The amount of light that passes through the lens and reaches the digital sensor is called exposure.
So, exposure determines how much light or darkness will get to the sensor, and thus how light or dark the image will be when you take a photo. There are settings that are responsible for this: ISO, aperture, and shutter speed - which together are called "the exposure triangle."
Gouache paints come in many colors and are usually mixed with water to achieve the desired working properties and to control the opicity when dry, also like watercolor, gouache dries to a matte finish. it is similar to acrylic or oil paints in that is normally used in an opaque painting style
Oil paint, many figure, and hope this helps
