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Author Topic: Monitor Calibration - Colour Space  (Read 656 times)

Chris_Stuart

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Monitor Calibration - Colour Space
« on: March 25, 2017, 06:17:44 AM »

Can someone please clarify appropriate gamut setting (colour space) to use when calibrating a monitor for image processing.
I have read various books and I have searched high and low on the internet, but can find no clear answer or explanation to this.
Much available information is from several years ago and may not be so relevant today as things digital move so fast.

I have recently purchased an EIZO CG277 monitor and am now seeking to get the best out if it.
In LightRoom and Photoshop I have set my preferences to ProPhoto RGB gamma 1.8.
These seem to be fairly universally agreed settings.

But monitor settings are less clear.
In particular the first choice when calibrating the monitor is to set the gamut.
There are numerous options available but the most likely options appear to be:-

Monitor Native
Adobe 1998
ProPhoto RGB

None of the articles on monitor calibration advise on colour space.
They all discuss gamma and brightness.
Gamma seems to be generally agreed now at 2.2 for monitors, and brightness seems to be down to personal choice and what you need for output, such as choice of paper for printing.

But what about colour space?

And if processing in ProPhoto RGB colour space - would it make sense to also calibrate the monitor to this?
And if so, can anybody clarify, if ProPhoto RGB should be set to gamma 1.8 in LR and PS, why would it be different for the monitor?

All clarification greatly appreciated.

Many thanks

Chris
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TonyW

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Re: Monitor Calibration - Colour Space
« Reply #1 on: March 25, 2017, 07:50:49 AM »

I think it would help your understanding having a look at good reference sources such as the books by Bruce Fraser, Jeff Schewe and Andrew Rodney. 

I also think there may be a little confusion created by what you have seen so far. 

Hoping not to add to the confusion or worse offering poor advice, my view on what you have said so far:

  • Your working/editing spaces choices are usually one of these -sRGB,  Adobe RGB or ProPhoto within Photoshop.  Lightroom uses its own working space internally based I believe on a modified version of ProPhoto (Mellisa?) with a gamma of 1.0.  AFAIK you cannot change this but you can elect to output with whatever profile space LR provides in the output menu
  • Your monitor native gamut can achieve around 99% of Adobe RGB colour space and AFAIK there are no monitors that can cover ProPhoto gamut and maybe we will never see such.
  • While your monitor may have options to limit/mimic an sRGB or Adobe RGB device (within its limits) you cannot really calibrate to these colour spaces, rather you set calibration to known standards D65, Gamma 2.2 and monitor brightness to suit editing environment e.g. 100 - 150 cd/m2 (just an example real values may vary more)
  • What you are aiming for in display calibration is what you have already mentioned i.e. the White Point and the Gamma of the display.  This gives colour savvy applications like Photoshop the necessary information about the display condition to allow a correct image preview.

Some information that may be of help with hardware calibration of your Eizo
https://www.youtube.com/watch?v=Hh7cQTjhL0M
https://www.youtube.com/watch?v=LWUBNwSyhxg
« Last Edit: March 25, 2017, 07:56:21 AM by TonyW »
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scyth

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Re: Monitor Calibration - Colour Space
« Reply #2 on: March 25, 2017, 10:40:41 AM »

But monitor settings are less clear.

the first question is, what is your goal - do you print or you just do conversion/post-processing for yourself/to post on "web" ? your calibration settings ( white point/"temperature", curve/gamma, intensity/brightness & contrast/or black level/, gamut) depend on that goal... for example if you work to post on web you certainly want to have gamut calibrated to "sRGB" to make things easier
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Chris_Stuart

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Re: Monitor Calibration - Colour Space
« Reply #3 on: March 25, 2017, 12:22:59 PM »

Thank you TonyW and Scyth for your replies.

I have read Jeff Shewe's books The Digital Print and The Digital Negative but I am not familiar with books by Bruce Fraser and Andrew Rodney so will look into those. I have also seen the YouTube videos your referred me to, Tony, thanks for the links.
For the benefit of anybody else who stumbles upon these posts there is also a useful YouTube video by Victor Aberdeen of Eizo at
https://youtu.be/I-ZQKYuds_Q - but even that does not answer my question.
There is also some useful video and information on website of Josh Halko, Australian wildlife and nature photographer.

My primary goal is preparing images for print.
But I also post images to the web I used to just do web sharpening and convert to sRGB for that but guess I may need to start soft proofing for web as well as for print - and perhaps sRGB, which is a Gamut option, might be useful for that purpose.

I was using an iMac and getting reasonable results, but the iMac is elderly and it will no longer let me upgrade the OS and is now struggling with LR and PS, so I have hooked a fairly up to date Macbook Pro to the Eizo monitor and hope to get more accurate and consistent prints.

