Complexity of Color: proofing for print

If you haven't read parts one and two about color, it might be a good idea before proceeding with this post. (Man, they were posted last April; I've been a slacker...)

We're talking about the process required for getting the image captured by a camera to be accurately portrayed on a printed page of a book or magazine. We're not concerned at the moment with color reproduction of a photograph. We've seen that the range of colors we can see with our eyes is different than that which can be reproduced by a computer monitor or a printed page. These ranges are represented by the following image:



where the total color blob (a technical term) represents what we see with our eyes, the triangle represents what colors a monitor can reproduce, and the rounded triangle represents the color range that can be reproduced by the four color process printing method.
So...you've have your image digitized and the files converted to cmyk. Now, how do you know what your printed image will end up looking like without the expense of actually making plates and starting up a printing press? (Which, by the way, is done, but mostly when the printing is being done in Asia and/or the printed piece is very color critical.)
This is where the color proof comes in. During the course of a designer putting together a book cover or interior pages that print in color, he and others working with him have seen various preliminary proofs: on their monitor, from a color copy, or from an ink jet printer. The colors viewed on these various mediums will vary for a variety of reasons: is the monitor color calibrated? Are you looking at color copier toner or ink from an ink jet printer on the paper? what kind of paper is the copy being made on? This is one stage of the proofing process that can be "dangerous". Something may look brilliant on your monitor, but flat when printed with toner on a color copier. Or you may like the color copy and show it off, fully expecting that that will be what you will see when the piece is printed. It's almost enough to make one long for the old days...before desktop publishing. Way back then, ten years or so, film houses actually output film after scanning an image. Actually, they output 4 pieces of film (remember cmyk?) to make a proof. A proof made from the actual film that would be used to make the plates would be a very accurate representation of what would be printed on a press. It would have the actual dots:


like this. Of course normally the dots are not visible because they're much smaller.
Now, with the digital age, the printing press still prints with dots, but the proof you're likely to see probably won't contain dots. It (the proof) will most likely be output from a proofing device like an ink jet printer, only a very expensive ink jet printer made to simulate the color you can expect once the job goes on press. The key word there is "simulate". It's not an exact match because it's not made using the dots that will be used on the press. So why not get get the old style proofs made from film? Some companies still do on special jobs. The truth is that film proofs are just too expensive and time consuming. As the digital proofing systems evolve, they get better and better and less expensive.
Oh, and just to make it more interesting, unless you have a viewing booth with color balanced lighting to view your proofs in, you're probably looking at them under florescent lights, which tend to give a green cast to everything. Remember, at some point, pleasing color is subjective...
There's a vast expanse of information on proofing you can find on the Net, but I hope this gives you a little insight into some of the process.