# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/DYCrTVzAbRW
- **Gondola URL:** https://gondola.cc/posts/65199736-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/e97009a5e8.jpg
- **Posted:** 2026-05-07T15:06:41.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

Pulse Width Modulation (PWM) controls LED brightness by rapidly switching the LED ON and OFF. A 50% duty cycle means the LED is ON half the time and OFF half the time. Electrically, that is half the average power.

But visually? It does not look half as bright.

Human brightness perception follows a roughly logarithmic or power-law response. Our eyes are far more sensitive to changes in darker tones than brighter ones. That means linear PWM steps produce non-linear perceived brightness.

Example:

* 10% PWM duty cycle does not look “10% bright”
* 50% duty cycle does not look “half bright”
* Most of the visible brightness change gets compressed toward the upper PWM range

This is where gamma correction matters.

Gamma correction remaps brightness values so that equal numerical steps produce visually smoother brightness transitions.

Instead of:
Input → PWM directly

You use:
Input → Gamma curve → PWM output

Typical approximation:
Output = Input^γ

Where gamma (γ) is often around:

* 2.2 for displays
* ~2.0–2.8 depending on LED applications and perception targets

What this means in practice:

* A visually “50% bright” LED may only need ~20–25% actual PWM duty cycle
* Lower brightness levels need much finer resolution
* Without correction, fades look abrupt at low levels and compressed at high levels

This becomes critical in:

* LED matrices
* RGB lighting
* Display backlights
* Automotive lighting
* POV displays
* Embedded UI systems
* Smart home lighting
* Stage lighting
* Camera-facing LEDs

It also explains why cheap LED dimmers often look terrible:
They use linear PWM tables.

Good lighting systems use:

* Gamma lookup tables (LUTs)
* Perceptual dimming curves
* High bit-depth PWM
* Temporal dithering
* Hybrid current + PWM control

There’s another layer too:
LED optical output itself is not perfectly linear with current, and display systems often stack multiple transfer functions together:

* Sensor response
* Signal encoding
* Display gamma
* Human perception

That entire pipeline is engineered around perception, not raw physics.

#STEM #Electronics #ElectricalEngineering #EmbeddedSystems #LED

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## Tags

led, electronics, stem, embeddedsystems, electricalengineering

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