Frames Per Second and the Human Eye

PersianImmortal · 13th September 2003, 9:00 PM

There are a lot of misconceptions about how many Frames Per Second (FPS) the human eye can perceive. I've seen arguments in these forums and other places where people say anything above 30 or 50 or even 60fps is a "waste", or isn't really noticeable. I guess these are all ways of justifying low framerates in games, but I found this article which explains this a bit more logically and factually Human Eye Frames Per Second. It's worth a read to clear up all the misconceptions.

Quote:

The overwhelming solution to a more realistic game play, or computer video has been to push the human eye past the misconception of only being able to perceive 30 FPS. Pushing the Human Eye past 30 FPS to 60 FPS and even 120 FPS is possible, ask the video card manufacturers, an eye doctor, or a Physiologist. We as humans CAN and DO see more than 60 frames a 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".

In terms of practical things we can do, I recommend that you:

- Make sure you use a refresh rate fix in WinXP so that your monitor runs at its maximum refresh rate and not 60Hz (which is terrible for the eyes). A good one for both Nvidia and ATI cards is Refresh Force.

- Set Vsync On. When Vsync is Off you may gain a few fps but the tearing is noticeable even on the best displays. This is because the monitor is limited in how many fps it can display at particular resolutions, so any higher and you're really seeing parts of images at 90fps for example, not the whole image.

- If there is a MaxFPS line in the ini file for your game then set it to your monitor's refresh rate. This seems to help reduce fps spikes and provide much less jerky/stuttery gameplay. By capping your FPS in the game engine to your refresh rate, along with Vsync on, you get less tearing but more importantly you get smoother fps. Setting a high MaxFPS is a placebo...it doesn't seem to improve performance as is often thought and in fact often results in more stuttering not caused by disk activity.

dcl · 13th September 2003, 9:37 PM

Good. It's what I've been saying all along.
Now hopefully this doesnt turn into a flame war..

It's been done too many times.

brembo · 13th September 2003, 10:33 PM

I see it as anything more than the refresh rate of your screen is useless.

eg. 150fps means nothing if your screen only refreshes 85 times a second.

PersianImmortal · 13th September 2003, 10:47 PM

That may well be true, but of course there is nothing stopping companies from developing monitors with higher refresh rates other than consumers who have no idea that (a) it is possible, and (b) that the human eye will benefit from those higher framerates.

I guess I made the post because I have read a lot of fallacies in virtually every thread comparing frames per second in a particular games. Someone will inevitably post "I only get 30fps, but the human eye can't see much above that anyway so everything else is a waste". I guess this is the "evidence" that yes, it does make a difference.

brembo · 13th September 2003, 10:54 PM

I think the whole 25-30fps thing came from television, which to my understanding uses a low frame rate and motion blurring to give the effect of fluent motion. After that, the notion of low fps stuck with people.

bees_man · 13th September 2003, 10:56 PM

but remember in quake 3 that u must get fps > 125 to get the extra jump height!!! the more fps the better i say!!!

SpeedRacer · 13th September 2003, 10:57 PM

I'm fairly certain any misconceptions about what the human eye can detect come from the decision for film to be recorded at 24fps, which was decided to be what humans can accept as being smooth motion for watching movies. Any less and you pick a less smooth motion.

However, I think this doesnt effectively relate to the environment computer games are played in.

Sure 24fps looks smooth but when your concentrating hard and fast action it makes sense to me that the brain is more active in processing its information and acting upon it (edit: comparing this to the neccesary brain activity required for watching a movie, which I would say is less because it doesnt require any reactions). There isnt a sampling rate of the human eye as far as I know that is precisely timed, so I think its largely linked to the amount of brain activity and demand for information needed to be processed.

This makes sense to me but its just my speculation.

I find the pursuit of a few fps to be incredibly redundant in games however. If your machine is churning out 40fps, squeezing it up to 50fps probably isnt going to change much (except a few bragging rights if thats what your after).

However what really should matter is whatever suits you for the enjoyment of the game your playing . . . because obviously your computer is feeding you enough information for your brain to be happy with how your playing the game isnt it?

