Dr0idWhisperer
Android Enthusiast
The concept that there is a maximum possible FPS beyond which the human eye can't distinguish any real difference is not entirely accurate. For more details, see this article and this article among the many which refute this claim. In particular the common claim that "The human eye can't see more than 24 (or 25 or 30 or 60) FPS" is completely false, and is partly borne of the misconception that TV or movie FPS is the same as PC game FPS, and partly possibly borne out of a need to justify lower frame-rates.
It's true that movies and TV only use around 24, 25 or 30 FPS, depending on which part of the world you're in. But there are three important differences between Movies, TV and PC games:
1. Movies and TV use Motion Blur, so that if at any time you freeze a movie scene on your DVD player for example, a large part of the scene may consist of blurred objects. Furthermore, the images in a movie or on TV do not have crisp detailed outlines. In a PC game on the other hand, if you take a screenshot or pause the game at any time, you will notice that everything is usually extremely sharp and distinct regardless of how fast it was moving when the shot was taken. Take a look at the screenshot comparison above: on the left is a fast motion shot of an alien from the movie Alien vs. Predator, on the right a fast motion shot of an alien from the old game Alien vs. Predator 2. Thus 24 often-blurred frames from a movie wind up looking much smoother to the human eye than 24 or even 30 distinct frames from a fast-moving PC game. So why can't games use motion blur? Well indeed most recent games have started incorporating blur effects. This can definitely help to reduce the visible impact of lower frame-rates, but aside from the fact that not all games have motion blur, the next point addresses why this doesn't always work. Even with motion blur, the graphics in PC games may still have very sharp outlines which only settings like Anti-aliasing can smooth out, but ironically this usually come at the expense of further lowering FPS.
2. Control responsiveness steps in again to further differentiate between a movie and a game. In a movie or TV show, the viewpoint is not under your control; it is typically a static or smoothly panning camera. In a game however, your control over the viewpoint means that in a rapidly moving gaming at 24 or even 30FPS you will notice the general choppiness due to a lack of responsiveness. The variability of control responsiveness based on variable frame-rate also helps highlight the next point below.
3. PC games do not have a rock-solid unchanging frame-rate, while TV and movies do. While some games have a frame-rate cap of 30 or 60 FPS, very few if any PC games can be locked down to consistently show exactly 24 or 30 FPS - their FPS will vary, sometimes significantly. Movies and TV on the other hand always show exactly the same number of frames per second and do not vary one bit. Therefore the variability in frame-rate in games also works to exaggerate the impact of lower frame-rates, making them more noticeable. In Crysis for example, if you walk out of an indoor area which has 60 FPS into a outdoor area with 25 FPS, you will notice the difference, partly due to a change in control responsiveness, and partly because your eyes detect the relative change in frame-rate.
Testing has shown that human beings can regularly distinguish differences of one frame in 200 every second. There is no actual theoretical limit on how many frames the eye can distinguish. In the natural world, human eyes don't digest motion in terms of a series of still frames, they take in a constant stream of analog movement data. In particular, we are quick to notice dramatic contrasts, no matter how brief. If there is a gap or brief fluctuation in the flow of visual data, then our eyes and consequently our brain can actually pick this up if it's relevant, even if it's subconscious - it all depends on the context of the data streaming in.
So to come back to the question of how many FPS is enough, in my experience, and for most practical purposes, a frame-rate of around 60 FPS is completely sufficient as a maximum FPS. Even 25 or 30FPS can be totally sufficient in slow or medium-paced games - particularly if the game has motion blur, softer edges, and does not display significant variability or stuttering. If there's one thing that would be perfect to have in any game, it would be a method of maintaining a fixed frame-rate. Unfortunately this is not practically possible on many systems because of the different types of hardware used. You can enable V Sync to cap the maximum frame-rate and hence reduce FPS variability, but this may also reduce performance.
Or what he said...i was too slow again. LoL
