How To Use Composite Modes to Enhance Light Leak Effects. May 18 2013
Light leaks are a simple way to add a gorgeous, distinctive aesthetic to video projects.
When using light leaks you simply select the leak you like, layer it over your footage and change the composite mode to your desired one - which 99.9% of the time is Screen mode.
Now, what about all those other composite effects that we mostly ignore?
The term compositing refers to the blending or merging of two video tracks to create a new image, it is this new image that has been composited from the original two.
To keep this guide most effective, examples of each composite mode will consist of two reference images.
Note - Keep in mind with composite effects, the layer ordering may or may not be important. Certain composite modes will behave differently depending on which image is on top.
Before reading the below descriptions of each composite mode watch this video to see the different modes in action.
Normal is the default composite mode for clips.
When a clip uses normal composite modes you can still adjust its transparency by changing its opacity parameter. When doing so the whole transparency across all colours and shades of light and dark will be affected equally.
AddAdd composite mode examines the colour values in every overlapping pixel and adds them together.
The finished composite will always be lighter than either of the two original clips. As a result this mode typically suits darker original images, as light images which add up to produce absolute white can impose upon the boundaries of broadcast limits.
SubtractSubtract is used to darken all overlapping colors.
Foreground whites go black, while background whites invert the overlapping colour value creating a negative effect in the foreground image.
Foreground blacks become transparent, while background blacks are preserved.
Mid-range colors are darkened or inverted depending on whether the background image is lighter or darker than the foreground.
The order in which you layer your two clips is important as you will get different results both ways.
DifferenceDifference composite mode works by subtracting color values from the clip on V1 from the color values of the clip on V2. This mode is fantastic if you’re looking to capture the ‘psychedelic’ look from the 60’s.
This effect works better with really colourful light leak overlays.
MultiplyMultiply accentuates the darkest parts of each overlapping image.
Progressively lighter parts of overlapping images become increasingly translucent, allowing whichever image is darker to show through. Absolute white is completely transparent.
Blacks in both images are preserved.
This effect works well to highlight light areas of the frame, or to make the background image only viewable in the lighter parts of foreground image (the light leak).
The order of layers does not matter.
ScreenThis is the most commonly used composite mode for light leaks. It gives best results for people chasing the classic light leak look.
Screen emphasises the lightest parts in the foreground image.
Colors in the overlapping layer become transparent as they get darker. Black is completely transparent.
Whites from both layers show through in the resulting composite.
Screen mode is very useful for when you want the foreground image mixed with the background, based solely on its brightness. This is why it is the go mode for light leak effects.
OverlayThis mode applies two different techniques, it does a little bit of multiply and a little bit of screen.
If the color value in foreground image is lighter than middle gray, 128 value, then screen mode is applied.
If the color value is lower than 128, multiply mode is applied.
The visible result is that darker colors in the background image intensify overlapping areas in the foreground image, while lighter colors wash out overlapping areas in foreground.
This means the composited image contains more light, more dark and more contrast.
The order of clips in overlay mode is important.
Hard LightHard light compares the color values of the clips that are light and makes them even lighter, while the areas that are dark get even darker. This produces a hard edge between the light and dark areas. A simple way to understand this effect is to think of a spotlight. What is in a spotlight is overly bright, what is outside goes dark.
The Soft Light composite mode is similar to the Hard Light mode only in this instance the lighting effect is soft or diffused producing a softer transition between light and dark. Lighter areas of the image will stay light too.
The order of two clips affected by Soft Light composite mode is important.
This is a great mode for tinting the background image with the colors of the foreground image, in our case, tinting the background with the colors found in our light leak effects.
Darken emphasises the darkest parts of each layer. Whites in either image allow overlapping image to show through completely. Lighter parts of overlapping image become translucent while darker parts of image remain solid and retain detail.
Put simply, the color values of each pixel from each clip is compared and the argument is won by the darker pixel.
LightenThe opposite to the Darken composite effect.
Lighten compares the color values of each clip and selects to show the lighter of the two.
So there you have it, the various composite modes explained!
As you can see there are a great many modes that can have a really striking impact on the aesthetic of your production.
Now go out there and stray from your usual composite mode (I'm guessing it's mainly screen!) and experiment.
Try layering more than one light leak effect at a time and assigning each layer a different composite mode - the results can be amazing.
I hope you enjoyed this article, and it helped to clarify the different composite modes.
If you got use out of it please share with the social buttons below so that others may do the same :)
Charlie @ LightLeakLove