[michael10003]

I've been reading up on color spaces, calibration/profiles, and trying to implement an optimal workflow (using retina macbook pro and Mac mini w 27" QHD monitor). I've learned a great deal from many a forum and site. But there's one question that nobody seems to answer, and I feel like I'm in the Twilight Zone trying to figure it out. It's also preventing me from moving forward with confidence.

I understand the purported benefits of ARGB. But aren't those benefits contingent on being able to see them? On a similar note, if you don’t need a wide gamut monitor to work with AdobeRGB, what are those monitors for?

The monitor I purchased is standard gamut, and claims to reach greater than 99% sRGB. So if I'm working in sRGB (capturing photos, Lightroom, Photoshop workspaces, etc), all's good. What you see is more or less what you get, right? I’m not sure what my monitor's claim is for ARGB. But I think usually for even the good sRGB monitors, it’s somewhere in the 70s (%) or 80s. So let's say my monitor achieves 75% AdobeRGB. If my monitor can’t display 25% of that color space, how can I see those colors? If I can’t see those colors, what business do I have making edits to a photo which uses them? That seems crazy to me!

So, what's the point in using the AdobeRGB color space - for image capture, editing, or output - if my monitor can't resolve those colors? Would I be working blind? And would that be better than working more or less 1:1 with an sRGB color space?

My other question is this: Should I set my resolution in my image setup to match that of my display’s pixel pitch? If not, why isn’t this ideal?

My monitor is 27" diagonal; 2560 x 1440. That breaks down to about 108ppi. So when setting up workflow options in photoshop, what's going on if I set "resolution" to, say, 300ppi? How can the display show more "pixels" of image when there physically aren't that many pixels in a given parameter (one inch) to display them? Or rather, how is it possible to have an image resolution greater than your monitor’s? I imagine I'm confusing the meaning of pixels here, and maybe resolution too. Because, to use an example from TV which I think I do understand, we can't display a 4K image on a 1080p screen. Because there just aren't enough horizontal or vertical lines (of pixels). So, back to computers and picture making: how can I set my canvas to 300ppi or 150ppi, when my display only has 108ppi?

Thank you to anyone taking the time to help. I've been stumped!

Michael

 

[fhoech]

I understand the purported benefits of ARGB. But aren't those benefits contingent on being able to see them?

Depends on what your goal is. If you just want to (e.g.) archive AdobeRGB images your camera spits out, for the potential future purchase of a wide-gamut monitor or printer, for example, it may make sense.

On a similar note, if you don’t need a wide gamut monitor to work with AdobeRGB, what are those monitors for?

Well, but you do Even if all you want to do is ultimately print on an inkjet with relatively wide gamut on glossy paper, you'll be able to make better edits if you're able to see what you're actually doing to very saturated colors (although for print, AdobeRGB is not even that good of a choice - some inkjets have gamuts wide enough that ProPhoto becomes a viable option if you want to preserve all color detail. Not because the printer gamut would be as huge as ProPhoto - not even close - but because additive RGB matrix spaces need to be a lot bigger than the gamuts of printers which are devices with subtractive color mixing, whose comparatively dark saturated colorant "primaries" would otherwise not fit inside the RGB space if its primaries weren't dark enough. And for RGB matrix color spaces, the only way to make primaries darker is to make them more saturated).

The monitor I purchased is standard gamut, and claims to reach greater than 99% sRGB. So if I'm working in sRGB (capturing photos, Lightroom, Photoshop workspaces, etc), all's good. What you see is more or less what you get, right?

More or less, yes.

I’m not sure what my monitor's claim is for ARGB. But I think usually for even the good sRGB monitors, it’s somewhere in the 70s (%) or 80s. So let's say my monitor achieves 75% AdobeRGB. If my monitor can’t display 25% of that color space, how can I see those colors? If I can’t see those colors, what business do I have making edits to a photo which uses them? That seems crazy to me!

Quite right imo.

So, what's the point in using the AdobeRGB color space - for image capture, editing, or output - if my monitor can't resolve those colors? Would I be working blind? And would that be better than working more or less 1:1 with an sRGB color space?

It depends on the images you work with. Even if an image is in AdobeRGB doesn't necessarily mean the image gamut makes use of the whole space. A picture of skin or other muted tones fits often times perfectly within sRGB (unless you use some wild lighting).

