Art Tip: Light Theory (Patreon)

Based on the private lesson I did with Ennuix (Lab Manager tier), here's a breakdown of the components of lighting and shadows.

1. Light
The areas impacted by the main light, and noticeably bouncing off light. This area tends to be a little lighter in colour than the actual colour of the object.

2. Midtone
The areas illuminated by some light, but is not significantly bouncing off light. This is the area from which we identify the colour of the object. 

3. Shadow
The areas that are not impacted by the main light, usually a darker colour of the midtone. Sometimes I separate this further into mid shadows and dark shadows. 

4. Ambient Occlusion
Smaller areas that aren't impacted by any light.
These are usually nooks and crannies, like the armpit or crotch area. It can also occur where two objects are touching, like Adrian's hand against the bed there.

5. Drop Shadow
Basically the same as shadow, but specifically shadows that appear due to objects obstructing the light, instead of surfaces facing away from the light. 

6. Specular Highlight
The concentrated reflection of light within the light-impacted area. This is usually more noticeable on shiny and darker-coloured objects, especially hair or wet skin. On the other hand, it might be very faint or even totally absent on dull objects like cloth or unpolished wood.

7. Fill Light
Light that are not from the main light source, specifically that comes from the environment. The blue light from the sky on a sunny day is a common example of fill light.
In Photography, Fill light is usually an actual lamp that is obscured with a screen to diffuse the light.

8. Bounce Light
Light from the main light source that is bounced off of another object. Very similar in concept to the Fill light (sometimes they're even grouped together), this can be light bouncing off of the walls, the floor, or any nearby object.
The colour of Bounce Light depends on what object it bounced from. For example, the bounce light on Adrian's abs is light beige, because of the colour of the bed sheet. If the bed sheet was red, the bounce light would also be red.

9. Rim Light
An area of Light that forms an outline, usually coming from behind the subject at a certain angle.
This is more of a tool for artists (and photographers) to use, for the sake of framing the subject and making them "pop" against the background.

10. Sub-surface Scattering
Usually most applicable to skin, this is when light partially penetrates the translucent layers of the skin, and is scattered into a (usually) more vivid colour.  You can easily see it when you place a finger on a lit flashlight. It can also be seen under strong sunlight or a strong studio spotlight 

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When it comes to actually applying the theory, you don't have to put all 10 concepts into practice. Most artists simplify the process to only include 3-6 of the concepts.

In general, having only Midtone, Shadow, and Ambient Occlusion is enough to make great art. But, the option is there if you want to experiment and find a lighting style that fits your vision.

For example, the fourth pic above, my personal preference is to simplify it to Midtone, Shadow, Specular Highlights, and Rim light, creating an eye-catchingly shiny but simple rendering style.

ADDENDUM: 11. Bloom

Bloom is an effect when a high-intensity light hits an object and causes a faint halo to form around it, i.e. the light is blooming around the object

Note how the bloom is not just forming around the blue light, but also around the light areas of his skin, as well as the reflection on the gold ring.

In digital art, you can achieve this effect by either manually airbrushing the bloom on, OR you can select the areas hit by light, copy it into a new layer, and apply a gaussian blur until it looks like a bloom.

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Feel free to contact me in the Art Labs channels on Discord if you have any questions!