For the moment I have set the monitor to Gamut Adobe RGB 1998 with settings of D65 and Gamma 2.2 on the basis that this will not be "incorrect"
But I would like to understand better what the other gamut options will do. Guess it may be simply, as you say TonyW, that the monitor will just mimic a particular colour space. In which case maybe the option of ProPhoto RGB might be worth trying, given that LR uses something akin to this and it is what PS is set to use.

Thanks again
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Royce Howland

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Re: Monitor Calibration - Colour Space
« Reply #4 on: March 25, 2017, 12:55:55 PM »

If your primary target is preparing images for print, I'd say set up one calibration preset with monitor native gamut. The objective of doing this is so that the full range of colours that the monitor can produce will be available to you to see as you edit your images. Monitors that claim a near-Adobe RGB gamut may lead you to believe that Adobe RGB is an appropriate calibration choice, but if you wish to get the full value of the monitor's native performance I'd say this isn't the best choice. That's because the display panel in fact will almost certainly fall short of Adobe RGB is some areas, and actually exceed it in others.

The whole point of colour management in my opinion is to correctly characterize the colour performance of a given device, and allow the full range of colour reproduction potential of that device to be consistently and appropriately realized when moving image data between devices. If you constrain a device to an artificial colour space, that's needlessly leaving part of its performance envelope on the cutting room floor.

sRGB for the web is a special case. If you care about it, you can set up another calibration preset and switch the monitor to it if you want to and use it to review images that you're prepping for the web. Personally I don't do this for several reasons. First, I also target print and frankly don't really care a whole lot what my images look like when they're not in my chosen presentation format. Second, most monitors that claim to be roughly sRGB class devices don't in fact exactly cover sRGB (just as most near-Adobe RGB devices don't excatly cover Adobe RGB). So viewing an image in sRGB is not an accurate representation of how the image will look on a device that isn't in fact an sRGB device. Finally, by far the vast majority of sRGB devices out there will not be calibrated in any sense at all. So using a colour managed workflow to preview images with great accuracy in a simulated sRGB environment, and then throwing them out in a seething sea of colour chaos seems to me like going for 10 decimal digits of precision on a numerical value with error bars +/- 50%. It's just not a worthwhile enough exercise for me to spend any time on it.

In terms of ProPhoto RGB, I'd say there's no point attempting to calibrate a monitor to this colour space even if software would let you attempt it. (And I'd be surprised if it would let you make that attempt, but I'm not familiar with Eizo's calibration software.) That's because ProPhoto RGB is so drastically beyond the gamut of any monitor that I's say it's pretty useless to attempt to characterize the colour reproduction of a monitor with reference to ProPhoto RGB. Using monitor native gamut should give you the maximum colour reproduction range the monitor is capable of... there's no reason I can think of to try using a wildly over-shot synthetic colour space as a reference for the monitor calibration run.

Where ProPhoto RGB makes sense is as a working space with your editing software, because it's large enough to contain image data that must be shipped amongst a range of devices (cameras, scanners, monitors, printers, etc.) that have a very large variation in colour gamuts. These gamuts are non-overlapping with each other in a lot of areas of the colour range, and they also can exceed Adobe RGB in a number of relevant areas of the gamut. (Of course this is dependent on the subject matter you photograph, and the actual colours found in the images you capture, edit and print.)

You do have to be more careful with your editing when using ProPhoto RGB, since it exceeds what your monitor is capable of displaying and therefore you may unintentionally push the image colour in ways that "cook" it without realizing that's what you've done. For this reason, a lot of folks choose Adobe RGB as their default, go-to working colour space. Adobe RGB is a relatively close to many modern monitors' native gamuts, and it covers a very large range of real-world colours that you want to carry from capture to print. But there are real-world colours that you can carry from capture to print that fall outside Adobe RGB, so for those there is ProPhoto RGB.

Side note: colour spaces like sRGB, Adobe RGB and ProPhoto RGB are synthetic colour spaces. They are artificially created for purposes primarily to do with processing in various intermediate stages of imaging workflow. Camera profiles, monitor profiles, scanner profiles and printer profiles all contain device-specific colour spaces. They are created primarily to characterize the specific colour reproduction of an actual device (or at least a class of very similar devices that can be expected to behave very much like each other). Device-specific colour spaces have the primary purposes of allowing the imaging workflow to render image data into or out of the device in a consistent & appropriate way. Mixing up the purpose & use of synthetic and device-specific colour spaces is rarely something you'd want to do on purpose. In some cases, the negative consequences can be fairly minimal, e.g. calibrating a near-Adobe RGB monitor to Adobe RGB instead of the monitor native gamut; still, in most cases I'd say there's no upside to using a synthetic colour space to constrain the colour reproduction range of an actual device, when calibrating that device.

