Ross, I think you need your own column...
Okay, here we go.
Figure 1 is a version of flats that contains empty areas. Figure 2 is a version of flats that contains no empty areas.
The first thing you'll notice is that the flats in Figure 1 have a lot of white space in it. Technically, it has a lot of empty space in it, but since it's transparent, it's showing the white background in the file. So right off the bat, I can guess that selections were made by using the Magic Wand tool to select empty areas in the lineart layer and then filled it on a separate layer with color. For some colorists, this is a perfectly acceptable way to receive flats. People that use the cut and grad style, for instance, would be okay with this I would think, but colorists that use a more painterly style would probably not find it very effective for them. The reason for that is that they often will use the smudge or blur tools to play around with things. The empty areas have no color for these tools to pull through when making a brush stroke, so it basically pulls an empty area into the colors. Here's an example of each.
In Figure 3, I've painted in a color. I intend to use the smudge tool to drag that color across his face from left to right. (Note: The color layer is under the lineart, so the lines won't be affected and won't affect the color one way or another.)
You'll notice in Figure 4 that the color dragged straight across with no interruption in the color. In Figure 5, I'll do the same thing to the pic using the flats with the empty area.
See the white area around his nostril? That's where the smudge tool is pulling empty space into the colored area that was there originally. (Again, it shows white because of the background, but there is really nothing there.) Having to work around multiple empty areas can quickly become a nightmare.
While I'm on the subject of the empty areas, another drawback to leaving those areas empty is what it does to the lineart itself. When the lineart is separated from the background it almost becomes dependant on the color underneath it to help bring out the lines. By leaving the empty areas in the flats/colors, it makes it difficult to see the lines. I'm not totally sure why, because it's easy to see them when there isn't any colors at all, so you would think it would work the same with colors there even if there were empty spots. Figure 6 shows the flats with the empty areas. At first glance, it doesn't look like a big deal, but take a look at the face of the guy underneath the brown werewolf and Ms. Anarchy's hair. The lines just aren't very black. Figure 7 shows it even better when I make the background transparent. Then Figure 8 is the flats with no empty spaces. Notice how those same areas look much more defined.
The other thing I want to point out with these two figures is the use of the brush tool and it's affects on flats. The whole purpose of flatting is to be able to come back later when you're ready to do the rendering and make quick selections of areas. The best way to do that is by using the Magic Wand tool. Simply click on a color and BAM!!!, instant selection. For the Magic Wand to work effectively it's best to have hard edged or "Aliased" flats.
Hand coloring areas of flats is fine. There is no harm in a little free-hand every now and then so long as you stay within the lines. =) The trouble comes in when you use the Brush tool to color in areas. The brush tool is anti-aliased, which is to say that it does not have a hard defined edge to it. It can be adjusted to have a nearly hard edge, but there will always be SOME blending of pixels at the edge. The pencil tool is aliased and is an excellent tool for free-handing some color in your flats. They are both located it the same area of the Photoshop tool bar (See Figure 9) and can be switched by right-clicking on the are and then left-clicking on the tool of choice.
Figures 10 and 11how the difference between the pencil tool and the brush tool.
Figure 12 shows how a selection with the Magic Wand tool would look when using the Brush tool. As you can see, there is still some work to do to get all of the blue area and remove the empty areas. (Note: The brush tool basically gives some cast-off, so even though you can't see the blue color in the white areas, Photoshop does, so it selects that area as well.)
Side Notes Regarding Flatting
Help out your colorist by trying to keep the file size down. Excessive layers cause the file size to grow and unless the colorist asks for each element on a separate layer, they probably don't need it that way. I can only speak for myself (so be sure to ask whoever you work for), but I'm generally pretty good with a single layer for my flats, a layer for my lineart, and a layer for my background. If I need to put things on a separate layer, it's not a difficult thing.
Unless your colorist specifically asks for (and provides you with) specific colors, it's generally accepted that a flatter is free to choose whatever colors they want, as long as (and here is the important part) the colors are separated. So if you want to put Superman in a pink cape, go for it. Just keep the elements separate. Greyscale is another good way to separate colors and also keep the file size down, so that's a double bonus right there. Again, communicate with your colorist and find out what he or she expects to receive back from you.
Do you really need to flat each window pane separately in that ultra-detailed picture? That depends on what your colorist wants. Most are okay with having that area just be done in a single color, and they'll either render it as a single shade or they'll separate it themselves later. Personally, when I do my flats I like to separate each element, so that means the window glass is going to end up a different color than the frame that holds it. It's more time consuming when I'm flatting, but it's going to help me out later on when I'm ready to start rendering. Be sure to ask what your colorist is expecting back from you (I'm sensing a theme) because if they're expecting a high level of separation and you give them something else, you're either going to be reworking it, or you won't be working for them again. Nothing is more frustrating than paying to have flats done for you and then having to do them yourself because what you got back didn't suit your needs. (I speak from experience on this one.) Suit your colorists needs at the right price and they'll keep coming back to you for work.
I'll be the first to admit it. I flat s-l-o-o-o-o-o-o-o-o-w. Part of that is because I do like to flat every detail separately, another reason is that I get distracted by the pretty lights of my TV. Let's face it, flatting doesn't pay a whole lot, so the key to the whole thing is volume. Flatting a page a day is going to earn you about $5 to $20 a day max. So increasing your rate of speed is important if you want to earn some pocket change. In my opinion flatters get their biggest payoff by the contacts they can make, and by the free hi-res lineart they receive that they can later practice on. As with anything though, the more you practice the better you'll get at it, so get yourself familiar with the tools in Photoshop and figure out where you can cut some corners. Saving certain Actions, or mapping certain keys to perform functions for you is a great way to save some time. Set goals for how long a page will take you and then time yourself. Pressure will do wonders for your speed. =)
That's it for now. I hope this helps. If anyone has any questions or comments feel free to let me know and I'll do my best to answer them. I might even get the answer right.
Ross, I think you need your own column...
I was about to nominate Ross for a column, myself. I see we're all in agreement.
Well...I suppose, if youys insist, then we should get his opinion.
We like him. We really like him!
lol it was my hideous attempt at flats that caused this whole tutorial! that's what i get for trying to help!
If it makes you feel any better, it wasn't just your flats that prompted me to write this. (I seriously appreciated the attempt to help me out though.) I've had terrible luck with flatters and I was going to make sure anyone else that worked directly for me read this and knew what I expected. Nothing worse that paying for flats and then having to do them yourself anyway because what you get back is a pain to work with. Live and learn.
As for the columns/blogs, I'll have to kick it around a bit. My schedule is pretty full right now between work/coloring/family, and I'm not sure I'd have enough to say to do something routinely on the subject. I'm still learning myself. I wouldn't mind throwing up some stuff every now and then, but I doubt you'd really be able to depend on me for consistent updates.
This is an honest man, ladies and gents. They're hard to come by these days, so look upon him well, and rejoice, for he has come among us!