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Blend Modes

Popular Blend Mode Examples

Mixing things up is the spice of life quite literally imagine if chicken could only ever taste of chicken, fortunately, we can blend flavours and come up with concoctions that tickle the taste buds.

In the world of video, blending modes can do the same for our images so in this article we are going to take a look at blending modes and what they can do for your projects. Without understanding blending modes they just become a novelty that we use on an ad hoc basis with a little understanding they can become a powerful tool we can use to alter the looks of our images for some really cool looks.

Blending modes also known as compositing modes seem to be a magical mystery. Blending modes aren’t magic they’re mathematical equations. That use the numerical values of the pixels in an image to determine how pixels of one image mix with the pixels of another image to create a new composite image. The new image is the result of the blend.

Normal

Now that we know how blending modes work let’s take a look at what the most common blending modes are. The most obvious blending mode is the normal blending mode which is the normal composition of your images.

Normal Blend Mode = Original Image

The Math

In this mode, the Merge offers an extra Subtractive/Additive control which lets you select between additive and subtractive compositing or even make a mix between these types. The two formulas of the Normal mode are:
Result Color = Background Color ∗ (1 − Foreground Alpha ∗ Alpha Gain ∗ (1 − Burn In)) + Foreground Color – for additive
Result Color = Background Color ∗ (1 − Foreground Alpha ∗ Alpha Gain ∗ (1 − Burn In)) + Foreground Color ∗ Foreground Alpha ∗ Alpha Gain – for subtractive
As you can see, the difference between the additive and subtractive formulas is that in the additive one, the foreground doesn’t get multiplied by its Alpha.
This is because additive compositing implies that your images are already pre-multiplied by Alpha. It normally means that completely transparent areas are black and 0 in Alpha corresponds to 0, 0, 0 in R, G, B.
The additive approach is used in 3D and professional compositing software.

The subtractive approach is mostly used in editing software, Adobe-ware and other programs working in low colour depth. It works with “un-premultiplied” or pre-divided by Alpha images (depending on the way the Alpha was created).
In such images, the colour extends beyond object edges and in semi-transparent areas, it has the same values as in completely opaque ones. The multiplication by Alpha is performed on the fly at the time of putting the layers together, as you can see from the subtractive formula.
A benefit of this workflow is that all the colour tools operate the values unaffected by transparency (straight colours), so highlights remain highlights and shadows remain shadows regardless of how transparent or blurred the object is.
In software like Fusion, which is capable of processing the images in 32 bit per channel mode, it’s easily fixed with pre-dividing by Alpha (sometimes strangely called un-premultiplying), but in 8-bit or 16-bit integer mode you will experience colour distortions after performing sequential divisions and multiplications due to rounding losses.

Fusion supports both modes as it’s capable of working in multiple colour depth.

Multiply

Multiply is one of the most common blending modes It multiplies the colour of the blend layer by the colour of the base layer Resulting in a darker image with multiply black remains black and white doesn’t show up.

Result Color = Background Colour ∗ Foreground Colour

This mode is used to composite shadows, apply lighting maps and masks.
In the areas where the Foreground Color is 1, the Background Color remains unaffected. If the Foreground Color is 0, the result is black.

Multiply Blend Mode

Screen

Screen is the opposite of multiply it multiplies the inverse of the blend layer by the inverse of the base layer and results in a brighter image With screen white appears as white and black doesn’t show up. Screen is useful if you want it to appear that your blend is projected on your base.

Result Color = Foreground Colour + Background Colour − Foreground Colour ∗ Background Colour
or
Result Color = 1 − (1 − Background Colour) ∗ (1 − Foreground Colour)

Screen is essentially, inverted Multiply. You can clearly see it from the second version of the formula, where the colours of both layers get inverted and then multiplied together.
This mode is used, for example, to combine reflection and transparency on the glass.
The result is never more than 1.

Screen Blend Mode

Add

Add is very similar to screen but as opposed to multiplying the inverse it adds the colour value of the blend layer with the colour value of the base layer always resulting in a lighter colour. It is a great option if you want to light something up. If you want to add smoke to a shot you can shoot smoke in front of a black screen Make your smoke footage the blend layer and set your blend mode to add, you now have smoke in your shot.

As you can conclude from the Additive formula of the Normal mode, if you set the Alpha Gain = 0 in the Merge and leave the Subtractive/Additive = 1 by default, you will get a pure addition of the Background and Foreground colour. The Foreground Alpha is completely ignored in this case.

Here is what happening if we substitute Alpha Gain by 0 in the formula:
Result Colour = Background Colour ∗ (1 − Foreground Alpha ∗ Alpha Gain ∗ (1 − Burn In)) + Foreground Colour


Result Color = Background Colour ∗ (1 − Foreground Alpha ∗ 0 ∗ (1 − Burn In)) + Foreground Colour

Result Color = Background Colour ∗ (1 − 0) + Foreground Colour

If you set Burn-In = 1, the resulting colour will be a pure addition too, but the Foreground Alpha will be also added to the Background Alpha. Most of the time it’s undesirable because adding two images with Alpha together, you will get Alpha > 1 (Alpha = 2 in completely opaque areas).

But there is a case when such handling of the alpha is preferable. Imagine, that you separate your image onto two layers by cutting a part of it with a mask to process it separately. If you merge it back over the original in the Normal mode, you will get a semi-transparent border of the mask in the resulting image. This is because in the default Normal mode you first multiply the Background Color with inverted Foreground Alpha when you cut a part of the image and then do it again while pasting it on top.

Why not leave the background layer intact while cutting a part of it as a foreground? Good question – simple answer: semi-transparent areas will reduce transparency twice and mix the original colour with an altered one.

Add Blend Mode

Subtract as you would guess does the opposite of add, It subtract the value of the blend layer from the base resulting in a darker image. Black appears transparent.

Subtract Mode

Overlay is one of the most interesting modes the blend layer looks at the pixels in the base layer If a colour value of the base pixels is above 50% The blend pixels will screen and if the colour value of the base pixels is below 50% The blend pixels will multiply.

Overlay Blend Mode

These are just a selection of the blending modes but there a good foundation of starting off with your projects.

Timeline Showing Gradient Base for Subtract Blend Mode.

Photographers use gradient filters to create effects we can do the same with blend modes. The photographer would use a glass gradient tobacco filter where we can use a jpeg gradient image With a gradient of orange-brown that ramps down to white. You can place the gradient above your image in the timeline and change the blending mode to multiply, adjust its opacity to get the colour you want.

We can make a soft dreamy scene by duplicating the image on the timeline having one image above each other. The image on the bottom will be the base and the image on the top will be the blend we will work on the blend image. On the blend image, we can apply a blur and then change its blend mode to Screen. Again you can adjust the opacity to suit your needs and there you have a nice dreamy image.

Original
Blur / Screen Blend Mode

Blending modes are powerful when used right they have the potential to give you looks that never seemed possible. Start off by writing down formulas and recipes that you found that work for you combined with clips and ingredients that you’ve saved within those looks. Soon you’ll have a catalogue that you can whip out and throw in the blender whenever you need.