I’m a newbie to ColorThink Pro and am excited by its potential in helping me as an educator in the classroom to better explain Colour Management theory - a picture is worth a thousand words, right?!
I’ve been having the below discussion with Pat from Tech Support and he suggested I take it to the forum as it may be helpful to others so I’ll try to summarise what I’m trying to achieve below and then leave it open for others to chime in if they choose:
Basically, I have an image I want to use for a class exercise which I think demonstrates the power of rendering intents within colour management quite nicely. I’d love to show the image here in this post (for clarity) but can’t see how to do it apart from a link to it from somewhere else, sorry. The image is basically a stylised picture of Lana Del Rey’s face (all solid colours) with a floral pattern running through the background and the skin areas. It was created in Photoshop as RGB. There’s essentially only 5 colours used (though the anti-aliased edges produce a lot more colours in the total image):
- 27.192.38 (dark green background)
- 15.222.30 (bright green pattern in background)
- 213.255.69 (olive skin)
- 160.217.1 (darker skin pattern)
- 0.0.0 (Black face contour and hair)
When the image is viewed in RGB, the colours are clearly visually different from each other, but when you print them to a CMYK device, using Relative rendering intent, the two greens almost sit on top of each other at the edge of the CMYK gamut and the results are that the floral pattern in the background almost completely disappears - a great teaching moment then arises! ;-D
I then want to use ColorThink Pro to import the image and compare it against the AdobeRGB source profile and the desitination Xerox Color 1000 Press profile. I then want to use the vectors function to show how the colours will move when the various rendering intents are set.
However, I’m not quite seeing what I’m expecting. According to my understanding of how the Relative and Perceptual intents work:
With Relative RI, out of gamut colours (eg. RGB) are supposed to stop (clipped) at the outer edge of the smaller gamut (eg. CMYK) and inner gamut colours move according to the white point. I’m seeing this nicely in the 3D grapher.
Regarding Perceptual, this intent maps the whole source gamut to fit the destination gamut. This means that even in-gamut colours can be moved closer to the neutral point and become less saturated as the outer edges of the source gamut fits to the destination gamut edge (I kinda think of it as a balloon being shrunk down to the smaller size).
So, considering this with regards to my training image: The #2 RGB green colour (15.222.30) is not fully saturated so it’s a fair distance in from the edge of the AdobeRGB gamut. When using Perceptual RI, this colour should then be mapped INSIDE the destination CMYK gamut, not to the edge of the CMYK gamut, right?
The CTPro 3D grapher is showing the colours stopping at the edge of the CMYK gamut, which doesn’t seem right.
So either my RI theory is wrong or the CTPro 3D graph is wrong… Maybe Im looking at it too much in terms of the shapes of the gamuts, instead of actual Lab values when colours convert from one gamut to another…
Either way, I’d love to know what’s going on so I can use this image in my teaching exercise and properly explain how it’s all working to my students.
Your help is MOST welcomed and appreciated!