Monitor Calibration and Colour Space - Particularly for those from the film world.

[Steven Lee]

@Alan Edward Klein Can I try? I will try not to use jargon too much.

When you calibrate your monitor, you are adjusting its output to a known standard (sRGB, AdobeRGB, DCI-P3, etc). They are also called "color spaces". But hardware always has limitations, this is why monitor specs can say "98% of AdobeRGB", for example. sRGB is the smallest colorspace that most monitors can actually display, that's why it's popular.

Then you have your photo. It is just a bunch of RGB values for every pixel. These values are coordinates in a 3-dimenstional color space, and can be only interpreted correctly if the color space is known. So a color space profile can be added to a JPEG file. If it's missing, most systems will assume sRGB.

What happens if you want to display an sRGB image on a calibrated AdobeRGB monitor? This is where color management kicks in. All modern operating systems and applications are color managed. This means that they will do the mapping of sRGB values into AdobeRGB automatically. AdobeRGB is a superset of sRGB, so every sRGB pixel will be shown correctly.

What happens if you want to display an AdobeRGB image on a calibrated AdobeRGB monitor? Well, obviously you will see the correct color.

But what happens if an AdobeRGB image is shown on a sRGB monitor? In this case some values will have to be clipped, because AdobeRGB is wider than sRGB. You can simulate this effect with "Color proofing" feature in most editors.

This is why it makes sense to:

• Calibrate your monitor to the widest gamut it supports, because it will allow you to see all images with smaller-or-equal color spaces without clipping.
• Use sRGB for your images if you want them to be shown correctly on everybody's monitor.
• Use a wider color space in your images for long term storage, because monitors of the future will likely support wider and wider color gamut.

 

[Mr Bill]

My head is starting to hurt. Now I'm really confused. Please keep it simple for this old man.

Hi, sorry, but the inner workings of the thing are just not simple. Now, the actual USAGE can be fairly simple; it can be turned into a series of rules to be followed, and the results can be surprisingly good.

I use a monitor calibrated to sRGB to edit my photos (scanned film or digital photos) and video clips. I use sRGB because I heard that the web mainly uses that. I use my eyes to get colors that are acceptable to me.
...

So here are my questions:

1. Will other viewers who have calibrated their monitor to sRGB "see" the same colors that I see in my photo?

I can't really answer; I'm not sure what you're doing because you're not using the right words. When you say "calibrated to sRGB" I just don't know, for sure, what you mean.

You might as well tell me that you took some photos with a "calibrated camera system" and ask if the exposures will be ok... I just wouldn't know what you actually did. Now, if you were to say, "I used an exposure meter that is calibrated; I set the correct film ISO speed; I used the meter according to manufacturer instructions; I set the camera exposure according to the meter; and then I just pressed the button," then I would say, yes, you probably got a good exposure.

Likewise when you say, "I used a monitor calibrated to sRGB" it doesn't really tell me what you actually did. Now, if you were to say, "I calibrated my monitor according to manufacturer instructions (perhaps according to the brightness of the room); I used the hardware 'puck' on the screen, along with the software to make a monitor profile; then I adjusted my images with some 'modern' (color managed) software, and I kept a known-good reference image on the screen for comparison" then I would say that yes, you probably made a good quality image with "proper" color. And if your family and friends did the same thing then they would probably see the same colors that you did.

Beyond that I can't really say, for sure, what anyone will see. Let me give an example - say that your photographer friend views your images one evening, according to these rules. And the next day someone in his family also views the images, same computer, BUT... they opened the draperies with the sun shining into the room. All of a sudden the computer display is gonna seem way too dark. Now, you would hope that they would realize, "hey, I should close the drapes," but these things are not necessarily obvious to everyone.

But for the most part, if your family/friends are somewhat sensible about computer things, and they view your images on a fairly modern system (that uses ICC color management) they are likely gonna see at least decent quality images. (I doubt that most of them will be using monitor-profiling systems.)

Perhaps the easiest way to find out is to ask the people, individually, for their thoughts on the quality. You could even slip in a special "message" in a photo to test... I used to sometimes, for technical reports in the office, put in a line "the first person to see this and call me - I'm buying a beer." So 1) I find out who actually reads it, and 2) for future reports there will be some people wanting to be the first to read it.

 

[pbromaghin]

Thanks Matt for the explanation. But I don't think it answered any of my four questions. Can you or anyone else answer them?


1. Will other viewers who have calibrated their monitor to sRGB "see" the same colors that I see in my photo?

2. Is this true for both those looking at the photos on the web and those looking at the photos from the DVDs I gave them?

