First of all I'd like to say that your art is awesome.
Second, I'm happy to find another Open canvas user, so I can help in some bits.
About layer masks, I don't really know much about it so i don't think I can help you with that question. But in terms of the color and blending, there are a couple techniques.
First, it's important that you have a sense of color theory i.e. what shades go where, does this area need reflective light, how much contrast there should be in certain areas, etc.etc. Of course, this varies from person to person, style to style, genre to genre, so forth and so on. But since you already pointed out an example, I think we can work from there.
ok to get this type of light gradiation, there's a couple ways of going about it in open canvas. I use Open canvas version three but the basic tools I use are in 4 as well. (the only feature I can think of that's new in 4 that may pertain to this gradiation coloring is the different brush settings).
In the pen window, for every brush tool, you have the option to adjust the size and center thickness through the two main bars. You'd probably know this. There are 5 sizes/center thicknesses you can save. You can click the tabs to change between sizes. An easier way to shift between these saved tabs is merely pressing the hotkeys e and r. It's pretty useful to set up the tabs from smallest to largest. (it'll seem similar to the hotkeys of [ and ] in photoshop, but unfortunately there are only 5 usuable states).
For the watercolor brush tool specifically, there are a couple things you can tweak to get the right type of blending methods. The #1 thing you'd like to tweak would be the opacity bar:
Note: When blending with the watercolor brush tool, the layer you add your gradients on works best on the same layer as the flat colors. However, if you don't want to ruin your flat colors and wish to work on another layer, there are also ways to work with that as well, which I will explain later.
Lighter blending calls for low opacity, strong blending calls for high opacity. There are also 3 bars on the pen window that are used specifically for the watercolor tool:
The first bar adjusts how much the initial color that you painted on effects the blend of the entire brush stroke. If all bars are at 0, and you had a foreground color of red and painted a brush stroke across a white background, you'd get a thick brush stroke (1). If the first bar is at 100, and all other bars are at 0, you'd get a brush stroke with softer, more opaque edges at the beginning and end (2). Adjust the 3rd bar and you get longer blending times. With bar 1 at 100, bar 2 at 0, and bar 3 at 50, a more gradient look occurs (3). The greater the value of the 3rd bar, the longer the stroke must be to attain the initial foreground color. This is a brush stroke at (bar 1:100, bar 2:0, bar 3:100) (4). The second bar is a surrounding color blender, much similar to blending tool in photoshop. At (0,50,0), it looks like a blend between the initial red and white background(5). At (0,100,0), the tool scarcely shows the initial color and becomes more like a blending tool(6).
Actually, it's so much so a blender that even if your initial color was black, a straight stroke at (0,100,0) through these two rectangles of red and orange would still yield a blend from the stroke, practically unaffected by the black(7). And you'd think, 'yay, now I know how to blend!' but there are some pitfalls from this method. When trying to blend certain colors together such as red and green, a dark blend will occur, which, more often then not, you'll not like (8). The problem is that there's too many colors in between the spectrum (orange,yellow) and interrupts the blend. The only way avoid this situation is either to place the colors inbetween manually (9) or place a middle color inbetween (10). After understanding these rules, this method works well enough for blending.
Another method is to create an alternate layer. At (0,0,0) a watercolor brush stroke blends well enough(11). However if bar one or bar two have adjustments, then the white background of the layer its on forms (12 at (100,0,50) and 13 at (0,100,50)) However this can be salvaged by changing the layer to multiple (14 and 15 have same stats as 12 and 13 on different layers).
If you don't want to use the watercolor brush to blend, you can always use the airbrush tool (my personal prefernce for blending). I usually use the airbrush tool at a very light opacity (5%), but you can adjust to your needs. Here's a stroke of pink across peach on 5% opacity (16). Again this effect can be applied on either the same color layer or seperate color layers. If you want to use straight gradient blends, you can use the gradient tool. Select a specific area to gradient, choose the background and foreground colors, and go for it (17). The gradient will go from foreground color to background, so know your direction. If you want to use a seperate layer for the gradient tool, you will need to have your background color the same as the canvas color(or the same color of whatever layer you're working with). Otherwise it'll come out with whatever colors you used for fore/background colors(18). However, if you used white as a background color, you can still use this gradient. Change the layer to a multiple layer and the following gradient will occur (19). However, it's kind of a guess on how the foreground color will blend with the background, so adjust accordingly. If the gradients on a seperate layer seem they need to be lightened, you can adjust the layer opacity. (20) and (21) and (18) and (19) respectively, at 50% layer opacity. Again, adjust accordingly.
So for practice let's try working on that one previous piece you posted up by Hoden Eizo.
Here I just made the lightest color the background color and you can gradient the blush on as you please. I tried to put the blush back on without reference by just using the airbrush tool, but I don't think I did too well ^^;;
1.
2.
I have 2 ways of posting the colors for this particular piece. They both look about the same, so depending on how you want the layers arranged, you can set it up as such. One is either to make the blush layer a multiple layer and put it above the original. The second way is to make the original layer a multiple layer and then make the blush a standard layer below it.
just for fun I tried messing with layer masks. They have some interesting capabilities, but unfortunately, i had no idea what i was doing. sorry. :\
blegh I'm tired now -_-;; hope that helps.
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