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Framerate : two candid questions (really ... LOL)

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Is there a need to go, everything being equal (sliders), beyond 24 FPS which is is the speed movies are running to spectators satisfaction (no apparent jerkiness) ?Is there a sense of having a fps rate superior to the screen refreshing rate ?Dominique

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I don't know about the 2nd question (frame rate and screen refresh rate), but I've found that if I can maintain anything at or above 18 fps, my simming is smooth and stutter free -- easily smooth enough to control a helicopter. By default the program sets my frame rate at 25, but I've locked it at 20. Works for me! -Lindy :-rotor:-wave

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Hi Dominique,The answer to the first is yes.The reason is quite simple: a projector and a monitor are completely different. Film in a projector with a backlight bulb displays an entire frame at the speed of light every 1/24 of a second. A monitor has electrical/mechanical parts that "draw" a frame one line at a time (or every other line then repeat to fill for interlaced displays). The two are wholly incomparable because their method of arriving at the same result is completely different. Those who make the silly argument that 24 fps is perfect on a TV or monitor because thats what film is shot at are simply making an uniformed assumption.A simple monitor test to prove this for anyone is to make your monitor draw 60 frames per second (set the refresh rate to 60Hz). Do you see a difference than at, say, 85Hz? If 24fps is sufficient then this should be way overkill - but its not. Why? Because a monitor "draws" a frame pixel by pixel, line by line - it doesn't "project" a full frame almost instantaneously.A standard NTSC television is slightly different: because it is interlaced, it draws a half a frame at slightly less than sixty times a second (60Hz). This effectively gives you 29.97 full frames a second. For the software it was designed for (full motion video at 324x243 resolution), this almost always works just fine. Software such as DVD's with 720x480 resolution really starts to push what can look good on an NTSC display (hense most standard TV's today have 480 or greater lines of resolution, but their refresh rate is still the same). New higher end HDTV displays can refresh at a full 60 frames per second (and more) because the content is much more complex and larger: just like computer software.60 frames per second drawn on a monitor refreshing 85 or more times a second is accepted as a "great" display. Any less fps can still be acceptable depending upon the software and its motion, but thats the target. At 85Hz refresh, getting 85 fps is optimal.As for the second part: it depends on motion in the software. If the generated motion is faster than the monitors refresh rate, then yes a higher frames per second than the refresh is desired for things not to be "jumpy" - even if barely perceptible at higher refresh rates. On the opposite end, software such as Flight Sim can happily get away with low fps because its on screen motion is one of the lowest of any genre.Take care,Elrond---Not enough bandwidth to display this signature! Don't reformat hard drive? (Y/N)

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Thanks Elrond, for your answer. Allow me a follow up to ask for further clarification. I'm no hardware guru :)Frame rate and screen refreshment are obviously linked but seem two different things ? Lowering the refresh rate to 60 Hz from say 85 Hz strains the eyes because each dot on the phosphor coating gets dimmer too soon before being lit again creating a fluctuating fuzziness. But it does not affect the illusion of motion (jerkiness). BTW doesn't a LCD screen work in a similar way of the frame shuttering of a movie ? On the other way round if you go from 24 FPS down to 12 FPS, a movie gets silly but no eyestrain.So if 24 hz would be unbearable, 24 fps gives a good illusion of motion as Lindy pointed out.Dominique

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Yes, framerate and screen refresh are two different things. On standard film the two are always in sync due to physics (light projection). On television, the framerate is 30Hz while the refresh is 60Hz, hence its interlaced design - the brain is capable of filling in the half missing information at each 60Hz refresh. On the computer, framerate and refresh vary wildly of course. If you watch a DVD on a computer or HDTV for example (at the exact DVD resolution of 720x480), the monitors higher refresh rate allows the brain to decode a lot more detail than you'd see on a standard NTSC TV. Even when resolution and dpi are identical, the higher refresh rate gives the brain more information to work with.The phosphor rate is an aspect I didn't bring up... You are absolutely right. NTSC was originally designed at 30 fps to achieve less motion artifact than film, but they made televisions interlaced to keep phosphors refreshed: at 60Hz (sixty times a second). This effectively eliminated the phosphor problem.Our brains work hard to interpret and artificially fill in any gaps in information. The human mind is extremely successful at doing just this type of work: one of the reasons we are so good at making connections between seemingly disparate pieces of information. That doesn't mean, however, that more information isn't "detectible". One way that lower framerates in both film and TV help the mind fill in for the missing information is the motion blur in each frame: if you ever pause a DVD you'll see it clearly. Computer generated images lack this important detail (most of the time) and thats another aspect to the motion problem for our brains at low framerates.Besides flip cards and other gimmicks, film of course was the first full motion device. The 24 fps mark was the lowest that could be used before the brain couldn't keep up with filling in for missing information - thus 24 fps was chosen to save money in physical film cost. If you've ever sat at the front of the theatre and watched 24fps film up close, you know how motion artifacts are visible and distracting for your brain at that rate. When television came along, radio bandwidth was available to increase the rate to 30 fps but not much more without restricting the number of channels to an unacceptable level: this gave the brain some help in viewing action with better detail and thus a "smoother" picture. Now that NTSC is being replaces with ATSC HDTV, a lot of that data can be compressed and still fit in the same amount of bandwidth. Hence, while 30Hz is still the lowest of the standard, they've provided the capability to encode content at up to 50Hz and even 60Hz. If your eye and brain couldn't detect this, why would they do it? Because your eye and brain can. Film and television framerate was all about economics, not eye and brain capability.On a different track: there were studies into subliminal suggestion in television advertising in the late fifties (I'd provide the link since it was so interesting, but I can't find it at the moment). Part of the work focused on how much information the brain could resolve for a single frame in a 30Hz stream. The answer was: extreme detail. The brain can decode individual frames well into the high nineties rate depending upon content and contrast. The whole reason subliminal suggestion works at even high frame and refresh rates (60Hz and more) is because the eye and the brain respectively can see and fully resolve a single frame clearly at that rate. The higher the contrast (such as white objects on a black background), the better the detection at the highest of framerates. This just so happens to be where a lot of natural motion resides as well: high contrast parts of a frame.Sorry if this turned out to be a rambling mess! :-lol This is one subject I've always been fascinated with and couldn't help myself. I hope the answer you were looking for was somewhere in there... :-)Take care,Elrond---Not enough bandwidth to display this signature! Don't reformat hard drive? (Y/N)

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For the type of 'flying' we do there is little value in greatly exceeding 24fps. Frame rates up to 70fps are used in specialised movie formats like Showscan and HD IMAX and those are supposed to provide a better sense of speed. I saw a Showscan movie once but I can't say it crossed some magic boundary of immersion that made me feel as if I was actually moving with the scene, which is what the promoters claimed.High frame rates would probably only show a noticable benefit with a jet fighter sim, doing low level high speed attack runs where you see the ground and objects rushing around you.You can ignore that stuff about T.V. and monitor refresh rates needing to be 60 or more. That is only to prevent flicker, even with static scenes, and has nothing to do with the rate of change of a scene, which is what we are taking about with fps.If we had a real 'blur' effect for the 24 fps and lower rates it would probably improve the motion perception. That is what Spielberg and CGI companies add to make dinosaur motion realistic, and why motion in 'Claymation' movies always looks odd, because each frame is too crisp and shows no blur effect. However, at higher frame rates the blur effect is supposedly not required (as is the case in real life).As to the second question, there is no benefit to having a frame rate higher than your monitor's refresh rate, if you have a fps of 120 and a refresh rate of 60, then you are just missing every second frame and your computer is wasting its time generating it.

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