3. If I calibrated my monitor to let;'s say Adobe, and then sent them to the web, would the colors look different than what I saw on my monitor?

4. If I calibrated them to Adobe, what would my family see of the DVDs I sent them?

Note that my understanding of this issue is as a career IT guy who had it drilled into me 40 years ago that data must not be messed with. 15 years ago I tried digital photography and when I came across the whole calibration/color space thing I was horrified that it meant messing with data and I headed right back to film.

1)The biggest problem you have is your idea of "calibrating to sRGB". There is no such thing. A "color space" is just an agreed on way of representing the color information of a pixel as 1's and 0's. The "color space" agreement divides the visible color spectrum into slices, each slice represented by a different series of 1's and 0's Every pixel of the same color will have the same 1's and 0's throughout the file.

Calibrating a monitor or printer starts with a file that contains known color values, sending those to the monitor or printer and then comparing what came out with what "should" have come out. The calibration software then does a whole bunch math to come up with adjustments that must be made to each pixel's color data as it goes to the monitor or printer so that the desired color comes out. These adjustment factors as a whole are called the color profile.

Monitors and printers get old and their output changes. It's up to the individual owner to decide how often to calibrate.

2)It doesn't matter where the file came from. Data is just data.

3)Different color spaces use different sized slices. I don't know how this is accounted for.

4)See number 2.

 

[Mr Bill]

@Alan Edward Klein Can I try? I will try not to use jargon too much.

Steven, pretty decent writeup. (Ps, welcome to photrio) But I regret to inform you that it is full of "jargon." If someone already sorta knows what sRGB and AdobeRGB(1988) are, they can sorta follow it. But it takes a deeper understanding, probably beyond most photographers, to get what it means to "do a mapping into 3-dimensional color space," and that sort of thing.

Writing, to be understandable, ought to be written to an "audience," so to speak. So there's a lot of assumptions about what people sorta know as a baseline. If you're talking above that baseline, well... you know how that goes. Sometimes it may be worth trying to explain, in a very basic manner, some of these concepts, just to help lift some people up to that baseline.

Fwiw my "audience" is often the "me" of many years ago, wanting to understand some of the mechanisms of things to some extent. So I try to explain in that vein. I'm sure it's pretty tedious to most people, but... that's just how it is.

Thanks again for weighing in.

 

[MattKing]

@pbromaghin - can you undelete the post you made and then deleted, or tell me to undelete it please?
It is a really good post, and it doesn't just duplicate what others have posted.

 

[pbromaghin]

@pbromaghin - can you undelete the post you made and then deleted, or tell me to undelete it please?
It is a really good post, and it doesn't just duplicate what others have posted.

I had a change of heart and tried to delete it but couldn't figure out how. Please do and thank you for checking with me.

 

[MattKing]

@pbromaghin - can you undelete the post you made and then deleted, or tell me to undelete it please?

It is a really good post, and it doesn't just duplicate what others have posted.

I had a change of heart and tried to delete it but couldn't figure out how. Please do and thank you for checking with me.

Done!
The reference to what calibration actually does - "adjustments that must be made to each pixel's color data as it goes to the monitor or printer so that the desired color comes out" - is, to my mind, really helpful.

 

[runswithsizzers]

Thanks Matt for the explanation. But I don't think it answered any of my four questions. Can you or anyone else answer them?


1. Will other viewers who have calibrated their monitor to sRGB "see" the same colors that I see in my photo?

Kinda depends on what you mean by 'calibrated.' But if the monitor calibration was done properly by both parties, and if you converted the colors of the photo to sRGB color space, and If your photo is tagged with a sRGB color profile, and if your viewer's browser honors the color profile tag, then yes - the photo should look the same on your viewer's browser.

2. Is this true for both those looking at the photos on the web and those looking at the photos from the DVDs I gave them?

It has been a while since I made DVD slide shows, but I don't recall having much trouble with color when played back on my computer. I do remember thinking sometimes the brightness of the DVD playback on the TV was too dark. But back then, I was not using a hardware-calibrated monitor.

However, even if the DVD perfectly matches what you intended, I suspect there is quite a bit of variation in how different viewers will have their TVs adjusted.

3. If I calibrated my monitor to let;'s say Adobe, and then sent them to the web, would the colors look different than what I saw on my monitor?

As others have mentioned, the statement "I calibrated my monitor to [...] Adobe" does not really make sense.

Once you have properly calibrated a monitor using hardware, then - all other things being ideal - the monitor should be able to translate properly between Adobe, sRGB and other color spaces within the monitor's hardware-limited ability to display colors. You can work in any color space you want to, but the safest assumption for the color profile of your output is sRGB. That is, try to export the images that will be shown on the web or displayed on TV screens with a sRGB tag.

