Practical layer mask techniques useful for drawing will be introduced here.
 Using layer masks on fill layers
Using the layer mask, you can also paint like the example below using the fill layer.
First, prepare the line art.
For this example, the hair will be the subject to be painted.
① Click [Layer] palette→[New Layer Folder] to create a layer folder below the line art layer.
Enter the layer folder name as “Hair”.
② Select [Auto Select] tool→[Refer to all layers] and create a selection area based on the shape of hair.
Quick masks and selection layers are useful, when creating selections of small parts.
By using a quick mask and a selection layer, selection areas can be created and edited with normal drawing tools.
This technique can be used by selecting [Selection Area] menu → [Quick Mask] or [Convert to Selection Layer].
The painted area becomes the selection area, so it is useful for selecting small places that aren't completely enclosed.
③ Select the “Hair” folder, and select [Layer] menu→[Layer Mask]→[Mask Outside Selection].
A layer mask hiding the area outside the selection area is created in the folder.
④ While selecting the “Hair” folder, select [Layer] menu→[New Layer]→[Fill].
The [Select Color] dialog box will appear for choosing the color of the fill layer, so select the hair color and click [OK].
The color of the fill layer can be changed later, so choose any color.
The [Fill] layer of the selected color is created in the “Hair” folder and the layer mask of the folder hides the outside parts.
You can double click the thumbnail of the filled layer to display the [Select Color] dialog box and change the color of the fill layer.
⑤ Next, create a shadow fill layer for the hair color and select the layer mask.
Temporarily mask the entire layer by selecting [Edit] menu→[Clear].
⑥ Similarly, create several [Fill] layers with the colors used for shadows and highlights, and mask the entire layer.
⑦ Select the layer mask and color it with the [Brush] tool or [Airbrush] tool in the drawing color.
Whatever the chosen color at this time is, the color of the fill layer can be used to color, so there is no need to select a color.
⑧ The other parts were similarly colored with a fill layer and completed that way.
※Image material was used for the background.
The layers for the colored areas are shown below.
The skin was created by dividing the individual parts into folders.
When using the same color every time, such as for the skin, it is useful to register the layer folder in the [Material] palette.
 Using a layer mask for image materials, tonal correction layers and gradient layers etc.
The layer mask holds information between 0% to 100% (8bit, 256 steps of posterization)
Areas with 100% masking are completely hidden, and areas with 0% masking are fully visible.
In between 0% and 100%, the degree of masking depends on the posterization density.
You can use this to add posterization to image materials, tonal correction layers, gradation layers and so on.
It is effective when adjustments are needed after finishing painting, or to add information.
■Using it on image material layers
A layer mask was created on the image material layer “Mist (yellow)”, and only the hair was covered with that material.
The layer’s blending mode is set to [Glow Dodge].
The layer mask was created as follows.
After temporarily creating a mask based on the hair shape, adjustments are made with the [Watercolor] tool, taking the shadows into account.
Since the area to paste and the posterization information are held by the layer mask, the size of the material can be changed with the [Object] tool, and the material can be swapped repeatedly.
■Using it on tonal correction layers and gradient layers
In both tonal correction layers and gradient layers, layer effects can be controlled in detail by adding posterization to the layer mask.
The figure below is an example of pasting the tonal correction layer “hue/saturation/luminosity” and the gradient layer with the [Overlay] blending mode.
Although they are pasted on the hair area, the shadowed areas are adjusted so that the correction and gradation effects become weaker.
The mask is the same shape in both examples.
It looks like this when only the gradient layer is displayed.
The strength of the correction and the degree of the gradation of the tonal correction layer and gradient layer can be adjusted afterwards, so you can experiment with lots of effects easily.
■Using the posterization information of images
The posterization information of the layer mask is compatible with layers that have transparent posterization.
By using the selected area, drawing contents such as raster and vector layers can be converted to a layer mask.
Select the layer of the original image and select [Edit] menu→[Convert Brightness to Opacity].
The original image has been converted to transparency posterizations.
Select the layer converted to the transparency posterization, and click on the thumbnail of the [Layer] palette while pressing the [Ctrl] key to create the selection area.
* The selection area can also be created by holding the [Ctrl] key + clicking the thumbnail in the selection layer, quick mask and layer mask as well.
After that, select the layer to create a layer mask on, and create the layer mask using [Mask Selection] etc.
The figure below is an example of using a mask with a gradient layer utilizing multiple colors.
* For layers such as image material layers, tonal correction layers, fill layers and gradient layers, creating it newly when a selection is active will automatically create a layer mask.
■Using it in filtered images
Duplicate the layer of the original image and apply blur by using [Filter] → [Gaussian Blur].
By masking the face area of the layer that has the gaussian blur applied, it is possible to create an effect where the areas around the face are blurred.
The selection area can also be used to control the scope of the filter, but the advantage of the layer mask is that the masked area can be changed even after saving it.
Layer masks can be used in a lot of different ways by combining them with other layers. Have fun experimenting!