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In my previous article (Human Eye Frames Per Second), I mentioned I'd have another to settle once and for all just how many frames per second our human eye is capable of seeing, so here we are.
If you havn't read my first article, do so now, it's quite lengthy, but worth your time in learning, plus it's enough foundation to start here.
Motion Blur is so important in movies and TV programming
In my first article, I mentioned how important motion blur is pertaining to frames per second. On Computers, this is essentially non-existant. Motion blur in movies, which run at 24 frames per second are designed for the big screen projector, which blasts movies to the screen, each frame in it's entirety in the widescreen format one frame at a time. Because each frame is filmed in a certain way, motion blur is used, meaning the frames are not perfectly clear, they contain blur.
The blur used in todays movies will eventually be replaced by completely digital movies (on very expensive screens, I should know, I worked with the technology at age 16), and with the advent of computer animation in movies, the process of replacing the blur on the film in movies is becoming more and more inevitable.
Computer's don't work this way (with blur that is), and essentially neither does anything digital. With digital, you either have an exact perfectly clear image, or an exact perfectly blur image like in movies. From the transition from movies to the TV, or DVD digital, an extra 4 frames are added each second in a method called frame mixing, just to match correctly the device it's being displayed on, your TV. NTSC(American) and PAL(european) use different kinds of TV formats, each with different refresh rates and resolutions. 640x480 for NTSC and 800x600 lines for PAL. With HDTV, everything is digital, and essentially 60 frames now, but most of these broadcasts use frame mixing, and until 2006 you won't need to trash your regular TV, though it may be a good idea now.
As many of you know, pause a DVD film movie during movement, or if you can a TV with your VCR and you'll see the blur (unless the image is static to begin with). Pause an animation DVD, or a cartoon on TV and you won't see the blur. Why is this so? Filmed movies, and Filmed TV shows work by bluring their subjects, actors, actresses, whatever. Filmed movies and TV are not taking a PERFECT snapshot image of the subject, each image is a blur, and a blur to the next giving the impression that everything is moving seemlessly (if nothing is moving in the scene, you can see a static image). In an animation or a cartoon, each frame or image of the 24/30 frames per second is perfect, there is no blur in the image - EVER.
I touched very breifly on AutoFocus Cameras, and even the best most expensive cameras not even coming close to matching the capabilities of our human eye in focusing. The professional cameras you see reporters with are capable of taking pictures of EXTREMELY fast moving objects in perfectly still quality at and above 1/4000 of a second. What does a camera being able to take 4000 pictures in a second prove?
Our infinitely seamless world.
Professional cameras can take perfectly still pictures without any blur, and like in the case of video cameras, pictures with blur. So where is the limit? How quick can we take a picture, and how slow can we take a picture? SLOW time progressed pictures have been taken, you've probably seem them at night where all the cars tail lights are in a streak. You've probably also seen the "Photo finish" camera's take the winning tell tale sign of a close horse race. What all of this really means is that unless we slow time, or speed it up, there isn't any blur in our world. That is of course unless you're drunk, the room is spinning, or you're on some LSD trip. Ok besides that.
Images in our world are infinitely streamed to us as I've said before. Living in this 3rd dimension as we do, our eyes able us to see depth/periphery, we can focus in very close, and as far as infinity. So is there really a limit to how many frames per second we can really see with our eyes?
Our limit, is there one?
Until someone proves me, all the scientists, optometrists, and the like wrong, there is no limit to how many frames per second our human eye can see. Theoretical limit yes, proven limit, NO.
Think for just a second how dumb it would be to push the limit on video displays, devices and the like if our eyes couldn't tell the difference between an HDTV and a plain old TV or a Computer monitor and a Plasma display. Ok, in that second how many times do you think your eye "framed" this screen? The number of times the screen refreshed? Nope, the number of times your eye streamed this page to you, it's a number that is potentially infinite, or at least until we understand the complexity of our own mind. Just know that this number is much, much higher than what your monitor is capable of currently displaying to you, that is matching your own interpretation.
Our Brain is smart enough however to "exact" 24 frames into motion, isn't it ignorant to say we can't distinguish 400, or even 4000 into motion? Heh the skies the limit, oh wait, then space...oh wait. Give us more, we notice the difference from 30-60, the difference from 60-120. It is possible the closer we get to our limit, be there one, the harder it is to get there, and there is a theory about this. Someone is across the room. Take one full step towards them. Now 1 half step towards them, then 1 half step of a half step, on and on until your 1 half of each movement you take. Will you ever get there? That my friend is open to debate, but in the mean time, will you take one step towards me?
