, the greater issue there is with glare. Particularly of your own mug being reflected off the screen.

Gamma:

Gamma is determined by the video card, not the monitor.

Macs used to be gamma 1.8 however that does not seem to be the case anymore. If I calibrate my ACD to native gamma it produces results that are near identical to 2.2 (My computer is a Dual 2.3 G5 with a Radeon 9650). My brother's Macbook (Intel video card) does the same.

It is best to calibrate gamma to either "Native" or L* as that will not adjust the video card LUTs prior to profiling.

Attached is a summary table of ISO 3664 and 12646 that lays out recommended settings. The image came from a Creative Pro article on the subject of the digital darkroom, but I've lost the link.
« Last Edit: March 07, 2007, 01:18:23 pm by 61Dynamic »
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deelight

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LCD monitor calibration - which brightness?
« Reply #4 on: March 08, 2007, 12:41:52 pm »

Quote
Gamma:

Gamma is determined by the video card, not the monitor.

Macs used to be gamma 1.8 however that does not seem to be the case anymore. If I calibrate my ACD to native gamma it produces results that are near identical to 2.2 (My computer is a Dual 2.3 G5 with a Radeon 9650). My brother's Macbook (Intel video card) does the same.

It is best to calibrate gamma to either "Native" or L* as that will not adjust the video card LUTs prior to profiling.

[a href=\"index.php?act=findpost&pid=105284\"][{POST_SNAPBACK}][/a]


Hello Daniel!

Thanks, that confirms what I was thinking but not exactly knowing.

Now, after receiving the monitor and doing the first steps very quickly new questions arised.

On my old LCD monitors (iMac G5) I did not have hardware settings like:

black point
contrast
sharpening

Where to set them? Leave them at factory presets?

My basiccolor software (used with SQUID2) recommends to set the luminance to L* and I set the monitor color to native temperature.

This is what I did, but what to do with the other settings?

Aswell I tried to set the brightness and contrast to 50% and calibrate to 120cd/m2, but after calibration the software informed me that the monitor now is calibrated to 276 cd/m2. I suppose, the hardware setting must simply be lower than 50% because the software is only able to cover a certain area via the computers graphic card, right?

Thank you all!

Clem
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61Dynamic

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LCD monitor calibration - which brightness?
« Reply #5 on: March 08, 2007, 01:46:57 pm »

Calibration is the process of tweaking the analog hardware itself to conform to a set standard prior to profiling. The only analog element that can be adjusted on an LCD is the backlight brightness (which adjusts black point and white point simultaneously). The other controls are software adjustments and will adjust the LUTs reducing color reproduction.

Set the display to the factory defaults and then during calibration only adjust the brightness until it reads 120. That will net you the best results.
« Last Edit: March 08, 2007, 01:47:55 pm by 61Dynamic »
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jackbingham

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LCD monitor calibration - which brightness?
« Reply #6 on: March 10, 2007, 03:59:45 pm »

There are plenty of LCD monitors that respond well to color adjustments being made in the hardware even if they are not ddc. I would not make a blanket statement it's good or bad for all.
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61Dynamic

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LCD monitor calibration - which brightness?
« Reply #7 on: March 10, 2007, 06:28:51 pm »

Quote
There are plenty of LCD monitors that respond well to color adjustments being made in the hardware even if they are not ddc. I would not make a blanket statement it's good or bad for all.
[a href=\"index.php?act=findpost&pid=105911\"][{POST_SNAPBACK}][/a]
True, there are displays with 10bpc LUTs (or more) but they are interpolating the 8bpc signal from the video card to minimize the effect of making adjustments when it may be needed. Even so, it is best not to fiddle with the controls unless you have to. Monitors that support 10bpc LUTs generally higher-end and don't usually need to have their LUTs adjusted anyway unless you need a different gamma or temperature than what's native. Most of us photographers don't need that.

So yeah, what I said a couple posts back is a blanket statement, but 98% of the time it's the right statement--for our world. If someone falls in that remaining 2% then they already know they need something other than the typical calibration and would say so.

(and it should be clarified that the adjustments outside of brightness are not done in hardware. They are software, even if done on the monitors controls)
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Tim Lookingbill

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LCD monitor calibration - which brightness?
« Reply #8 on: March 10, 2007, 09:53:54 pm »

"...(and it should be clarified that the adjustments outside of brightness are not done in hardware. They are software, even if done on the monitors controls)..."

I keep reading this but I can't figure out how this happens or how to prove it's happening. What if I attach the display to a Mac that doesn't have software for it? What is being adjusted in the OSD, then?