My other question is this: Should I set my resolution in my image setup to match that of my display’s pixel pitch? If not, why isn’t this ideal?

I think you mean optical resolution (dpi) not pixel pitch? The optical resolution is only an indicator how many pixels should be mapped to a potential output medium, e.g. 300dpi means the image should be scaled such that one inch on the output medium should be covered by 300 pixels. For display, it has no real meaning, as you can adjust the interpolation by zooming the image.

My monitor is 27" diagonal; 2560 x 1440. That breaks down to about 108ppi. So when setting up workflow options in photoshop, what's going on if I set "resolution" to, say, 300ppi?

Unless you print, nothing.

How can the display show more "pixels" of image when there physically aren't that many pixels in a given parameter (one inch) to display them?

It can't. If you zoom the image so that one inch on screen is the equivalent of 300 pixels, those pixels will be interpolated.

Or rather, how is it possible to have an image resolution greater than your monitor’s?

It only is of use if you're outputting to a device that has a high enough resolution (e.g. a printer).

I imagine I'm confusing the meaning of pixels here, and maybe resolution too. Because, to use an example from TV which I think I do understand, we can't display a 4K image on a 1080p screen. Because there just aren't enough horizontal or vertical lines (of pixels).

Well, you can, but the result would be a scaled down (interpolated) to 1080p version of the image.

 

[michael10003]

I think I'm understanding. Seems I should continue taking pictures with the dual RAW/jpeg setting. Then I can work with the RAW and wider gamut later on down the technicolor road, and more immediately edit jpegs in my sRGB world. As for drawing and painting, I'll use an sRGB space, as I want to be know the colors I'm creating.

The optical resolution is only an indicator how many pixels should be mapped to a potential output medium, e.g. 300dpi means the image should be scaled such that one inch on the output medium should be covered by 300 pixels. For display, it has no real meaning, as you can adjust the interpolation by zooming the image.

Copy that. So the resolution (ppi) setting in photoshop when creating a new image pertains to its potential output.

Thank you very much fhoech...

 

[spacediver]

These are really good questions, and I don't have a solid grasp on them, but I'll attempt to shed some light, and hopefully others who have sharper knowledge can improve upon or correct my reply.

So, what's the point in using the AdobeRGB color space - for image capture, editing, or output - if my monitor can't resolve those colors? Would I be working blind? And would that be better than working more or less 1:1 with an sRGB color space?

When it comes to image capture, I think this is how it works. The camera captures the exact same raw information regardless of what colorspace you set the camera to. The values of each pixel in the raw image is determined by the spectral transmission of that pixel's particular filter combined with the spectral power distribution (SPD) of the light that passes through that particular pixel's filter. Using various algorithms, groups of these raw pixel values (each group contains red, green, and blue filtered values) are averaged with a weighted sum* to produce a single triplet of numbers, such as [50 70 200]. If the camera is set to sRGB, the idea is that when an sRGB display device renders the red channel at a value of 50, the green channel at a value of 70, and the blue channel at a value of 200, the resulting color that the display renders will match the color of the portion of the scene that is represented by that pixel. Of course, this is an imperfect process for at least two reasons:

1) the camera has no way of knowing what the spectral power distribution of the incoming light from the scene is, and as described earlier, the value of the raw pixels depend on the SPD of this incoming light. So assumptions have to be made, and the more the assumptions don't match reality, the less accurate the color encoding will be.

2) Even if the camera knew what the spectral power distribution of the incoming light was, and adjusted its weighted averaging accordingly, it is possible that parts of the scene contain colors that are more saturated than can be represented by a particular color space, such as sRGB. In that case, color information has to be shrunk down to fit a particular color space.