Things may have changed since I last investigated, but as of several years ago sRGB was a semi-standard assumption for computer monitirs and TVs intended for average users who don't want to be bothered with the details of color management. This link discusses color spaces and TV/Video, but I can't vouch what he says: https://www.richardlackey.com/choosing-video-color-space/

4. If I calibrated them to Adobe, what would my family see of the DVDs I sent them?

 

[Mr Bill]

The reference to what calibration actually does - "adjustments that must be made to each pixel's color data as it goes to the monitor or printer so that the desired color comes out" - is, to my mind, really helpful.

Well yes, that is exactly ICC color profiles do. Say, for example that you have an image "in sRGB." A typical flesh tone (light-complexion person) might have a set of values R= 230, G =170, B =150. These will represent a "definite color." If you make a monitor profile (using hardware and software - the software flashes a series of RGB values to the monitor; the instrument measures the resulting color; the software creates a profile) it will correlate monitor RGB values to a set of "definite colors."

When the color management system makes the monitor image the sRGB profile and monitor profile work together. It looks at the RGB pixel values (say 230, 170, 150) and uses the sRGB profile to get the "definite color" (in a CIE reference space). Then it finds that same "definite color" in the monitor profile and gets the necessary RGB values that the monitor needs to display that "definite color."

In other words the two profiles, known as an input profile (sRGB) and an output profile (monitor profile) are linked via the "definite color" references, and the monitor pixel values are changed on the fly. To show a correct color.

Fwiw I was gonna try to write up a "brief" explanation with the basic guts of the ICC system but it starts to get pretty wordy. I may still start on it and see if there's much interest.

 

[pbromaghin]

Fwiw I was gonna try to write up a "brief" explanation with the basic guts of the ICC system but it starts to get pretty wordy. I may still start on it and see if there's much interest.

Please do. I spent my career doing accounting, supply chain and payroll - business/ERP work. This area is something about which I know very little.

 

[Steven Lee]

@Mr Bill please do. My understanding of color profiles is quite shallow. The basic principle is that the color we see is "analog" i.e. is defined by a wavelength of light. What we perceive as "red" commonly lies somewhere on a spectrum from 600nm to 750nm.

Now, assume you have a digital RGB value of 255,0,0 which basically says "pure 100% red". But where exactly on that range between 600nm to 750nm this particular "red" is? Your monitor does not know. That's what color spaces do: they map digits representing color to "analog" color. Then a monitor knows to take 255,0,0 value and emit 695nm light (for a given colorspace), for example.

Since each digital color is 3 digits, it's convenient to think of it as a vector in 3D space. So the digits become coordinates in a colorspace.

And from there, we get to color transformations. My suspicion is that ICC and similar technologies (like DCP) define matrix transforms from one colorspace to another?

 

[Kino]

DisplayCAL—Display Calibration and Characterization powered by ArgyllCMS

Display calibration and profiling with a focus on accuracy and versatility

displaycal.net

If you want to scroll down through the information on the landing page, its all there in head-splitting detail.

It all comes down to how accurate you HAVE to be versus how accurate you can tolerate.

You will soon see why digital production facilities have full-time color management people.

It is not a simple thing across so many digital color spaces and with poor information on what is and is not color managed in your computer.

I use Displaycal to calibrate my "hero" monitor that I use to color grade digital video images. My workstation monitors are calibrated to the Rec. 709 color space used in HDTV production. I use a X-Rite puck with the Displaycal software and feed a signal through my Blackmagic 4K output card to my Dell "hero" monitor, which then measures a large number of color patches and creates a profile which is saved. This profile is then loaded into DaVinci Resolve Color Correction software, which applies this profile to the output of the 4K Blackmagic card to tune the color reproduction as close as possible to Rec. 709.

As for my "Main" computer monitor, I have to do the same thing, only it does not feed the signal through the Blackmagic card, but through my main video display card and generates yet another profile. This profile is then automatically loaded into my main display via an application that starts on booting my computer and makes my main display as close to Rec. 709 as possible.

If I wish to edit photos for web use (sRGB color space), I have to defeat the application and reboot to return to the default sRGB profile as loaded by my Nvidia card.

You can generate any number of profiles for your monitor(s) in just about any color space you want and load or unload them at will. The accuracy of these profiles depend on the quality of your monitor and what colorspaces it can accurately reproduce. Of course, the better the reproduction, the higher the cost, but this is getting better with the march of time. Most modern, medium range monitors will easily cover sRGB, but will decrease in accuracy as you go "up" in the colorspace list. The still photo order is roughly -- sRGB, Adobe RGB and Prophoto RGB. Digital video standards include Rec. 709 (HDTV), DCI-3 (Digital Cinema) and Rec 2020 (ultra expensive).

