I was wondering what the various Blend Modes did, and so I thought I would share the answer. The topic is likely too deep for this tutorial and I'm sure will be covered by other lessons, but I wanted to share the link so that folks could bookmark it for future reference. I'll paste that information as an answer in the hope it helps someone else in the future.
The Blender manual for v2.8 is still incomplete, so looking up Blend Modes or Color Blend Modes refers you to the GIMP documentation on Layer Modes. The GIMP docs are very detailed and even give the math formulas used for each mode. I've pasted the common modes from those descriptions (minus the math formulas) but there are a few Blender modes that don't directly correspond are still missing. I'll first give the link, and then what I have so far (and maybe better descriptions can eventually be included in the Blender docs):
GIMP page:
https://docs.gimp.org/en/gimp-concepts-layer-modes.html
Mix -
Darken - compares each component of each pixel in the upper layer with the corresponding one in the lower layer and uses the smaller value in the resulting image. Completely white layers have no effect on the final image and completely black layers result in a black image.
Multiply - mode multiplies the pixel values of the upper layer with those of the layer below it and then divides the result by 255. The result is usually a darker image. If either layer is white, the resulting image is the same as the other layer (1 * I = I). If either layer is black, the resulting image is completely black (0 * I = 0).
Color Burn - inverts the pixel value of the lower layer, multiplies it by 256, divides that by one plus the pixel value of the upper layer, then inverts the result. It tends to make the image darker, somewhat similar to “Multiply” mode.
In photography, burning is a technique used in a darkroom to increase the exposure in particular areas of the image. This brings out details in the highlights. When used for this purpose, burn may work best on Grayscale images and with a painting tool, rather than as a layer mode.
Linear Burn -
Lighten - compares each component of each pixel in the upper layer with the corresponding one in the lower layer and uses the larger value in the resulting image. Completely black layers have no effect on the final image and completely white layers result in a white image.
Screen - inverts the values of each of the visible pixels in the two layers of the image. (That is, it subtracts each of them from 255.) Then it multiplies them together, divides by 255 and inverts this value again. The resulting image is usually brighter, and sometimes “washed out” in appearance. The exceptions to this are a black layer, which does not change the other layer, and a white layer, which results in a white image. Darker colors in the image appear to be more transparent.
Color Dodge - multiplies the pixel value of the lower layer by 256, then divides that by the inverse of the pixel value of the top layer. The resulting image is usually lighter, but some colors may be inverted. In photography, dodging is a technique used in a darkroom to decrease the exposure in particular areas of the image. This brings out details in the shadows. When used for this purpose, dodge may work best on Grayscale images and with a painting tool, rather than as a layer mode.
Add - The pixel values of the upper and lower layers are added to each other. The resulting image is usually lighter. The equation can result in color values greater than 255, so some of the light colors may be set to the maximum value of 255.
Overlay - inverts the pixel value of the lower layer, multiplies it by two times the pixel value of the upper layer, adds that to the original pixel value of the lower layer, divides by 255, and then multiplies by the pixel value of the original lower layer and divides by 255 again. It darkens the image, but not as much as with “Multiply” mode.
Soft Light - not related to “Hard light” in anything but the name, but it does tend to make the edges softer and the colors not so bright. It is similar to “Overlay” mode. In some versions of GIMP, “Overlay” mode and “Soft light” mode are identical.
Hard Light - the equation consists of two parts, one for darker colors and one for brighter colors. If the pixel color of the upper layer is greater than 128, the layers are combined according to the first formula shown below. Otherwise, the pixel values of the upper and lower layers are multiplied together and multiplied by two, then divided by 256. You might use this mode to combine two photographs and obtain bright colors and sharp edges.
Vivid Light -
Linear Light -
Pin Light -
Difference - subtracts the pixel value of the upper layer from that of the lower layer and then takes the absolute value of the result. No matter what the original two layers look like, the result looks rather odd. You can use it to invert elements of an image.
Exclusion -
Subtract - subtracts the pixel values of the upper layer from the pixel values of the lower layer. The resulting image is normally darker. You might get a lot of black or near-black in the resulting image. The equation can result in negative color values, so some of the dark colors may be set to the minimum value of 0.
Hue - uses the hue of the upper layer and the saturation and value of the lower layer to form the resulting image. However, if the saturation of the upper layer is zero, the hue is taken from the lower layer, too.
Saturation - uses the saturation of the upper layer and the hue and value of the lower layer to form the resulting image.
Color - uses the hue and saturation of the upper layer and the value of the lower layer to form the resulting image.
Luminosity – (same as GIMP Value mode?) uses the hue and saturation of the upper layer and the value of the lower layer to form the resulting image.
Erase Alpha -
Add Alpha -
No problem, I just pasted it from the docs. I actually needed a break from texture painting these wooden boards. I'm glad you made the reference to the great Bob Ross for this video. Much like watching Bob Ross paint, I go through all of the same motions that you do - yet my creations turn out NOTHING like yours! Your "happy little accidents" look great, while mine tend to look like a combination of an oil spill and a fatal train wreck! You make it look way too easy.... LOL I was going through all of the Blend Modes to try to find a way to fix the mess I created. Nothing helped my wooden boards, but I learned a lot (which I guess was the point of this exercise).