Isnt this why we play computer games after all?

Wobbbz · 13th September 2003, 11:33 PM

I think speed racer is right...

I think... then again whtas goign on?

xtreme2k · 13th September 2003, 11:47 PM

The reason why 24fps seems smooth on a movie is because a movie frame is not the same as a computer generated frame.

A movie frame consist of motion blur. It is a CAPTURE of 1/24 second of MOTION. It has a thing called 'motion blur' in it while a CG frame does NOT have motion blur in it. That is why a 24fps MOVIE will seem a lot more smoother than a 24fps game.

Shinglor · 13th September 2003, 11:48 PM

Quote:

Originally posted by SpeedRacer
I find the pursuit of a few fps to be incredibly redundant in games however. If your machine is churning out 40fps, squeezing it up to 50fps probably isnt going to change much (except a few bragging rights if thats what your after).

What? 40 up to 50FPS is a great improvement.

I wish we had TV at 100FPS. They should've included it with the HDTV standard.

SpudBoy · 14th September 2003, 12:28 AM

nobody has actually found the maximum fps the human eye can see.

the american air force did some tests a while ago.

they found that their pilots could recognise still photos flashed at them (in a dark room and only for 1 frame) at around 150fps if i remember right.

the reason many people mistake the maximum fps an eye can see to be between 24 and 30fps is because of old films.

using a projector with rolling tape/film. images flashed in sequence blurred together at around 24 fps and appeared to be a smooth image.

i am not sure what the term for this is so i will make up a word

"photogenic decay"

basically our eyes "interpolate" between images so our brains can decifer fast moving objects.

there are huge amounts of information available on this subject around the web. the USAF is only one source.

PersianImmortal · 14th September 2003, 12:37 AM

The link I provide in the first post covers all of that including the Air Force tests:

Quote:

The USAF, in testing their pilots for visual response time, used a simple test to see if the pilots could distinguish small changes in light. In their experiment a picture of an aircraft was flashed on a screen in a dark room at 1/220th of a second. Pilots were consistently able to "see" the afterimage as well as identify the aircraft. This simple and specific situation not only proves the ability to percieve 1 image within 1/220 of a second, but the ability to interpret higher FPS.

SpudBoy · 14th September 2003, 12:38 AM

heh, sorry... didnt read your post very closely. i thought somebody would have already mentioned it.

Fodder · 14th September 2003, 7:00 AM

Sure, the pilots can notice a 1/220 image, but can they tell the difference between 1/220 and 1/110? Most people (forget the sillies who claim 30FPS is the max) claim not that you can't see higher FPS, but that it makes bugger all difference.

zebu · 14th September 2003, 7:08 AM

the other thing about film vs a game is that assume for a moment that you have 3 frames out of a movie. they contain a guy moving his hand from the top of the screen to the bottom. The first frame contains a perfectly still image of the mans hand at the top of the frame. its perfectly in focus and looks like a well taken still photograph. the last frame is the same perfectly in focus but at the bottom of the screen. the middle frame is a blurred mess as the hand was moving while the film was being exposed. this gives a sort of smoothing effect to the motion.

in a renered scene at the same number of frames per second of the same thing the top and bottom frames will be the same as with the film however the middle frame will also be perfectly in focus just with the hand half way between the top and bottom two. This gives you a much more choppy feel to the motion.

13th September 2003, 10:47 PM	#4
PersianImmortal Member Join Date: Jun 2001 Location: Canberra Posts: 6,375	That may well be true, but of course there is nothing stopping companies from developing monitors with higher refresh rates other than consumers who have no idea that (a) it is possible, and (b) that the human eye will benefit from those higher framerates. I guess I made the post because I have read a lot of fallacies in virtually every thread comparing frames per second in a particular games. Someone will inevitably post "I only get 30fps, but the human eye can't see much above that anyway so everything else is a waste". I guess this is the "evidence" that yes, it does make a difference. __________________ TweakGuides.com

13th September 2003, 10:56 PM	#6
bees_man Member Join Date: Feb 2003 Location: 4074 Posts: 1,801	but remember in quake 3 that u must get fps > 125 to get the extra jump height!!! the more fps the better i say!!! __________________ aka. Flagger