With respect to this second point, suppose you are imaging a very saturated green surface, one whose color exactly matches the top corner of the triangle defined by the Adobe RGB color space, and suppose that the camera's assumptions about the SPD are spot on. In such a situation, if you set the camera to Adobe RGB, then the resulting value for all pixels capturing that green surface would be [0 255 0] (in an 8 bit context), and, on a display that is capable of rendering the full Adobe RGB color space, the displayed surface would match the color of the surface in the scene. However, if the display that is rendering this image is an sRGB display, the resulting color will now correspond to the top corner of the sRGB color space. If you look at the image from the previous link, you will note that the the hues (in addition to the saturation) for the top corners of Adobe RGB and sRGB differ. So rendering this image on an sRGB display will not only show a less saturated green, but will get the hue wrong. However, if you had selected sRGB on the camera, the weighted averaging may now encode an sRGB coordinate that perfectly matches the hue of the surface. Of course, by representing the hue accurately, the saturation of the green is now even less than the most saturated green that the sRGB display is capable of, but this tradeoff may be acceptable. Of course, different schemes may prioritize different aspects of color, so other weights may favor saturation over getting the hue just right. And of course, don't forget point 1 above, which is that the assumptions about the SPD of the incoming light are just that: assumptions.

Hopefully this discussion will give you the tools to think about what happens with other conditions, such as when the camera is set to sRGB and the image is rendered on an Adobe RGB display.

As for image editing and output, I'm delving more into speculation here, but I think the general idea is the same. Say you load up that image that was captured using the Adobe RGB camera setting, and render it on a display that is capable of rendering the full Adobe RGB space. You now save it but want it to be encoded in sRGB (you assume that most people use sRGB displays). If all the pixels in the image you are working on are the same, and are [0 255 0], and you save it in sRGB, then the pixels will now have a different triplet: one that when rendered on an sRGB display, will match the hue of the original image (and again, some software will allow you to make different tradeoffs when re-encoding the image).


As for ppi, I don't have much experience with raster programs, but in a vector based program, it's easier to think about. The ppi that you save the image in will be the true image resolution. Of course, if your display is incapable of rendering that density of ppi, then it will have to magnify the image to compensate.


*I've skipped a step for brevity. After this averaging, a demosaicing process uses a sliding window so that the resulting image does not suffer a loss of resolution. See http://www.cambridgeincolour.com/tutorials/camera-sensors.htm for more information.

edit: fhoech beat me to it, while I was writing this post

 

[michael10003]

This is great. Okay..

The camera capture the exact same raw information regardless of what colorspace you set the camera to.

Right, RAW has no colorspace until one is assigned in an editor, right? And setting of the colorspace in camera is for jpeg?

... So rendering this image on an sRGB display will not only show a less saturated green, but will get the hue wrong. However, if you had selected sRGB on the camera, the weighted averaging may now encode an sRGB coordinate that perfectly matches the hue of the surface. Of course, by representing the hue accurately, the saturation of the green is now even less than the most saturated green that the sRGB display is capable of, but this tradeoff may be acceptable. Of course, different schemes may prioritize different aspects of color, so other weights may favor saturation over getting the hue just right.

This is very clearly explained. Thank you. Is this what 'rendering intents' are about? I think the only place I've seen having the ability to choose which rendering intent to implement when profiling a display is in dispcalGUI. If what you describe above is pertaining to rendering intents, then it seems a very important decision, how to "cheat" that missing information. (must re-read the amazingly informative yet slightly intimidating dispcalGUI manual!) Okay, so say I've decided to work in sRGB in all my color-managed apps. And I've chosen a rendering intent when calibrating and profiling my display. Should I use that profile in all my apps? Or stick with something like sRGB IEC61966-2.1, which photoshop offers up as default? Sorry, I'm improvising questions here.

These are really good questions, and I don't have a solid grasp on them, but I'll attempt to shed some light,

I think you have a pretty good grasp! This is all very helpful. Thank you...

 

[spacediver]

Right, RAW has no colorspace until one is assigned in an editor, right? And setting of the colorspace in camera is for jpeg?

Yes, I believe so. In the normal use of the term "colorspace", the RAW image has no colorspace until either an editor weights/demosaics or until the camera software itself does the same transformations.

This is very clearly explained. Thank you. Is this what 'rendering intents' are about? I think the only place I've seen having the ability to choose which rendering intent to implement when profiling a display is in dispcalGUI. If what you describe above is pertaining to rendering intents, then it seems a very important decision, how to "cheat" that missing information. (must re-read the amazingly informative yet slightly intimidating dispcalGUI manual!)

Yep, I believe you have this right. fhoech (who is the author of dispcalGUI) likely knows more about this, and your question about which profile to use.