 

[Mr Bill]

Ok, I'll get going on a writeup, probably in parts.

My suspicion is that ICC and similar technologies (like DCP) define matrix transforms from one colorspace to another?

Actually when a device has to be sampled the standard method is to use a set of 3-d LUTs. Obviously this can eat up a lot of space real fast, so only a relatively small number of points are sampled. Then the color-management engine has to interpolate most of data. They do typically use a matrix transform for adaptation between light sources in the reference color space. (I'm not much on the math; I just know that these are the general methods.)

 

[Kino]

Thanks Matt for the explanation. But I don't think it answered any of my four questions. Can you or anyone else answer them?


1. Will other viewers who have calibrated their monitor to sRGB "see" the same colors that I see in my photo?

If taken at face value: yes, more or less so. It should be very close.

2. Is this true for both those looking at the photos on the web and those looking at the photos from the DVDs I gave them?

Only IF the DVDs are played back on a computer that is using the sRGB color space. If played on a dvd player to a modern large screen TV, most likely not, as it uses the Rec. 709 color space for HD Television. The colors will shift somewhat as the "red" on sRGB is not exactly the same "red" on sRGB (and so for each color). Even an old CRT color tube uses a different color space than sRGB...

3. If I calibrated my monitor to let;'s say Adobe, and then sent them to the web, would the colors look different than what I saw on my monitor?

Yes.

4. If I calibrated them to Adobe, what would my family see of the DVDs I sent them?

If they use a computer in sRGB, they would see a slight shift, but probably not enough to be objectionable. Most people wouldn't really notice or care.

 

[Alan Edward Klein]

OK I set the calibration for Spectraview II to sRGB and then hit calibrate. Of course, the puck was connected already and mounted on the NEC PA242W monitor display. It then spends ten minutes going through all these color changes. Done. I guess I'm setting the monitor for the sRGB color gamut. AM I?

After its done, I have these setting results:

 

[Kino]

Yes. I am unfamiliar with the Spectraview, but assume it will save the profile to windows profile settings. As long as it does that, you are in sRGB.

 

[Alan Edward Klein]

Kinda depends on what you mean by 'calibrated.' But if the monitor calibration was done properly by both parties, and if you converted the colors of the photo to sRGB color space, and If your photo is tagged with a sRGB color profile, and if your viewer's browser honors the color profile tag, then yes - the photo should look the same on your viewer's browser.

It has been a while since I made DVD slide shows, but I don't recall having much trouble with color when played back on my computer. I do remember thinking sometimes the brightness of the DVD playback on the TV was too dark. But back then, I was not using a hardware-calibrated monitor.

However, even if the DVD perfectly matches what you intended, I suspect there is quite a bit of variation in how different viewers will have their TVs adjusted.

As others have mentioned, the statement "I calibrated my monitor to [...] Adobe" does not really make sense.

Once you have properly calibrated a monitor using hardware, then - all other things being ideal - the monitor should be able to translate properly between Adobe, sRGB and other color spaces within the monitor's hardware-limited ability to display colors. You can work in any color space you want to, but the safest assumption for the color profile of your output is sRGB. That is, try to export the images that will be shown on the web or displayed on TV screens with a sRGB tag.

Things may have changed since I last investigated, but as of several years ago sRGB was a semi-standard assumption for computer monitirs and TVs intended for average users who don't want to be bothered with the details of color management. This link discusses color spaces and TV/Video, but I can't vouch what he says: https://www.richardlackey.com/choosing-video-color-space/

If my monitor is set for Adobe RGB let's say, won't the colors be changed when I send the photo to the web as sRGB? If that happens, why not set the monitor for sRGB to begin with so the web colors match my monitor colors to begin with.

 

[Kino]

sRGB is the defacto standard for Web-based images, however SOME web browsers can handle color management and will properly display other color spaces.

Practically speaking, your best bet is to stay with sRGB, as their are no uniform implemented standards.

 

[Alan Edward Klein]

If taken at face value: yes, more or less so. It should be very close.


Only IF the DVDs are played back on a computer that is using the sRGB color space. If played on a dvd player to a modern large screen TV, most likely not, as it uses the Rec. 709 color space for HD Television. The colors will shift somewhat as the "red" on sRGB is not exactly the same "red" on sRGB (and so for each color). Even an old CRT color tube uses a different color space than sRGB...


Yes.


If they use a computer in sRGB, they would see a slight shift, but probably not enough to be objectionable. Most people wouldn't really notice or care.

