> While people have an image frame rate of around 15-20 images per second to make moving pictures appear seamless,

This is just...wrong? Human vision is much fast and more sensitive than we give it credit for. e.g. Humans can discern PWM frequencies up to many thousands of Hz. https://www.youtube.com/watch?v=Sb_7uN7sfTw

▲

nandomrumber 4 hours ago | parent | next [-]

NO YOU ARE!

> make moving pictures appear seamless

True enough.

NTSC is 30fps, while PAL is 25fps.

The overwhelming majority of people were happy enough to spend, what, billions on screens and displays capable of displaying motion picture in those formats.

That there is evidence that most(?) people are able to sense high frequency PWM signals doesn’t make the claim that 15 to 20 frames per second is sufficient to make moving pictures appear seamless.

I’ve walked in to rooms where the LED lighting looks fine to me, and the person I was with has stopped, said “nope” and turned around and walked out, because to them the PWM driver LED lighting makes the room look illuminated by night club strobe lighting.

That doesn’t invalidate my experience.

▲

toast0 an hour ago | parent [-]

> NTSC is 30fps, while PAL is 25fps.

That's not really right. Most NTSC content is either 60 fields per second with independent fields (video camera sourced) or 24 frames per second with 3:2 pulldown (film sourced). It's pretty rare to have content that's actually 30 frames per second broken into even and odd fields. Early video game systems ran essentially 60p @ half the lines; they would put out all even or all odd fields, so there wasn't interlacing.

If you deinterlace 60i content with a lot of motion to 30p by just combining two adjacent fields, it typically looks awful, because each field is an independent sample. Works fine enough with low motion though.

PAL is similar, although 24 fps films were often shown at 25 fps to avoid jitter of showing most frames as two fields but two frames per second as three fields.

I think most people find 24 fps film motion acceptable (although classical film projection generally shows each frame two or three times, so it's 48/72 Hz with updates at 24 fps), but a lot of people can tell a difference between 'film look' and 'tv look' at 50/60 fields (or frames) per second.

▲

cubefox an hour ago | parent [-]

Any idea why movies are still mostly at 24 FPS? Is it just because people became used to it?

▲

pwg 7 minutes ago | parent | next [-]

Because movies (in film form) are projected an entire frame at a time instead of scanned a line (well, actually a dot moving in a line) at a time onto the screen. I read somewhere (but no longer have the link) that when projecting the entire frame at once as film projectors do lower frame rates are not as noticeable. I do not know if modern digital projectors continue to project "whole frames at once" on screen.

▲

toast0 44 minutes ago | parent | prev [-]

Most (or at least many) people visually recognize 24 fps content as film and higher frame rate content as TV/video.

Filmmakers generally like their films to look like film and high frame rate films are rare and get mixed reviews.

Some TV shows are recorded and presented in 24 fps to appear more cinematic (Stargate: SG1 is an example)

	▲	cubefox 35 minutes ago \| parent [-]
		That association seems to be an unfortunate equilibrium because higher frame rates seem to be "objectively" better, similar to higher resolution and color. (Someone without prior experience with TV/movies would presumably always prefer a version with higher frame rate.)

▲

Gitechnolo 37 minutes ago | parent | prev | next [-]

The discussion on flicker fusion frequency (FFF) and human vs. canine perception is fascinating. When building systems that synchronize with human physiology, like the metabolic digital twins I'm currently developing, we often find that 'perceived' seamlessness is highly variable based on cognitive load and environmental light.

While 24-30fps might suffice for basic motion, the biological impact of refresh rates on eye strain (especially for neurodivergent users) is a real engineering challenge. This is why I've been pushing for WCAG 2.1 AAA standards in my latest project; it’s not just about 'seeing' the image, but about minimizing the neurological stress of the interaction itself.

▲

zacmps 4 hours ago | parent | prev [-]

Badly phrased but not wrong, this is the minimum frame rate for humans to perceive motion as supposed to a slide show of images.

The maximum frame rate we can perceive is much higher, for regular video it's probably somewhere around 400-800.

	▲	Gigachad an hour ago \| parent [-]
		Maximum depends on what it is you are seeing. If it’s a white screen with a single frame of black, you can see that at incredibly high frame rates. But if you took a 400fps and a 450fps video, I don’t think you would be able to pick which is which.