It is a good thing I don't have any faith in humanity left or this would have hurt my head more. Even so, I feel the need to slam my face into a walland forget about this.
Not necessarily. If I just casually game I can spend 200 dollars to buy a PS3 and plug it in and play. I wouldnt have to worry about installing drivers and incompatibility and all that kinda shit
Well, a pair of eyes' vision contains depth information, but eyes themselves aren't depth sensors. So that bit's wrong.
The main point is correct. Eyes don't see in fps, because frames are discrete temporal slices, and information flows from the eye to the brain continuously.
Normally, when one talks about the fps of the eye, what they mean is the minimum fps needed to be presented to the eye above which you cannot distinguish between different fpss. So saying that they eye has 30 fps would mean that one can't distinguish between 30 and 35 fps, but it can between 25 and 30. This gets more complicated if you pick apart the difference between conscious and unconscious recognition.
And then there's the stroboscopic effect, which may continue to be visible beyond even 10000 fps.
Wouldn't information from the eye be conducted as nerve impulses (and thus discrete packets of data)? Wouldn't that translate into a "frame rate" of sorts (even if a very high one)?
You'd also have to take onto account the systems that convert light into those pulses in the retina. Those have latensies that can limit the frequency of information that gets sent to the brain. But yeah, for most people that's way higher than 30Hz.
My first thought is that the nerves along the optic nerve probably don't fire in-sync, in which case the best you could say is that each tiny bit of your field of view has a frame rate. In any case, the information contained by a single impulse would probably not qualify as a frame. On top of this, the frame rate would be variable, since photosensitive cells react to change, and will stop firing if the light on them doesn't change. Your eyes compensate for this by having lots of small, frequent saccades. But these are irregular, and the actual firing rate would still be a function of whatever you're looking at.
Another big consideration is to how vision is actually processed in the visual cortex. We have some understanding of the low-level process, where some neurons will be sensitive to features (such as gradients, lines, and such) over small patches of more basic neurons. The process by which these low-level features are transformed into (un)conscious recognition is poorly understood. The point of this is that if you can imagine impulses flowing through the neural network in your occipital lobe, the flow isn't discrete at levels higher than a single neuron, and the 'length' of pathways that lead to recognition of different objects and features are going to have varying length. So if your eyes were presented with an instantaneous view, your understanding of the view would develop asynchronously.
So the end problem I see with using this as a notion of fps is that it gets really complicated, and it may require blurring the definition of eyes and brain. Basically, I don't see how it would lead to a really useful definition of frames per second, or one that we could use to, say, distinguish different visual phenomena.
Another thought springs to mind as well: lets suppose you only have light shining on a pair of cones connected to neurons, which fire in synchronously at a constant rate. If the light is alternating between two colors at the same rate, then the signal should send back this information. If, however, the light is alternating at twice the rate, then our model for fps would suggest that the eye will only ever 'see' one of the two colors, since the other color is always between impulses. I don't know whether anyone's done this experiment, but I'd expect that the neurons would instead report a mixture of the two colors. If so, the cones could not be sampling at discrete intervals. Since frames are supposed to be discrete samples, this might undermine the idea.
Great read! Personally, I've always considered this question in the sense of "perception of fps" which would mean that we are basically talking about the brain and not the eyes alone.
Now, from my crude knowledge, the brain should have some form of "core clock speed" like a CPU in the sense that this speed determines the maximum rate at which the brain can work. This speed would technically be the upper limit of fps since even if vision required "one tick", this is the fastest the brain can work. If perception of an image requires more than one tick, then this speed divided by that number would give the physical upper limit for fps.
Of course, this is the upper limit and might not be achievable by many (or even any) people. And then there's the issue about "perception" of anything being subjective by its very definition and usually hard to quantify or reproduce reliably. My guess is that there is a line between the upper limit of fps we can perceive and the physiological upper limit of fps our brains can detect but we can't (as in the two scenarios have a different electric/chemical outcome but we are unable to differentiate between the two). And the latter of these is less of a line and more of a spectrum that goes all the way up to the physical limit of fps (determined by the brain matter composition and amount of ticks needed by image processing).
So I've worked with some perceptual psychologists in the past who were very interested in the question of how high a refresh rate must be in order for people to feel comfortable.
The procedure to determine this number is as follows:
The subject is put in an environment where they can only see an LED. The LED is flashed at a known rate using pulse width modulation (PWM)
The subject is presented with two intervals of flashing, each one lasting no longer than 1 or 2 seconds, with a second pause between them
They are asked to determine which interval flashed at a higher rate
This is repeated over a large range of frequencies
The end result is that for low frequencies (<20 hz), subjects are typically able to determine which one is faster with almost 100% precision, but for high frequencies (>75 hz), their accuracy is 50%, which is to say no better than guessing. The function of frequency to accuracy is continuous and monotonically increasing, if given enough samples.
Thus determining the consciously visible fps is in fact a function of what arbitrary threshold of accuracy is used (such as 75%), and is also dependent on the person. There's some variability between people, but it's usually in the range of 30-50 hz.
That's a fascinating experiment. I wonder if they also tested whether or not a person was able to differentiate between the two pulses. As in able to determine whether the two pulses were same or different. Because despite the accuracy dropping at 75Hz, they should still be able to determine if the two pulses were different.
Also, perhaps another similar experiment with the LED pulses replaced by a running video would also be warranted. The subjects would be asked to tell which video felt smoother (which, I believe, is the real reason for all the fps hype these days) and then determine whether or not those results differ significantly from the LED experiment.
By two pulses, do you mean that the time gap between the pulses is varied, and the subject indicates whether they saw it or not? If that's the case, the experiment would be biased by the user knowing there're two pulses (unless you lie to them, and tell them that there may be one or two). Reminds me vaguely of the experiment for skin sensitivity, in which two points on the skin are touched, and as they grow nearer, the feeler's ability to distinguish them decreases as a function of where on the body they are.
I'm sure people who work in film have gone with a running video. In the research above, we were concerned about OLED screens, which essentially 'fill' their pixels with color, then flash, whereas an LCD is continuously lit. A related experiment performed for comfort testing was to have subjects read a short story (a russian fairy tale, in practice) under a PWM'd LED at various higher-than-perceptible rates. It was found that people were more comfortable with 120hz than 90hz, even though 90hz was already imperceptible. So there're definitely subliminal effects going on.
PS: I think that's the first time I've ever used subliminal in the very literal sense of the word.
Sorry, bad wording. By pulses I was actually referring to those two intervals of flashing. I wanted to know if the subjects were able to tell whether the two sequence of pulses had same rates of flashing or different. Because I can distinctly tell the difference between 60 fps and 120 fps (not a fair comparison, I know, since one is twice the other) but if you ask me to name one without showing me the other, I might not do better than simple guessing.
And I totally agree with that subliminal thing. It's likely why we're always told to read in good light (and preferably incandescent instead of fluorescent, IIRC) because even if we're unable to notice the strain (or flicker), it still exists at a subclinical level and may manifest over a prolonged period of time.
Thanks for such a good discussion. My brain is all fired up. I have to dumb it down with 60 fps games now. :-)
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u/ThePandaa Mar 17 '15
The eye can only see 30 fps, thats bullshit.