That's my take on it...

scyth

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Re: Monitor Calibration - Colour Space
« Reply #5 on: March 25, 2017, 02:15:11 PM »

Camera profiles, monitor profiles, scanner profiles and printer profiles all contain device-specific colour spaces.

a "camera profile" for an input device like a digital camera does not contain any definitions of any device specific color space at all, "camera profile" simply contains some data that raw converter uses to convert from camera's digital numbers (and those are absolutely not any coordinates in any proper color space of any kind, more so that operation happens after various normalization/linearization/demosaicking and whatever other raw-converter specific stages like pre/post demosaicking WB, NR/shapening/optics corrections/etc) to a some (whatever raw converter/camera profile author/s/ decided and how they decided) proper color space / __NOT__ device specific /...
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TonyW

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Re: Monitor Calibration - Colour Space
« Reply #6 on: March 25, 2017, 03:07:34 PM »

...My primary goal is preparing images for print.

...For the moment I have set the monitor to Gamut Adobe RGB 1998 with settings of D65 and Gamma 2.2 on the basis that this will not be "incorrect"...
Ideally as your goal is preparing images for print you should make a monitor profile to match your print material i.e. monitor white  point should match paper white point.

Your monitor is NOT an Adobe RGB device it is its own device and has its own colour gamut which in this case is said to cover around 99% of Adobe RGB gamut.  You cannot calibrate to Adobe RGB, or for that matter ProPhoto. 

The menu may show you choices but this is only for emulation within monitor limitations of course and as such ProPhoto is a nonsense as the monitor cannot cover a fraction of that space. So unless you have good reason setting the software to less than Native gamut is not the best idea

Although my system different in that I use an i1 Display the recommended settings are a good starting point.  Maybe this will be of help

1 Define and Create a new target

Anything less than Monitor Native are emulations and unless you are trying to simulate another device the recommended Monitor Native choice should probably be used

2  Select monitor Brightness and White Point - in this case 110cd/m2 (your value may be very different) and D65.


3.  Select Black level.  Leave as suggested minimum


4.  Set Tone Curve (Gamma)  Use rec. settings


5. Give the profile a name and go to next.  You will end up with a screen similar to this displaying your profile choices. 

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Doug Gray

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Re: Monitor Calibration - Colour Space
« Reply #7 on: March 25, 2017, 04:40:07 PM »

Ideally as your goal is preparing images for print you should make a monitor profile to match your print material i.e. monitor white  point should match paper white point.

Nice writeup. The only place I differ is in setting the white point to the paper white. But you're in good company. Andrew Rodney also recommends doing it that way and it's not wrong.

My preferred setup is to set the white point and luminance to a "perfect" white illuminated by the hard proof viewing system. Then, when soft proofing with "show paper white" the brightness and paper tint and will be adjusted to match what the actual paper looks like in the hard proofing station. Typically, somewhat bluer and dimmer but it varies quite a bit from one paper to another. Since the paper's profile has this information it can correct and display the image to match the paper. The big advantage is that you don't have to have a bunch of different monitor settings that you have to switch to when you print on different papers. It's all handled in the soft proofing.

To make a monitor profile match a viewing station you set the luminance and tint (xy coordinates) using an all white image but soft proofing it using a profile from the same printer/paper that you also put in the hard proof viewing stand. Adjust to match. Then you are good for other papers with differing brightness and tint.  The only remaining variable is uV.  If your viewing stand has little or no uV then use profiles with uV cut (M2). If you have a modern one that simulates the full D50 (including uV) then use a profile generated under M1.

But there is a downside. Soft proofing decreases the monitor luminance to match the degree that a paper is less than a perfect white. This shift is very noticeable and unsettling. It's sometimes called the "make my image look bad" checkbox.  But it is entirely psychological because the default editing monitor mode is to assume a 100%, perfectly reflective paper white and such papers don't exist. Print paper is typically only 85% to 90% reflective.

But if you set things up this way you will get good soft proofing with different media and not have to remember to change the monitor settings nor will you have to go through the tedious process to create then for all the different papers you have.

However, some find the luminance drop distressing enough they prefer to have multiple monitor profiles.  Both approaches are perfectly fine.
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Chris_Stuart

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Re: Monitor Calibration - Colour Space
« Reply #8 on: March 26, 2017, 02:20:11 PM »

Many thanks to everybody who has responded, and in such detailed and most helpful ways, including screen shots.

The conclusion I come to from this is to set the Monitor Gamut to Native.

After that my settings can remain pretty much as they are for the moment, but may need tweaking (in particular brightness) once I start doing some prints.

Thanks again
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pfigen

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Re: Monitor Calibration - Colour Space
« Reply #9 on: March 27, 2017, 02:12:53 AM »

Don't forget when you get to the screen that has the Advanced option to click on that and UNCHECK the Reflect Tone Curve in Blacks option, or you'll get black point compensation to your screen, not such a great thing. Also, choosing Minimum for your black point may leave you with blacks that are actually too dark. For a fairly dim room I use .4 for the black point and it's just about the right feel for blackness.
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