Not doubting you, 61Dynamic, but I keep asking this question and no one ever seems to have an answer.
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61Dynamic

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LCD monitor calibration - which brightness?
« Reply #9 on: March 11, 2007, 01:32:13 pm »

Quote
"...(and it should be clarified that the adjustments outside of brightness are not done in hardware. They are software, even if done on the monitors controls)..."

I keep reading this but I can't figure out how this happens or how to prove it's happening. What if I attach the display to a Mac that doesn't have software for it? What is being adjusted in the OSD, then?

Not doubting you, 61Dynamic, but I keep asking this question and no one ever seems to have an answer.
[{POST_SNAPBACK}][/a]

It doesn't matter what the display is attached to. When you adjust the OSD controls, you reduce the number of brightness levels the display can render for each channel. Brightness is the only thing that is analog as that is controlling the brightness of the backlight. The adjustments--other than brightness--are done on the LCD screen itself which is controlled by the software in the display.

For example, lets say you want to reduce the red channel on an LCD. You change the Red value from its default of 100 to 80. That change reduced the number of brightness levels of the red LCDs crystals by 20%. So instead of having 256 different levels that the crystal will twist to, it now only has about 204 levels of adjustment available. The last 52 levels of adjustment are no longer available to it. This will have an adverse effect on color rendition as a whole since the reds are mixed with green and blue crystals to create the color of the final image.

Andrew Rodney has a [a href=\"http://digitaldog.net/tips/]tutorial[/url] on testing the monitor profile which you can use to prove this effect. Look to the bottom-right for the PDF.

On the topic of display bit depth, even 12bpc or 14bpc displays are only outputting to a 8bpc LCD screen. They simply have hardware that intercepts the 8bpc image from the computer, interpolates it to 10/14bpc, makes adjustments and then outputs it back to 8bpc for rendering on the screen. At this current time, there is no such thing as a LCD screen that is higher than 8bpc on the market. NEC has a prototype of a 10bpc screen from what I've read so it is something that is our future (along with support for it in the video card, connection standard, and operating system which are also required to take full advantage of high-bit-depth screens). But until then only adjusting the brightness will net the most accurate calibration and profiling results.
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jackbingham

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LCD monitor calibration - which brightness?
« Reply #10 on: March 11, 2007, 02:24:38 pm »

I'm sorry but you're way off the mark here. Monitors that have 10 bit plus internal luts provide a great deal of adjustment and there are countless examples of this on the market. NEC, Eizo, LaCie are just a few. Just because the signal coming in is 8 bit doesn't mean you can not benefit from tayloring the data handling in the display before hand. With a tonal range per channel of 1024+ you can certainly adjust how the display interprets the 8 bits coming in with a fair amount of flexibility. You are not loosing one bit of valuable data. LCDs are being used more and more in the prepress environment at d50 with amazing accuracy and no banding or data loss. All that color adjustment is being done in the monitor lut to alter it's color handling in front of the 8 bit incoming data.
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digitaldog

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LCD monitor calibration - which brightness?
« Reply #11 on: March 11, 2007, 02:31:54 pm »

Quote
On the topic of display bit depth, even 12bpc or 14bpc displays are only outputting to a 8bpc LCD screen.

Yup. The OS and the applications all have to be updated to get close to a true, high bit editing workflow. Higher bits in the display is mildly useful but we'd be far better off with better display technology that allows physical control over the device behavior like we had with 20th century CRT displays. This high bit stuff is far more useful for those marketing hardware and software to deal with calibration than anything else! CCFL technology is piss poor really compared to what's coming down the pike (LED is a good start).
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Nill Toulme

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LCD monitor calibration - which brightness?
« Reply #12 on: March 11, 2007, 07:32:24 pm »

Clem I strongly recommend that you get the NEC Spectraview II software for your 2690.  I don't think it's been updated to support that monitor yet, but if not it will be soon, and it's excellent.  It does everything for you on a one-button, turnkey basis.  Set your parameters to D65, 2.2, 120 cd/mē (or so), hit go and just walk away.  It calibrates the monitor directly via its internal 12-bit LUTs, produces a profile, sets it to the default, and you're done.  I can't imagine how it could be any better or any easier.

I have the 2090 and initially set it to 120 cd/mē but found that a little too bright in my own "cavelike environment."  I now set it to 100 cd/mē.

Nill
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imagingassociates

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LCD monitor calibration - which brightness?
« Reply #13 on: March 16, 2007, 12:58:57 am »

More information about Monitor Calibration and Color Management can be found using these targeted swicki search engines:

Monitor Calibration Tips Search Engine
Color Management Search Engine
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