Expert explains FPS (Frames Per Second)

[VirusType2]

I was discusing FPS or frames per second with someone on the forum and felt that I would find out some more facts concerning the human eye and its perception of frames per second. Thought i would share that with you guys here in a new thread and also in order for that particular thread to stay on topic

What is the maximum number of frames per second the eye can register?
Peter Koch Jensen: I guess you mean how fast the images have to change in order for the human brain to perceive them as continuous motion. The flicker fusion frequency (caused by positive after images in the field of view) increases with the luminance and eccentricity in the field of view. A TV displays 60 half-images (NTSC in The USA) or 50 (PAL in Europe). This interlaced video frequency was invented for the exact purpose of smoothing out movements so they are perceived as continuous.

Do people’s ability to perceive images vary? And if so, how big can these differences be?

There can be quite large differences, depending on presentation, purpose, experience, motivation and alertness.


What is Hertz in computer monitor terms?

Morten Striboldt: Hertz (Hz) is the update frequency that the screen uses. On a monitor the images are drawn by an electron cannon that sends electrons at a fluorescent material that then lights up the screen. The images themselves are being drawn horizontally, line by line unlike a projector that updates the entire image at once. A screen with an update frequency of 60 Hz will therefore draw the image 60 times a second. This is not optimal, however, since the human eye can see these updates. You have to be at 72 Hz and above to perceive the image as steady (where the updates are too fast for the eye to see).

What is the definition of Frames per second in computer games?
FPS indicates the speed with which the graphics card can generate images and send them to the screen. 30 FPS therefore means that the graphics card can render 30 frames per second. A computer game running with 30 FPS can look quite ok, but it will seem imprecise as soon as the objects on screen start to move really fast. A regular DVD-movie also runs at 30 FPS and this seems quite natural, due to the motion blur technology which, in short, is a technique that generates a transition image between the real images.

In games you smooth out the motion by running it at 60 FPS, thereby making the motion more consistent and natural. The rule of thumb for FPS is, however, that a low and stable FPS is preferable over a high and irregular FPS. The latter will be registered by the eye and be perceived as jerky.


Those two things are interrelated. But how?

Since the human eye is limited as to how many images it can perceive per second, it ought to be unnecessary to play with more than 60 FPS. However, a higher FPS is preferable since the objects you see on screen will be more precise. If the graphics card generates 100 FPS for instance, an object that is situated at a given place at a given time will be more accurately depicted even though the screen only updates at 72 Hz.

If the screen only updated at 1 Hz, 100 FPS would still give a pretty good image of the moment (when the screen updated that is) as opposed to running at 1 FPS where you would have delay at up to one second.

This is what I understand so far:
Basically T.V. and video games display images differently. DVD's and broadcast T.V. displays Half images so the fps looks smoother. Computer generated graphics don't display half images the whole image changes. This doesn't decieve the eye the way watching t.v. does so a higher fps is required to replicate the smoothness and trick the eye into seeing it as seemless. However a lower framerate that is locked-in and steady is preffered over a higher framerate that drops. becuase the eye sees that drop in framerate and it looks jerky.

Source:
http://bf1942.boomtown.net/en_uk/articles/art.view.php?id=8643


EDIT: MORE INFO

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.

Source:
http://amo.net/NT/05-24-01FPS.html

 

[Warbie]

I'm not sure.

I do know that a low frame rate looks much worse on a monitor than it does on a standard tele (it's something to do with the way the images are displayed, and is why many console games look fine at 30 fps yet the same rate on a monitor looks like arse) and that anything below 60 on a monitor looks quite bad to me. Having a constant rate is also as important as a high one.

I found this part of your quote to be quite interesting:

'Do people’s ability to perceive images vary? And if so, how big can these differences be?

There can be quite large differences, depending on presentation, purpose, experience, motivation and alertness.'

This helps explain why some people sem to be happy with quite a low frame rate (my friend can play games in the 20's!) and others don't.

 

[destrukt]

lol @ the pc people complaining about 30fps on consoles/tv.

 

[VirusType2]

I'm not sure.

I do know that a low frame rate looks much worse on a monitor than it does on a standard tele (it's something to do with the way the images are displayed, and is why many console games look fine at 30 fps yet the same rate on a monitor looks like arse) and that anything below 60 on a monitor looks quite bad to me. Having a constant rate is also as important as a high one.

I found this part of your quote to be quite interesting:

'Do people’s ability to perceive images vary? And if so, how big can these differences be?

There can be quite large differences, depending on presentation, purpose, experience, motivation and alertness.'

This helps explain why some people sem to be happy with quite a low frame rate (my friend can play games in the 20's!) and others don't.

I agree right there, i find PC framerates disturbing and give me headaches at anything lower than about 30 and seriously prefer at least 60. If games could run at 72fps or 80fps at all times I couldn't ask for more.

The other thing about T.V. is that it displays a half image and it is very convincing to the eye. I have paused DVD before and caught this blur effect they use. its like an image with a blur .. transitioning into the next image. when the animation is in motion it looks smooth. DVD players use this motion blur technology. DVD's run at 30 fps. It is either not all players will pause on a half image or not all movies use this I don't know that off-hand.



It is the unsteady framerates and the drop in framerates that is so noticable on PC's becuase PC games rarely lock-in framerates. so it is Wild and fluctuates between about 20 and 80 which is highly noticable as jerky. Our eyes, our mind easily detects a change in framerate.

Console videogames usually lock the framerate so even if it is lower like 30 fps it looks fine and isn't even an issue. 60 fps looks better but you don't know any better becuase you have never seen it run at 60fps. It's like a pretty girlfriend. you think she is so hot and great looking untill she is standing next to a girl that looks twice that good.. (boy thats shallow) hehe





EDIT:
I came across this website and found parts of it just a little bit confusing but I understand most of the main points. There is alot of info in there but some of the questions he poses may have answers that may never be known.

He basically said things like "becuase of the way the eye works, its not so simple as fps, there are things like color, brightness, what part of the eye you see it with, even your mouse dpi effects how you percieve fps...

For example; when you look at a bright image, then close your eyes you still see the image. Thats called Afterimage, and makes motion in the movie theater appear more fluid, since the image is shined on a white screen.

I thought it was worth reading
check it out:
http://www.100fps.com/how_many_frames_can_humans_see.htm

If you find anything worth reading please give us a link

 

[Snakebyte]

I remember downloading a program that showed a split-screen view of rotating 3d blocks where you could change the fps of both sides to compare them. I remember I was able to tell the difference between 100s/200.

EDIT: I found it... I have no idea where I got it from, but I found it on my hard drive and uploaded it here:

http://www.zimstudios.com/ftm/fpscompare.zip

Remember that if you can't get it to go higher than ___ fps you'll have to disable vsync. It can go up to a max of 200fps.

 

[Top Secret]

I'll be the first to admit I can't tell the difference between 40 an 80 fps while staring at a monitor. But I swear on my life that I can *feel* it in the mouse.

 

[xcellerate]

i just hate the people who say, "there's no point in going higher than 60 fps because the human eye can't detect anything faster."

...and yes, i have heard it before.

 

[Warbie]

But I swear on my life that I can *feel* it in the mouse.

Certainly. When frames drop that low your accuracy will suffer. A frame rate dropping into the 40's can quite easily be the difference between winning or losing an encounter in a fps (especially online against decent opponents)

 

[Quixoticism]

http://www.zimstudios.com/ftm/fpscompare.zip

AWESOME! I get 7.2 FPS on this PoS Vaio.