A well calibrated monitor implies that this is adjusted to a standard. Of course, higher the standard (and the system), better the color reproduction. As general rule, if the specs are not well adjusted according to the standard, then it could be an issue either in the predefined non-linear response, chromaticities or viewing conditions. If in spite of that, you don't get a good color reproduction, then the issue is probably in the color workflow. As general rule also, if you don't have a system for profiling and calibrating, then install and use (in your OS) the color profile that comes with your monitor drivers, this will be always better (sometimes surprisingly much better) than the generic profile assigned by default by the OS.
Let's remember that RGB and CMYK are color models and in the same way there are many RGB color spaces, there are also many CMYK color spaces with different gamut ranges. Gamuts are three-dimentional and even when USWebCoatedSWOP2 is smaller than sRGB, small portions of greens, cyans and a bit of yellows are not contained by sRGB.
Modern CMYK color spaces (mostly those working for multichannel printers or Giclee printing) may have wider gamuts, not all real colors, but a sRGB ouput will surely not be enough.
A comparison of these profiles can be visualized more easily in a gamut 3D viewer. Don't know many free apps that can do this, but on Mac, the Colorsync control panel can be useful. I remember there was a Color Control Panel Applet for Windows XP but don't know if it works with Win7. There's also PerfX Gamut Viewer for Win and Mac which can plot 4 profiles at the same time. The trial version of Gamutvision might help too.
After checking, if the difference of reproducible colors between RGB and CMYK is not much, a color conversion at the end of the process (in PS, LR or similar), may be enough. But if the gamut difference is too high in our final colors, we'll want to know how things will look like from the moment the image is generated. This phase is when is more easy and flexible adjust the color appearance and there's where a CMYK preview is more convenient.
Press Release of LW 10.1 said that it supports color space correction for CMYK data and LW documentation addendum (What's new in v10.1) says that linear color space supports ICC/ICM monitor profiles and after that, between parenthesis, it states that it supports, among other color models, CMYK data. It's confusing because one might think that this data could be got through ICC/ICM profiles - which is the standard profile format that has proven to work for this type of conversions in print industry - but pitifully this is not the case. Not for previewing or converting from/to CMYK ICC profiles (DepthX supports JPGs with CMYK (YCCK) data, btw). It should be referring to the LUT color tables, but without a Color Management (CM) system to generate and handle color models conversions and color space conversions through LUTs appropriately, which is prohibitive for the common CG artist/pro or small/medium studio, this is not a viable option. Good LUTs generators are not cheap neither (LUT generation services can cost between $100 to $5000) and a 3D LUT alone won't work as expected for this, since the ASC/CDL LUT standards have not defined specifications about color spaces, viewing conditions, nor gamut mapping; then without those expensive LUT-based CM systems, able to handle these aspects and others (and if they even can handle 4D LUTs) - there's no way to get a predictable and consistent color appearance. Even several LUT-based CM modules have some serious issues with this type of color conversions (mostly for device-dependent representations) - we are talking about a 4 channel color model here - guess that's why ICC/ICM profiles are used instead (besides, ICC profiles are either cheap or free). Other situation is that for print work (and for film work too) we need concatenate color conversions, seeing that a single one (and a single type of LUT) can not handle the right color appearance appropriately in these cases. But 3D LUTs that concatenate color space conversions won't work well without a CM module. Also, concatenating single color tables is not currently possible in the CS panel and it seems the useful db&w Colour Space node doesn't load ICC/ICM profiles like in the CS panel, and guess that a CMYK ICC profile won't work there too since these are output profiles, not display profiles. LW would need a strongest ICC/ICM support for solving these color conversions natively in a cheaper and easier way so that the common user or small/medium studio can have available these kinds of previews.
SG_CCTools can handle CMYK data, but the available version presents artifacts in this type of conversions. I use here an unreleased version that doesn't present artifacts (and works in LW11), but CMYK conversions are not so straightforward since the color and vector inputs/outputs only allow 3 channels and CMYK data needs 4 input channels, so there's a corrupted output in the SG_CCNode. I've been able to solve this with an Abstract profile, which basically performs the conversion internally in a single profile and outputs the correct colors. Sebastian Goersch (the developer) is working in a new version in his spare time (that promises to be better than the one I currently use), but due to the improvements of the CMM, it's like re-doing the whole thing from scratch again, and it seems this gonna take time. If you guys and girls are interested, please let him know that a new version will be very welcome :thumbsup:. His email
(or a donation link) is in the
SG_CCTools web page.
The results we can get in this way compared with Photoshop are these:
I haven't seen this kind of CMYK previews in no other 3D package before
Now, without a preview possibility within LW, there's still a way to get a rough approach. I'd recommend to use the SG_CCPicker (free), or Jovian Color Picker (commercial) to load a screen capture of a CMYK pantone/color wheel within LW to guide your color choices in RGB space. The pantone should contain the most saturated colors that the CMYK model is able to reproduce, so that you don't surpass them. It's not ideal since color/hues relationships won't be the same, but it's better than nothing.
To install SG_CC Picker, just place it in your plugins folder, add it manually in LW and select it in the General Preferences as your color picker. A screen capture of a color wheel or pantone (up to eight) can be saved as images of 128x384 pixels and load them in the Config Panel of the picker. SG_CCPicker is able also to pick colors from any other image or app running on the screen.
The installation of the SG_CCNode and the SG_CCFilter is indeed more complex due to the color profiles list. Besides, the released version doesn't work in LW11, but if someone wants to try in LW9.6, I would recommend skip the python script for the installation since without a previous version of Python, the script won't work. Then it's easier install them by hand. Create a new folder in your plugins folder (SG_CCTools or something like that) and unzip the plugins there. In the same folder, create a .txt file called colorprofiles.txt. Identify the route in your system of each color profile you want to use in the filter or the node and copy each route there. The colorprofiles.txt would be something like this:
C:\Program Files (x86)\Common Files\Adobe\Color\Profiles\AdobeRGB1998.icc
C:\Program Files (x86)\Common Files\Adobe\Color\Profiles\sRGB Color Space Profile.icm
C:\Program Files (x86)\Common Files\Adobe\Color\Profiles\ProPhoto.icm
C:\LogProfiles\MyMonitor.icc
...and so on. Then within LW, install the plugins as usual.
In case someone wants to use SG_CCTools for preview more accurate colors in linear workflow, you can create the linear profiles with Photoshop as is described at the end of
this post.
Sorry for the missing images in the linked thread but the server that stores my images has been hacked - until solving that, if the linearization method is not understandable without the images, I can re-post the method here with new images.
Gerardo