---
title: Effects
description: The effects over every Undertone picture, each with its own settings, and how to add a random one.
url: https://mpdreamz.github.io/undertone/pictures/effects
---

# Effects
Effects go over every picture, whatever its style and tonality. Any number can be on at once, each with its own
settings, on the **Effects** page of **Settings…**, which draws each one over the picture showing now.
![The Effects page: the vignette and grain on, each with its slider and a picture of it](https://mpdreamz.github.io/undertone/images/shots/app/settings-effects.png)
Out of the box two are on: a **vignette** that darkens the corners a little, and a subtle **grain**. The others are
off until you turn them on.
They apply in a fixed order, so no effect undoes another: glass and halftone (which both read the picture somewhere
else), the vignette, bloom, posterize, paper, the light leak, dither, and grain last.

| Effect     | Settings                                                                  |
|------------|---------------------------------------------------------------------------|
| Vignette   | Strength, 0 to 3 (1 is the usual; dark pictures get more than light ones) |
| Grain      | Amount, 0 to 0.12 (0.035 subtle, 0.06 strong)                             |
| Dither     | Levels per colour, 2 to 16; cell size, 1 to 4 points                      |
| Halftone   | Spacing between dots, 4 to 24 points; the grid's angle                    |
| Glass      | Flute width, 12 to 96 points; how much each flute magnifies               |
| Bloom      | How bright a part must be to glow; strength                               |
| Light leak | Strength; warmth, from rose to amber                                      |
| Paper      | Strength                                                                  |
| Posterize  | Bands of lightness, 3 to 16                                               |

Each example below is the same aurora picture at the effect's default settings, dark on the left and light on the
right.

## Dither

Ordered (Bayer) dithering to four levels per channel, in cells a point across: the look of an old screen or a risograph. Grain is left off, which would blur the pattern.

| Dark                                                                                                     | Light                                                                                                      |
|----------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------|
| ![Dither over aurora, dark](https://mpdreamz.github.io/undertone/images/shots/effects/dither-dark-1.png) | ![Dither over aurora, light](https://mpdreamz.github.io/undertone/images/shots/effects/dither-light-1.png) |


## Halftone

A grid of dots at 45°, about 8 points apart, each the colour of the picture under it and bigger the further that colour is from the base: print, up close.

| Dark                                                                                                         | Light                                                                                                          |
|--------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------|
| ![Halftone over aurora, dark](https://mpdreamz.github.io/undertone/images/shots/effects/halftone-dark-1.jpg) | ![Halftone over aurora, light](https://mpdreamz.github.io/undertone/images/shots/effects/halftone-light-1.jpg) |


## Glass

Reeded glass in front of the picture: vertical flutes about 36 points wide, each showing a magnified slice of what is behind it, lit along one edge.

| Dark                                                                                                   | Light                                                                                                    |
|--------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------|
| ![Glass over aurora, dark](https://mpdreamz.github.io/undertone/images/shots/effects/glass-dark-1.jpg) | ![Glass over aurora, light](https://mpdreamz.github.io/undertone/images/shots/effects/glass-light-1.jpg) |


## Bloom

On a dark picture the bright parts glow into the dark around them; on a light one, the colours soften and bleed, like a lens with a little haze.

| Dark                                                                                                   | Light                                                                                                    |
|--------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------|
| ![Bloom over aurora, dark](https://mpdreamz.github.io/undertone/images/shots/effects/bloom-dark-1.jpg) | ![Bloom over aurora, light](https://mpdreamz.github.io/undertone/images/shots/effects/bloom-light-1.jpg) |


## Light leak

A warm film light leak from the left or right edge, at a height that changes with the picture: screened over a dark picture, a warm tint over a light one.

| Dark                                                                                                       | Light                                                                                                        |
|------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------|
| ![Light leak over aurora, dark](https://mpdreamz.github.io/undertone/images/shots/effects/leak-dark-1.jpg) | ![Light leak over aurora, light](https://mpdreamz.github.io/undertone/images/shots/effects/leak-light-1.jpg) |


## Paper

Mottled paper fibres and the odd speck under the colour, as if the picture were printed on handmade paper.

| Dark                                                                                                   | Light                                                                                                    |
|--------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------|
| ![Paper over aurora, dark](https://mpdreamz.github.io/undertone/images/shots/effects/paper-dark-1.jpg) | ![Paper over aurora, light](https://mpdreamz.github.io/undertone/images/shots/effects/paper-light-1.jpg) |


## Posterize

Hard bands of lightness instead of smooth gradients, the colour kept: a screen print. Light pictures get narrower bands, so they keep their shapes.

| Dark                                                                                                           | Light                                                                                                            |
|----------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------|
| ![Posterize over aurora, dark](https://mpdreamz.github.io/undertone/images/shots/effects/posterize-dark-1.jpg) | ![Posterize over aurora, light](https://mpdreamz.github.io/undertone/images/shots/effects/posterize-light-1.jpg) |


## A random effect on each shuffle

**Add a random effect on each shuffle**, on the Effects page, adds one more effect to every new picture: a different
one each time, at its default settings, chosen from those you leave checked and that are not already on. It is off
until you turn it on.

## In the config file

Every effect has its own section in the [config file](https://mpdreamz.github.io/undertone/reference/configuration); `on` turns it on or off and
keeps its settings:
```toml
[effects]
random = false
random_never = ["dither"]

[effects.grain]
on = true
amount = 0.035

[effects.halftone]
on = true
spacing = 12
angle = 45
```

`undertone render --effect halftone --effect leak` draws effects from the command line (`--effect` can be given more
than once); `undertone effects` lists them.