---
title: "How to add a threshold with Claude (tested prompt and ffmpeg command)"
description: "The serum bottle turns into a solid black silhouette on a white ground, with the backdrop's reflections cut into sharp black shards and no gray left anywhere. Install one skill and ask Claude Code, or run the ffmpeg command we tested yourself."
url: https://www.recharm.com/effects/threshold
---

# How to add a threshold with Claude

The serum bottle turns into a solid black silhouette on a white ground, with the backdrop's reflections cut into sharp black shards and no gray left anywhere.

Made by the command on this page, from our own test clip.

## Get this effect

1. ### Switch to Code in your [Claude Desktop App](https://claude.com/download)

2. ### Install the skill (once)

   ```
   Install the Recharm video effects skill: download https://recharm-growth-staging.s3.us-east-2.amazonaws.com/website/downloads/recharm-video-effects.zip and unzip it into ~/.claude/skills
   ```

3. ### Ask for the effect

   ```
   Add a threshold to input.mp4
   Brightness, on the clip's stored 0-255 luma scale, from which a pixel turns white: 186
   Blur radius before the cut, so grain doesn't break the edges into speckles: 2
   ```

## Several videos, several effects, one ask

Put your clips in the folder, mention them with @, and ask for everything at once. Claude runs one tested script after another on each clip, then joins them.

Add a threshold to **@clip1.mp4**, put a sale badge on **@clip2.mp4**, give **@clip3.mp4** a VHS look, then join all three with crossfades.

## Settings you can change

Ask Claude to change any of these, or edit them at the top of the command.

| Setting     | Default | What it does                                                                                                                                                     |
| ----------- | ------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `THRESHOLD` | `186`   | Brightness, on the clip's stored 0-255 luma scale, from which a pixel turns white. Raise it for more black; this footage is bright, so small changes move a lot. |
| `SMOOTH`    | `2`     | Blur radius before the cut, so grain doesn't break the edges into speckles. 0 turns it off.                                                                      |

## Without the skill

Don’t want to install the skill? Paste this prompt into Claude Code and Claude writes the command itself.

```
Apply a threshold effect to the whole of input.mp4 so every pixel is either pure black or pure white. First blur each frame slightly (Gaussian blur, sigma 2) so grain doesn't turn into speckles, then make every pixel whose luma value (as stored in the video, 0-255) is 186 or higher pure white (255) and every other pixel pure black (0), with no color left. Use ffmpeg; no text is drawn, but if you add any, draw it with Pillow, not ffmpeg's drawtext. Keep the size, length (6 seconds) and audio, output 30fps H.264 yuv420p, and save it as output.mp4.
```

## Run it without Claude

This is the exact command we tested. Save it as `threshold.sh` and run:

```
sh threshold.sh input.mp4 output.mp4
```

```
#!/bin/sh
# Threshold: turn every pixel pure black or pure white, so the shot becomes a stark stencil of flat shapes.
# Usage: sh threshold.sh input.mp4 output.mp4
# Needs ffmpeg.
set -e
IN="$1"; OUT="$2"
THRESHOLD=186   # brightness (the clip's stored luma, 0-255) from which a pixel turns white; raise it for more black
SMOOTH=2        # blur radius before the cut, so grain doesn't break the edges into speckles; 0 turns it off

# Blur slightly, then set the brightness to 0 or 255 and the color to neutral gray.
ffmpeg -y -i "$IN" -vf "gblur=sigma=$SMOOTH,lutyuv=y='if(gte(val,$THRESHOLD),255,0)':u=128:v=128" \
  -r 30 -c:v libx264 -crf 16 -pix_fmt yuv420p -c:a copy "$OUT"
```

## More stylize and art

- [Anime style **Anime style**](https://www.recharm.com/effects/anime-style)
- [ASCII art **ASCII art**](https://www.recharm.com/effects/ascii-art)
- [Blueprint **Blueprint**](https://www.recharm.com/effects/blueprint)
- [Charcoal drawing **Charcoal drawing**](https://www.recharm.com/effects/charcoal-drawing)
- [Claymation style **Claymation style**](https://www.recharm.com/effects/claymation-style)

## Find 3x _winning ads_

Recharm cuts your ad footage into tagged, searchable clips: hooks, testimonials, product shots. Find the shots that win, add the effect with Claude, and ship 3x more ad edits.

[Start 14-day free trial](https://www.recharm.com/get-started)