# Persistence of Vision

**URL:** <https://boards.straightdope.com/t/persistence-of-vision/1022142>\
**Category:** Factual Questions\
**Created:** [August 16, 2025, 5:24pm UTC](https://boards.straightdope.com/t/persistence-of-vision/1022142 "2025-08-16T17:24:39Z")\
**Posts on this page:** 5\
**Page:** 2

<div class="post-metadata">

**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\
**Post date:** [September 19, 2025, 2:01pm UTC](https://boards.straightdope.com/t/persistence-of-vision/1022142/21 "2025-09-19T14:01:32Z")

</div>

Yes. There is a gearbox at the rotor.

---

<div class="post-metadata">

**Author:** ![pjd](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pjd/32/3009_2.png) [@pjd](https://boards.straightdope.com/u/pjd)\
**Post date:** [September 19, 2025, 2:06pm UTC](https://boards.straightdope.com/t/persistence-of-vision/1022142/22 "2025-09-19T14:06:37Z")

</div>

Ah, sneaky !

---

<div class="post-metadata">

**Author:** ![Jasmine](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jasmine/32/2964_2.png) [@Jasmine](https://boards.straightdope.com/u/Jasmine)\
**Post date:** [September 19, 2025, 2:57pm UTC](https://boards.straightdope.com/t/persistence-of-vision/1022142/23 "2025-09-19T14:57:18Z")

</div>

> [@Chefguy](#):
>
> Nailed it in one.

As usual! LOL

---

<div class="post-metadata">

**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\
**Post date:** [September 19, 2025, 5:03pm UTC](https://boards.straightdope.com/t/persistence-of-vision/1022142/24 "2025-09-19T17:03:49Z")

</div>

> [@Dereknocue67](#):
>
> It’s my understanding, this is called the stroboscopic effect. It’s an illusion that can happen when the object’s rotation speed is close to a multiple of the frame rate of the video camera _or_ the flickering frequency of the light source.

And in the days of CRT monitors and flourescent office lights it would give some people horrific headaches.

---

<div class="post-metadata">

**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\
**Post date:** [September 19, 2025, 5:28pm UTC](https://boards.straightdope.com/t/persistence-of-vision/1022142/25 "2025-09-19T17:28:32Z")

</div>

> [@Chronos](#):
>
> Yeah, incandescent bulbs take longer than 1/120 second to cool down, so they keep a more or less steady light output over the whole AC cycle.

Latency is a really neat aspect of lighting that, done well, is almost completely invisible. That fall time described, preceeded by a corresponding rise, is aesthetically pleasing or expected is a lot of applications and is artificially simulated. For example, motor vehicle turn indicator LED assbys sometimes introduce a little fade in/out to appear less strobey. You can also often see it in the familiar wigwag during a railroad crossing. Those recreating the hallmark exterior lamps on KITT/Knight Rider replicas have to think about this stuff.

Some devices use slow modulation to represent breathing or sleeping, sort of related.

[Previous page](https://boards.straightdope.com/t/persistence-of-vision/1022142.md?page=1)