 

[fhoech]

Is this what 'rendering intents' are about?

A "rendering intent" in ICC terms is something quite specific, technically it boils down to a selection (or rather preference) for a particular table in a table-based (=LUT) profile, that should be used during the actual color transformation. There are three intents:

• Colorimetric (this includes absolute and relative colorimetric). Used for colorimetrically accurate color transformation as far as possible (out of gamut colors will be clipped).
• Perceptual. This is meant to be used to give a pleasing rendering of large gamut source material in a smaller destination gamut (the source gamut is usually compressed). Not meant to be colorimetrically accurate. Useful for e.g. converting photos to a print color space.
• Saturation. This is meant to be used to giving a pleasing rendering of source material in the destination gamut, with a focus of retaining saturation. Not meant to be colorimetrically accurate. Useful for e.g. converting line art/vector graphics to a print color space.

To explain this further, matrix profiles can only support one intent: Colorimetric.
Table-based profiles can (but don't have to) support two additional intents: Perceptual and saturation. Both of these intents are not specified in terms of gamut mapping (atleast for ICCv2). So, profile creation software is basically free to do whatever it wants when creating these two tables, if it even creates them at all (typically a vendor-specific source space is assumed, or a configurable one like with Argyll CMS), and will use some form of gamut compression (e.g. for perceptual intent) and/or expansion (e.g. for saturation intent) to map source colors into the destination colorspace.
Most applications using ICC profiles for color transformations allow a selection of all rendering intents, even if the profiles involved don't support them, and fall back to colorimetric silently, so they give the false impression that all intents are always available.

I think the only place I've seen having the ability to choose which rendering intent to implement when profiling a display is in dispcalGUI.

There are two locations in dispcalGUI where you can choose a rendering intent: In the advanced gamut mapping options for LUT profiles (although the default intent selection only sets a hint in the profile, that most applications actually ignore, so it's somewhat pointless to set), and in the 3D LUT options.
You can tell Argyll CMS to create the aforementioned perceptual or saturation tables, by choosing a source profile and selecting a gamut mapping for perceptual and saturation intents (=tables), which influences what kind of gamut mapping those tables will contain. Usually, for display profiles, you don't necessarily need those, as you'll want colorimetric accuracy, and not all applications offer a choice of rendering intent for the display profile (e.g. Photoshop doesn't unless you use a custom sofproof setup). Those tables may be of use though, if you want to work with large gamut images on a standard gamut display (I'd still not recommend it though). In such a case, you would select the most common large gamut color space of your images (e.g. Adobe RGB) as source profile.

Okay, so say I've decided to work in sRGB in all my color-managed apps. And I've chosen a rendering intent when calibrating and profiling my display. Should I use that profile in all my apps? Or stick with something like sRGB IEC61966-2.1, which photoshop offers up as default?

Sorry, I'm not sure I understand the question. Photoshop will automatically recognize and use the currently assigned display profile, and doesn't offer up a method to select something different. What you can change are the working space profiles, and since you want to work mainly with sRGB images, it makes sense to use that.
Other applications may require more configuration, e.g. the Gimp needs to be told explicitly to use the system configured display profile.

 

[michael10003]

Sorry, I'm not sure I understand the question. Photoshop will automatically recognize and use the currently assigned display profile, and doesn't offer up a method to select something different. What you can change are the working space profiles, and since you want to work mainly with sRGB images, it makes sense to use that.
Other applications may require more configuration, e.g. the Gimp needs to be told explicitly to use the system configured display profile.

Forgive me, I was condensing several trains of thought. I'm not sure I can make sense of it myself. I was speaking about when I create a new document, and I get the new document window:

If I click on 'Color Profile' I can choose, among the many stock profiles, any of the custom profiles I've made. So I was wondering if it's better to plug in the same profile I'm currently using for my display (which as you say Photoshop is automatically already using) for a new document, or to use the sRGB one that's suggested there in the dialog.

This confusion of mine carries over likewise to the working space, which as you also mention, one can change. Per Photoshop help: "The RGB Color mode in Photoshop varies according to the working space setting that you specify in the Color Settings dialog box."
When you say

What you can change are the working space profiles, and since you want to work mainly with sRGB images, it makes sense to use that.

