Science proves gaming is better on CRTs than LCDs

Movies and TVs
First, let’s look at an anomaly. The astute among you might be saying “Okay, that all makes sense. But why then do movies which run at 24fps and TV which can run up to 30fps look seamless rather than jittery like a game would be at these rates?”

Good question, and it’s answered in two forms: display mechanism, and the persistence of vision.

Movies, for example, have been traditionally recorded at 24fps (and we won’t go into why here). When displayed by the projector, to stop you seeing the film rolling the shutter interrupts the light between frames, but as we’ve established these black moments would be quite visible at 24fps. So what’s the solution? Each frame is repeated three times, and the light interrupted three times. This creates a persistence of each frame at an equivalent 72fps, which just happens to be close to the flicker fusion threshold for the majority of the population, which is 75fps.

But why is our brain fooled into seeing a seamless image? The answer is persistence of vision. Going back to the example of shining a torch in your eyes, when light is interpreted to your brain by the cones and rods it’s not a binary operation, it’s a chemical reaction. Both are sensitive to light, and the greater the intensity the greater the effect and the longer before they adjust to the next change in intensity. This is why when you turn a light off at night it takes a number of minutes for your eyes to adapt – you don’t get instant night vision. When it comes to watching film, those repeated frames are still transmitting information to your brain even as the light is interrupted by the shutter, and as it happens faster than your eyes can adjust the illusion of a constant image is created.



TV is a little different, but with a similar principle. Depending on the bandwidth, though traditionally 25 or 30Hz (PAL and NTSC respectively) before digital TV, each frame is rendered in two passes using fields (odd and even numbered lines), again relying on persistence of vision to ultimately create an effective frequency of 50 and 60fps. This is why 100Hz TVs in Australia worked so well – by literally repeating frames, much like a cinema, these displays had an effective frequency of 100fps, double the 50fps we have for PAL (for which you can sometimes see flicker) and creating very solid images on screen.

But film and TV is not your CRT or LCD monitor. These devices can produce constant full frame updates in excess of 100Hz (CRTs) and 60Hz (LCDs) – and you notice the difference between frames because, of course, your flicker fusion threshold is at least 75Hz.

The truth about FPS
So back to the great debate; it’s time to lay the smack down: 30fps isn’t enough, that’s clear. Even 60fps isn’t ideal, but it’s a lot better. And yes, all those Counter-Strike freaks denying LCDs and sticking to their CRTs to pump frames at 100fps or more and saying they can see a difference – they’re not lying. In fact, this is still one area where the CRT rules the roost over LCDs.

Since LCDs default to 60Hz, the maximum frames they can attempt to display is 60fps. As the flicker fusion threshold is around 75fps for the majority of the population, this still isn’t as seamless an experience as it could be.

Of course, we’re talking full frames here, which means vsync on. If you turn vsync off, yes, you’ll be able to break past that 60fps, but as you know you get tearing; but it’s not the display doing this. With vsync off your card is still synchronised with the display at 60Hz, only now it’s displaying the contents of its buffer whether the next frame has finished rendering into it or not, so you get a buffer filled with one frame and partly rendered with the next, resulting in tearing. When you use vsync, the buffer is only emptied when the frame is complete, but since it still needs to synchronise with the display, it – like film – can repeat frames while it waits. The display is still 60Hz, even if only 30fps is being managed at the time (the alternative would be to blank the screen, and you’d notice that more).

Conclusion
The final note to say about frames per second is this: your brain is hella smart, and it’s rather good at picking up discrepancies. In addition to aiming for well above 30fps in games for a better experience, it’s just as important to get constant, not fluctuating, frames. It’s better to run at a constant 30fps than hovering at 20-40fps – the brain notices the lack of continuity more than a consistent frame rate. This is another argument to use vsync – it’ll keep your frames much more consistent and provide a smoother display, even if the maximal framerate is less than having vsync disabled. Just remember to enable triple buffering as well.

This is also the reason games are now capping frame rates – like Call of Duty 4 on the PC capped at 60fps, and Halo on the Xbox at 30 fps (and now you know why, with TVs as the popular display device for the Xbox).

So next time someone insists the human eye can’t notice anything higher than 30fps, laugh a little and then point them to this piece.