Justin has a valid point; the perceptual display difference from within Maxwell Render compared to within Photoshop is worrying for anyone used to the regular colour managed workflow. Maybe a recap of the latter will help to find out where the problem lies:
- Monitors, scanners and cameras use the additive RGB colour space
- Printing devices use the subtractive CMYK colour space
- Colour spaces are always device dependent
- The perceptual CIE-Lab color space, which is device independent, is the all-encompassing reference colour space, defined by the http://www.color.org/
- Each device should be calibrated and profiled to obtain its input, display or output profile, the ICC profile
- An ICC profile simply means: "I'm so-so on greens, but my reds put lava to shame". It's a device-quirks-look-up-table, really
- With device profiles, the CMS, the Colour Management System of Win 7, OSX, Photoshop and others can convert between the colour spaces via CIE-Lab, but not all software has a CMS, though
- Maxwell Render takes care of gamma by applying inverse gamma internally and reapplies it on writing the final image, so the problem is not with "linear workflow" that plagues other 0.454545-renderers : )
So, one should, that's what I remember learning, go about it like this:
1. Calibrate the monitor(s), then profile the monitor(s) - often = ICC display profile for the monitor(s) (colour space quirks of the monitor)
2. Profile the printer, or obtain printing company's printer profile = ICC output profile for the printer (colour space quirks of the printer, which of course relates only to a certain paper stock and ink set)
3. Profile the digital camera = ICC input profile for the camera (for cameras outputting RAW, does not work for cameras outputting JPG)
4. Profile the scanner = ICC input profile for the scanner
5. Win 7: install all profiles in Color Management / OSX: install all profiles in Color Sync
Then, regarding Photoshop and other colour managed applications, one sets these preferences:
1. Working spaces RGB: ProPhoto RGB > Adobe RGB (1998) > sRGB / CMYK: ISO Coated V2 300% (ECI) for us on the continent : )
2. Color Management Policies RGB: Preserve Embedded Profiles (Why that? So one can work within the profile attached to the image one was given, although one's own setting is different) / CMYK: Preserve Embedded Profiles (Why that? Now you know)
3. However - under Convert to Profile, one can force an image to acquire a different profile, to convert an Adobe RGB image to a printable CMYK image, for example. This can be simulated via Proof Colors, which is a visual what-if scenario without actually converting (and messing up the image)
Why should one care?
1. If one now opens a photo or a scan (in Photoshop), that file's embedded ICC input profile is used by the graphics card, which uses the ICC display profile of the connected monitor, to display the file on the monitor's screen disregarding what one's working space is set to. That's how it should be
2. If one creates, draws, paints, sketches an image in Illustrator or Photoshop directly, one must attach a profile manually, depending on which colour space one wants to display or print it in
3. If one wants to print the image, one's own or the printing company's printer's driver, which uses the ICC output profile of the printer, prints the image as one has simulated it with Proof Colors and then, hopefully, converted it to the printer's colour space. If the printer has its own (different) CMS, it must be deactivated to not conflict with Photoshop's CMS
4. Again: to simulate, how an image will be printed, Photoshop allows on-screen soft proofing with Proof Colors, meaning to preview the image with the desired device's ICC output profile; e.g. for W3C standard (Safari and Firefox are colour managed) or a printing device (inkjet, laser, offset, younameit). It's more than a very good idea to retouch a rendering while soft-proofing is on for the desired display/printing intent
5. To keep in mind: CIE-Lab > scanner > camera > ProPhoto RGB > Adobe RGB (1998) > fancy inkjet > sRGB > offset printer CMYK > potato printing - the colour space, the gamut, becomes smaller from left to right
Now the issue...
When using Maxwell Render to generate an image,
Maxwell Render is the device, just like a camera or a scanner. One renders using Adobe RGB (1998) for the higher gamut compared to sRGB; one can always convert to the lesser colour space later anyways. When the rendering is done, the Maxwell Render device attaches the
ICC display profile to our file. Once opened in Photoshop, one can then operate on the image within that colour space and do whatever one fancies. But, alas, the image looks different opened in Photoshop than in Windows 7's slideshow, it looks different viewed in Chrome, it looks different previewed within Maxwell. How can that be? Simple for slideshow, Chrome, Word, and most applications:
many applications aren't colour managed, meaning:
they ignore a file's embedded ICC display profile and go about displaying images their own unfathomable ways. That's why offset printing from Word documents is not a good idea. Corporate Excel based photo databases? Down the drain with 'em. But what with Maxwell's own image preview and Justin's observation
on the very same monitor's screen?
Either, he has Photoshop set to not give a warning when opening files with a different ICC display profile to his Photoshop's Working Space setting and the image is converted upon opening it. Or, Maxwell Render's internal image preview has no proper CMS to display the ICC display profile selected for the rendering, meaning: it does not soft-proof the image properly, so to speak.
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