Thanks. You answered my questions. Since I only intend to send photos to the web, I;ll keep adjusting my photos with my monitor adjusted for sRGB That way what I see on my monitor, will be on the web. I can't see adjusting to a color space that will change the colors when it's sent to the web.

 

[Kino]

That's the safest bet for sure...

 

[MattKing]

Yes. I am unfamiliar with the Spectraview, but assume it will save the profile to windows profile settings. As long as it does that, you are in sRGB.

One thing to be cautious about - you need to be sure that the new profile that your Spectraview determined for you is actually the one in use. If you work with a bunch of profiles, you can end up with a list, and you want to make sure that the newly calibrated profile is the one that the system defaults to.

 

[Alan Edward Klein]

One thing to be cautious about - you need to be sure that the new profile that your Spectraview determined for you is actually the one in use. If you work with a bunch of profiles, you can end up with a list, and you want to make sure that the newly calibrated profile is the one that the system defaults to.

Yes thanks for that. It appears I always use the same selection as you can see in the photo in my above post.

 

[Alan Edward Klein]

That's the safest bet for sure...

Thank you and thank everyone else for their help.

 

[runswithsizzers]

OK I set the calibration for Spectraview II to sRGB and then hit calibrate. Of course, the puck was connected already and mounted on the NEC PA242W monitor display. It then spends ten minutes going through all these color changes. Done. I guess I'm setting the monitor for the sRGB color gamut. AM I?

After its done, I have these setting results:

It concerns me that you have selected "Maximum posssible" for the Intensity setting. If your work space is very brightly lit, that may be appropriate, but I think many people have their monitors set too bright. I believe it is common for the calibration software to make the user choose a brightness level, tho some have a mechanisim to measure the room ambient light level and pick an appropriate value.

What is an appropriate value? According to this website: https://www.cambridgeincolour.com/tutorials/monitor-calibration.htm
"...the optimal luminance setting is heavily influenced by the brightness of your working environment. Most people set the luminance to anywhere from 100-150 Cd/m2, with brighter working environments potentially requiring values that exceed this range. The maximum attainable luminance will depend on your monitor type and age, so this may ultimately limit how bright your working environment can be."

Not sure if the calibration is still valid if you change the monitor to some other brightness level after you calibrate.

This website has a series of test images which may help you evaluate if you monitor is displaying images properly: http://www.lagom.nl/lcd-test/

 

[Alan Edward Klein]

It concerns me that you have selected "Maximum posssible" for the Intensity setting. If your work space is very brightly lit, that may be appropriate, but I think many people have their monitors set too bright. I believe it is common for the calibration software to make the user choose a brightness level, tho some have a mechanisim to measure the room ambient light level and pick an appropriate value.

What is an appropriate value? According to this website: https://www.cambridgeincolour.com/tutorials/monitor-calibration.htm
"...the optimal luminance setting is heavily influenced by the brightness of your working environment. Most people set the luminance to anywhere from 100-150 Cd/m2, with brighter working environments potentially requiring values that exceed this range. The maximum attainable luminance will depend on your monitor type and age, so this may ultimately limit how bright your working environment can be."

Not sure if the calibration is still valid if you change the monitor to some other brightness level after you calibrate.

This website has a series of test images which may help you evaluate if you monitor is displaying images properly: http://www.lagom.nl/lcd-test/

I am able to see the black and whites in that test although two or three of the darkest blacks seem very close. If my screne was darker, more of the black would blend. It is bright in my room right now.

My setting for luminance is 217Cd/m2. I didn't set the highest selection. I just left everything at default when I calibrated the monitor. Why does it matter? How does the brightness level of the monitor affect the final image that goes out as a file to the web? It doesn't change it. I use the histogram to set levels to avoid clipping. So luminance should not affect that. Of course contrast, and some of the other sliders would be affected. I guess looking at the results would be the best way to tell if I'm getting good results. So maybe you can help me there.

Here are samples adjusted at this level. Do they look OK to you? These were shot as jpegs with a digital camera.

Red Rock Canyon, Las Vegas

Explore this photo album by Alan Klein on Flickr!

www.flickr.com

Here are samples of 4x5 Velvia 50 film scanned. A lot more adjustments had to be done so these are more critical. I used the same Cd luminance level as for the digitals

4x5 Color Large Format

Explore this photo album by Alan Klein on Flickr!

www.flickr.com

For both sets especially the film scans,
1. Does the brightness seem OK?
2. Contrast OK?
3. Shadows and highlight areas OK?
4. Do colors look normal? (they may look a little saturated as I saturated the digitals a little and the second set was Velvia 50s with high saturation in the film.)