The Human Eye perceiving 220 Frames Per second has been proven, game developers, video card manufacturers, and monitor manufacturers all admit they've only scratched the surface of Frames Per Second. With a high quality non-interlaced display (like plasma or a large LCD FPD) and a nice video card capable of HDTV resolution, you can today see well above 120 FPS with a matching refresh rate. With some refresh rates as high as 400Hz on some non-interlaced displays, that display is capable of 400 FPS alone. Without the refresh rate in the way, and the right hardware capable of such fast rendering (frame buffer), it is possible to display as cameras are possible of recording 44,000 Frames Per Second. Imagine just for a moment if your display device were to be strictly governed by the input it was receiving. This is the case with computer video cards and displays in a way with adjustable resolutions, color depth, and refresh rates.
Test your limit, you tell me...
Look at your TV, or ANY image device, then look at the device not looking at the image it is displaying, for example the TV itself, or the Monitor itself. Tell me the image on the screen is more clear, more presise than the image of the TV or the monitor itself. You can't, that's why the more frames per second, the better, and the closer to reality it really appears to us. With 3d holograms right around the corner, the FPS subject or maybe 3DFPS will become even more important.
The real limit is in the viewing device, not our eyes.
The real limits here are evidenced by the viewing device, not our eyes, we can consistently pick up the flicker to prove that point. In Movies the screen is larger than life, and each screen is drawn instantaneously by the projector, but that doesn't mean you can't see the dust or scratches on each frame. With NTSC and PAL/SECAM TV's, each line is drawn, piece by piece (odd, then even lines) for each frame and refreshes at the Hertz. The frames displaying because of this is exactly the hertz divided by 2 or (odd line 1 hertz then even line 1 hertz). Do a search for high-speed video cameras and you'll find some capable of 44,000+ frames per second, that should give you a clue.
CRT's be it PC monitors or TV's have to refresh with rates, known as the Hertz. Eye fatigue can happen because of the probe or line effect that happens after prolonged viewing, yes your eye sees this. Switch to your Periphery vision like I gave an example for in my first article and you can see the refresh rate. 60Hz and 50Hz also happens to be the frequency of the main power of the countries that use these Hertz in the TV refresh rates. Because of the way the technology works, by drawing each line individually, your Frame Rate/Refresh rate (not your FPS) is tied to your FPS. If something is running at 60 FPS however your monitor is at 60 Hertz and is interlaced, which TV's are locked at, you're seeing 30 Frames Per Second. However, if you have a nice computer monitor (NON-INTERLACED), and it's set to 120Hertz (72+ is considered "flicker free"), and your video is running at 120 Frames Per Second, you're seeing exactly 120 Frames Per Second. You may have heard that LCD's or Liquid Crystal Displays are "flicker free". LCD displays are capable of showing their FPS in a refresh rate, much like non-interlaced monitors are, example 75 Hertz is capable of 75 Frames Per Second. Technically, because an LCD pixel/transistors is either true or false, this technology is not only better, but faster than an electron gun on a phosphor like in a CRT, thus virtually eliminating flicker.
Technically speaking: NTSC has 525 scan lines repeated 29.97 times per second = 33.37 msec/frame or roughly 30 Frames Per Second at 60Hz BECAUSE it's INTERLACED.
Technically speaking: PAL has 625 scan lines repeated 25 times per second = 40 msec/frame or exactly 25 Frames Per Second at 50Hz BECAUSE it's INTERLACED.
So how does 60Hertz relate in HDTV's? Well, with progressive scanning (the XBOX supports this with it's NVidia GPU), each frame is drawn on each pass meaning 60Hz supports 60 Frames Per Second, but as you've learned although the hertz and FPS are related, the hertz of the display does not necessarily mean that it is the frames per second. Frames per second are determined by the display device and how it draws each frame. Normal TV's don't support progressive Scan and thus redraws half the screen on each pass, first draws the odd lines (interlaced), then the even = 30 Frames Per Second maximum.
As you've seen, it's not our human eyes, it's the display. More on this is the fact between interlaced and non-interlaced monitors. All computer CRT monitors are now made non-interlaced (and have been for quite some time), meaning the entire frame is refreshed at the refresh rate or Hertz. The frame is scanned all at once, thus the refresh rate can equal the Frames Per Second, but the Frames Per Second isn't going to go past the Refresh Rate because it's not possible on the display. Just because a video card is pushing 200 Frames Per Second, your display may be at 100Hz meaning it's only refreshing 100 times per second.
Thus, the big misconception that our eyes can only see 30 frames or 60 frames per second is purely due to the fact that the mainstream displays can only show this, not that our eyes can't see more. For the time being, the frames per second capable of any display device isn't even close to the phrase "more than meets the eye".
Definitions of relevance:
CRT Cathode Ray Tube - The tube or flat tube making up a TV which utilizes an electron gun to manipulate phosphors at the front of the tube for varying color.
NTSC originally developed in the United States by a committee called the National Television Standards Committee (525 lines).
PAL standing for Phase Alternate Lines (625 lines)
FPS - Frames Per Second - A Frame consists of an image completely drawn to a viewing device, example: Monitor
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Human Eye Frames Per Second
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