Learning how to paint stratus clouds really comes in handy for those less dramatic yet dreary moods. Basically, when you see a cloudy day, you can rest assure that these clouds are up in the atmosphere!
A stratus cloud is basically a layer of fog that never hits the ground. Moreover, these clouds are uniform and do not bunch up together. That means it will exist as a monotone color across the landscape with no definite shape.
In terms of painting these clouds, it seems straight forward enough. Basically, just have to set a nice low intensity color and spread it across the digital canvas.
However, that'll be just too easy!
We will start off easy by using a base color. Although it seems rather trivial, it will get a bit more difficult in figuring out how these clouds affect the environment around it.
This is because of the relatively low altitudes of these clouds as it normally doesn't touch the ground. But what if there are objects on the ground that can reach where the clouds are?

Think about buildings and mountains. These objects extend far beyond ground level. As such, you will begin a canvas that has just basic shapes of these objects.
Make these objects dark and on a separate layer you can distinguish which layer has the correct objects.
Normally, if you have the small gradient of grey in your background, it can be considered done. However, you would probably want to create some form in the clouds to bring up more dynamic movements in your painting.
To do this, you will need to grab a small brush head and begin painting. Most of the time, I always tell you to concentrate on painting the light. However, we are going to paint the shadows in this case.

When you're done with that, it will look rough. To smoothen it out, use a round smudge brush. However, be careful of where you will smudge if your cloud painting.
That is, smudge in horizontal strokes rather than circular strokes.
This will create a layer type effects from the clouds.
So far, we have dealt with how to these clouds as an entity itself. However, that's only half the picture. Since these clouds are fairly close to the ground, it will shroud the objects in a fog-like atmosphere.
In this step, and you will be doing this often for painting those moody scenes, is to use the background to enhance the effects of these clouds.
That means you will need to work on how the background shapes interact with the stratus clouds by adjusting the color intensity from a dark grey to a lighter grey. However, make sure the grey in the mountains are still darker than the grey of the stratus clouds.

Besides making sure the grey is the right intensity in your digital painting. As objects become further away, the lighter it will become. This is to simulate how much air is building up in front of the objects based on the distance of the viewer from the objects.
In other words, you should reduce the color contrast of the background when your objects are near the horizon point.
The last step is creating depth with all the objects in the painting. This portion will require a bit of imagination and knowledge of depth.
In addition to creating the build up of atmosphere, you will also need to consider the visibility of the objects. As a general rule, objects in the background are less detailed and are often blurred out.
Now, depending on the focus, this is not always true in that you can have blurring effects focused on the foreground, the middle ground, or the background.

For this example, I've placed the focus at the foreground. When that happens, the mountains at the very back are blurred considerably. These mountains exist only as a visible hump.
Yet, the viewers know what they are regardless of the lack of details.
Basically, in 2d digital art, the main purpose behind learning how to paint stratus clouds is to give a sense of suggestion.
That is, this lesson should have taught you how to create a dreary mood and suggestion through color intensity using these clouds. Remember these important lessons as it is great foundation to build your knowledge on!
I hope you enjoyed this lesson and I look forward to seeing any artworks submitted in the site galleries!
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