...are you meaning I should use the sRGB IEC61966-2.1 that Photoshop suggests (same as in new document), or that I should input my own display profile? Or something else?

Thank you very much fhoech, and spacediver, this has already been super helpful. And thank you fhoech for your excellent software. The bar for what I expect myself to understand regarding color representation has been raised, in large part because when I first opened dispcalGUI, I quickly realized how woefully unprepared I was for the control being offered. So it was really satisfying, once I finished the Read Me guide (which as I said, begs re-reading), to actually run the processes and feel like I knew at least a little bit about what I was doing.

(Unfortunately, I repeatedly ran into issues with certain aspects of Yosemite - mostly in its transparency effects being discolored - in the newly created profiles, and so went about using the i1DP kit software for my initial calibrations. But as I learn more, and get less precious about the whole process, I'll be returning to dispcalGUI, because I think it rocks)

 

[fhoech]

Don't assign your actual monitor profile as working space or document profile, that doesn't make much sense. sRGB in your case would be the right choice.

 

[michael10003]

Very good. Thank you sir.

 

[Kukulcan]

I gave a quick look to this thread, don't know if already said, but please micheal10003 consider that most of your doubts have to do with printing stuff!
Photo inkjet printers today are capable of huge gamut, far beyond the sRGB, and even beyond AdobeRGB, and photographers want to exploit these gamuts.
Also the set resolution (300 ppi) is strictly related to the print size you're going to do. Understanding rendering intents is also crucial before printing, when a high degree of visual match is desired.

 

[michael10003]

(This post began as a simple reply, and developed into something beyond. Pardon if disjointed)

...consider that most of your doubts have to do with printing stuff!

I'm starting to realize this. Thanks...

BTW, just wondering, looking at an image/photo on a display, is there any way to know which, if any, colors were out of gamut, and have been clipped or compressed (or otherwise dealt with)? Assuming the rendering intent chosen is "best" for the circumstances, and there's no banding or other artifacts left in its wake. Is there a way to tell?

It reminds me, for some reason...

Hopefully this discussion will give you the tools to think about what happens with other conditions, such as when the camera is set to sRGB and the image is rendered on an Adobe RGB display.

I used to think there was a small portion of sRGB (in the blues?) that was actually out of AdobeRGB's gamut. But according to this graph Adobe RGB color space it appears that all of sRGB is contained within ARGB. So I don't know - seeing as technically ARGB can "handle" anything sRGB throws at it, I'd say where we might be able to discern distortions or variances would be in the transitioning, the gradations of colors represented? Because AdobeRGB has much more potential color to work with, but is still governed by the same 1-255 units of... luminance? Or color? This is why I think they say sRGB can be preferable to AdobeRGB when dealing with colors that are within both color spaces (that is, within sRGB). Because it ostensibly handles variance with greater subtlety? So if we loaded an sRGB image into an AdobeRGB workspace, the gradations between two extremes of luminance might be more choppy?

On the other hand, if I found myself photographing David LaChapelle's birthday party, and the camera was set to sRGB, and I uploaded pics into ARGB space (or sRGB for that matter), viewers would likely never know what I had seen, because the real world gamut was greater than my captures... ?

Don't assign your actual monitor profile as working space or document profile, that doesn't make much sense. sRGB in your case would be the right choice.

I think I understand the reason why it doesn't make much sense. Because a particular device's profile is the way we modify its specs, so it's able to accurately represent the respective "standard" that the device was calibrated against? (in this case sRGB). There's a universal profile for each of these given spaces. And in setting up the workspace options, Adobe is saying, "we'll use this standard [sRGB], and your monitor will use its own profile so that you see, as closely as possible, this standard represented on your particular machine."

So, setting Adobe's work space to my display's profile would actually be imposing settings that weren't really sRGB, but a series of equations that get a device able to represent sRGB. Therefore, I would be wreaking information havoc on images that were "accurately" weighted or demosaiced or otherwise processed through the camera's (sRGB) profile.

?? Am I ballpark here? I think I'm ballpark..

But then I don't know why Adobe offers me the option to assign my monitor profile there. Although I suppose one might find something worthwhile in the results. Happy accidents, and such.