Note: This 3-part blog post series is now complete!
As you will recall from our first post in the series, blending modes are the various ways that different layers and brushstrokes can be applied. We discuss them using three simple terms: base pixels, blend pixels, and result pixels.
Base pixels are the pixels on the next layer below the current one when you’re blending layers, or the pixels that are being painted over when using a brush tool. Blend pixels are the pixels that you’re painting, or the pixels that exist on the layer with the blend mode applied. Result pixels are what you wind up seeing after Photoshop has computed how the various blend layers will interact – your final result.
We covered the first half of the available blend modes in Part 1, which predominantly affect the brightness and contrast of your image, with a few exceptions that don’t fit anywhere else such as Dissolve. Part 3 (coming soon) will round out the explanation of the various modes, and dig into how best to use them.
The blending modes we’re going to be looking at today tend to deal more with occlusion and colour changes, which makes them very useful for digital artists and compositors.
Overlay is one of the more useful blending modes, especially if you’re working on a composite image piece. This is because Overlay is actually a combination of two of the other more useful blending modes, Screen and Multiply. If your blend pixels are dark, it functions like Multiply, and if your blend pixels are light, it functions like Screen. The base pixels don’t get replaced, but instead get mixed with your blend pixels to create a pleasing composite (with a bit of careful tweaking).
This blend mode is also like a combination of two other modes, in this case of Colour Dodge and Colour Burn. Blend pixels that are lighter result in a dodged area, and blend pixels that are darker result in a burned area. Pure black and pure white as blend pixels don’t create pure black or pure white as a result pixel, just brighter or darker areas.
Hard light is essentially a more potent version of Soft Light, with a more pronounced contrast-enhancing effect. With this mode, pure black or pure white blend pixels create pure black or pure white result pixels, so a gentle touch is often the best course of action.
Vivid light is very similar to hard light, except that it also creates a large increase in the saturation of your base pixels as well as dramatically enhancing contrast. Sometimes, the two are indistinguishable.
I often wonder how these names were chosen – what would ‘non-linear light’ be, Adobe? Anyways, the linear light blending mode works in a similar method to a combination of linear dodge and linear burn, which brightens or darkens the image by adjusting brightness instead of contrast.
This is another useful blend mode for compositors and heavy editors, since it replaces base pixels with blend pixels, depending on the brightness of the blend pixels. If the blend pixels are lighter than 50% grey, darker base pixels are replaced. If the blend pixels are darker than 50% grey, lighter base pixels are replaced. It can be a bit confusing, but hopefully the image will help!
It’s a bit hard to see when this would be a useful effect to use, but nevertheless, it’s been in Photoshop for decades. RGB values for each blend pixel are added to the RGB values of the corresponding base pixel. As we know, RGB is measured between 0 – 255, and in this case if the sum of each colour channel is more than 255 it is converted to 255, and if it is less than 255 it is converted to 0. This makes every channel either pure red, pure green, pure blue, pure black, or pure white – though again, who knows why you’d want to.
This is probably one of the most overused and abused of Photoshop’s blending modes, thanks in no small part to the ‘Difference Clouds’ filter and legions of people with Photoshop trial versions. This one is a bit complex to explain, but playing around with it makes its results fairly clear. Colour values for each channel on both blend and base pixels are compared, and the value of the darker pixel is subtracted from the value of the brighter pixel. White creates a total inversion, and black does nothing at all.
Exclusion is simply a version of Difference with less contrast. Sometimes I suspect that the Adobe engineers just enjoyed playing with the mathematics, and didn’t really consider why it would be necessary to include these at all.
Subtract & Divide
These two modes are as self-explanatory as they are useless: Subtract subtracts the blend colour value from the base colour value, and Divide divides the two.
(Subtract on the left, divide on the right)
This mode is actually starting to get back into the realm of utility. It combines the luminosity and saturation values of the base pixel with the hue value of the blend pixel.
Similar to Hue, this combines the hue and luminosity values of the base pixel with the saturation value of the blend pixel.
To round out the series, this mode combines the hue and saturation values of the base pixel with the luminosity value of the blend pixel.
This mode retains the luminosity of the base pixel and combines with the hue and saturation value of the blend pixel. This makes it particularly useful for colouring black and white photos or tinting photos to a certain colour.
Lighter Color & Darker Color
These two modes are similar to Lighten and Darken, except that they compare the colour values of the base and blend pixels, and display whichever is lighter or darker, respectively.
(Lighter color on the left, darker colour on the right)
So as it turns out, we don’t need 3 parts just to finish explaining the various modes, but to round out part 3 we’ll highlight which blending modes will be the most useful in your work. You’ll probably have noticed by now that some of them seem completely useless (looking at you, Hard Mix!), but some are incredibly powerful tools that can take a lot of the hard work out of the image compositing that is essential for the digital photography artist.
Note: This 3-part blog post series is now complete!