An idea is born and the journey of a pixel begins. A single pixel will take on many forms until it finds its final resting place. Lets follow this pixel throughout its journey and watch the colour transformations it takes along the way.
Our pixel emerges from a dream as light is captured onto the camera’s sensor: R6, G84, B244 is born. For those of you who don’t speak RGB, it’s a beautiful, out-of-this-gamut blue. It’s one of those colours designers dream of and printers long for. This little pixel life has just begun, but it still has a long way to go.
Who is R6, G84, B244? Without anything tangible to assign to it, the values have no meaning. R6, G84, B244 needs a way to express itself and that vehicle to expression comes in the form of a colour space. We need to plot this colour; put a stick in the ground to give it a tangible value. The RGB colour space can come in a few flavours: sRGB, Adobe RGB or ProPhoto RGB.
The RGB colour space you decide on is based on a few factors. What is the intended final resting place for R6, G84, B244? If our pixel will never see anything other than the web, then sRGB makes sense. But, if we are planning on brighter and more saturated dreams for our pixel, then Adobe or ProPhoto will be better choices. Adobe RGB works very well for print (CMYK), and ProPhoto is a good choice for long-term archival and the latest generation of high gamut, multi-colour inkjet printers.
How do we translate from one language to another? It’s not by guessing, but by understanding where you are starting and having an accurate description of where you want to end up. In the case of languages, this is facilitated by a dictionary; in the case of colour conversions, we use ICC profiles to describe the starting place and the destination. Unfortunately, not all translations are exact; there are sacrifices in translations. If we give the application as much information as possible, then the losses are reduced.
Every colour conversion has two essential components: source and destination. In many cases, Adobe RGB is the source and USWebCoatedSWOP is the destination.
This is why it is so important to ensure that your RGB images have an embedded ICC profile. Without a source profile, the colour management module (CMM) will guess. Imagine if we had to guess when making language translations?
Now our pixel is growing up and needs to express itself; it needs a vehicle, and for this pixel, its vehicle is your monitor. But how does the monitor know how to display our R6, G84, B244? There are a few factors at play here. First is the colour space that our pixel resides in and the second is the ICC profile for the monitor. Without a monitor profile, our pixel would be just any other pixel. But with a monitor profile, we can properly display our little blue friend. Now that the video card and OS is armed with all the information, it sends the instructions to the monitor powering the RGB phosphors. The good news is this happens a lot faster than it takes to read this.
So pixel R6, G84, B244 is accurately displayed on screen, but are we done? The answer is yes if the monitor is all we hoped for from R6, G84, B244, but if this pixel is to see the light of day we need to continue down the road to where the ink hits paper.
We have a few options when it comes to making the conversion to CMYK. But before we go to the mode CMYK menu option, we need to determine the best flavour of CMYK. The first question that needs to be answered is: will the job be going on a sheetfed or web press? Next, is the paper coated or uncoated? Once you know the answer to these questions, you can select the appropriate profile and Photoshop has four ICC profiles that are tailored to the four options above: USSheetfedCoated.icc, USSheetfedUncoated.icc, USWebCoatedSWOP.icc and USWebUncoated.icc. Each of these are very good choices.
Now R6, G84, B244 has grown up and become Cyan 88 and Magenta 58 for a sheetfed coated press or Cyan 87 and Magenta 67 for a web press. As you can see, the profile you select has a big impact on the way our purple pixel ends up. Always be aware of the settings and options before you make that CMYK conversion.