13th September 2003, 10:57 PM	#7
SpeedRacer Member Join Date: Sep 2001 Location: Sydney Posts: 2,928	I'm fairly certain any misconceptions about what the human eye can detect come from the decision for film to be recorded at 24fps, which was decided to be what humans can accept as being smooth motion for watching movies. Any less and you pick a less smooth motion. However, I think this doesnt effectively relate to the environment computer games are played in. Sure 24fps looks smooth but when your concentrating hard and fast action it makes sense to me that the brain is more active in processing its information and acting upon it (edit: comparing this to the neccesary brain activity required for watching a movie, which I would say is less because it doesnt require any reactions). There isnt a sampling rate of the human eye as far as I know that is precisely timed, so I think its largely linked to the amount of brain activity and demand for information needed to be processed. This makes sense to me but its just my speculation. I find the pursuit of a few fps to be incredibly redundant in games however. If your machine is churning out 40fps, squeezing it up to 50fps probably isnt going to change much (except a few bragging rights if thats what your after). However what really should matter is whatever suits you for the enjoyment of the game your playing . . . because obviously your computer is feeding you enough information for your brain to be happy with how your playing the game isnt it? Isnt this why we play computer games after all? __________________ Frangipani's on cars... Australia says NO!!! Last edited by SpeedRacer; 13th September 2003 at 11:00 PM.

13th September 2003, 9:37 PM	#2
dcl Member Join Date: Jan 2002 Location: melbourne Posts: 3,660	Good. It's what I've been saying all along. Now hopefully this doesnt turn into a flame war.. It's been done too many times.

13th September 2003, 10:33 PM	#3
brembo Member Join Date: Jan 2002 Location: Sydney Posts: 1,590	I see it as anything more than the refresh rate of your screen is useless. eg. 150fps means nothing if your screen only refreshes 85 times a second.

13th September 2003, 10:54 PM	#5
brembo Member Join Date: Jan 2002 Location: Sydney Posts: 1,590	I think the whole 25-30fps thing came from television, which to my understanding uses a low frame rate and motion blurring to give the effect of fluent motion. After that, the notion of low fps stuck with people.

13th September 2003, 11:33 PM	#8
Wobbbz Member Join Date: Jun 2003 Location: Perth Posts: 1,588	I think speed racer is right... I think... then again whtas goign on?

13th September 2003, 11:47 PM	#9
xtreme2k Member Join Date: Jun 2001 Location: Sydney Posts: 3,176	The reason why 24fps seems smooth on a movie is because a movie frame is not the same as a computer generated frame. A movie frame consist of motion blur. It is a CAPTURE of 1/24 second of MOTION. It has a thing called 'motion blur' in it while a CG frame does NOT have motion blur in it. That is why a 24fps MOVIE will seem a lot more smoother than a 24fps game.

14th September 2003, 7:00 AM	#14
Fodder (Banned or Deleted) Join Date: Dec 2001 Location: Sunny Melbourne Posts: 10,661	Sure, the pilots can notice a 1/220 image, but can they tell the difference between 1/220 and 1/110? Most people (forget the sillies who claim 30FPS is the max) claim not that you can't see higher FPS, but that it makes bugger all difference.

14th September 2003, 7:08 AM	#15
zebu Member Join Date: Jul 2001 Location: Albury Posts: 681	the other thing about film vs a game is that assume for a moment that you have 3 frames out of a movie. they contain a guy moving his hand from the top of the screen to the bottom. The first frame contains a perfectly still image of the mans hand at the top of the frame. its perfectly in focus and looks like a well taken still photograph. the last frame is the same perfectly in focus but at the bottom of the screen. the middle frame is a blurred mess as the hand was moving while the film was being exposed. this gives a sort of smoothing effect to the motion. in a renered scene at the same number of frames per second of the same thing the top and bottom frames will be the same as with the film however the middle frame will also be perfectly in focus just with the hand half way between the top and bottom two. This gives you a much more choppy feel to the motion.