Talk:Flicker fusion threshold

"The flicker fusion threshold is proportional to the amount of modulation; if brightness is constant, a brief flicker will manifest a much lower threshold frequency than a long flicker. The threshold also varies with brightness (it is higher for a brighter light source) and with location on the retina where the perceived image falls: the rod cells of the human eye have a faster response time than the cone cells, so flicker can be sensed in peripheral vision at higher frequencies than in foveal vision. This is essentially the concept known as the Ferry-Porter law, where it may take some increase in brightness, by powers of ten, to require as many as 60 flashes to achieve fusion, while for rods, it may take as little as four flashes, since in the former case each flash is easily cut off, and in the latter it lasts long enough, even after 1/4 second, to merely prolong it and not intensify it."


 * *slow clap* --Sisterly harmer (talk) 13:57, 29 June 2014 (UTC)

This article needs a serious revision (Rods vs Cones)
Quotations from the "explanation" part (or, better defined given its discrepancies, obscurum per obscurius):

"Rod photoreceptor cells are very sluggish, with time constants in mammals of about 200 ms."

"The maximum fusion frequency for rod-mediated vision reaches a plateau at about 15 Hz."

"Cones reach a plateau [...] of about 60 Hz"

"The rod cells of the human eye have a faster response time than the cone cells, so flicker can be sensed in peripheral vision at higher frequencies than in foveal vision."

My consequent considerations and arisen questions:

How can rods be simultaneously "sluggish" and "have a faster response time than the cone cells"?

If rods are "sluggish" and they need "time constants" of 200 ms (hence, they would need only 5 stimuli per second instead of 15 to give a stable image since: 1000 ms / 200 ms = 5), why is the flicker threshold of the rods said to be higher than the one of the cones? Isn't 15 Hz < 60 Hz?

Advices (and corrections):

Since this article should be "centred on human observers", specify data about humans, and not mammals, to avoid more chaos:


 * Rods temporal resolution (minimum stimulus period of time the receptor can distinguish): 100 ms


 * Cones temporal resolution: from 10 to 15 ms (therefore their actual flicker threshold should be in the 100 to 66 Hz range, and not a mere 60 Hz, which is why CRT screens, that have a response time of 4 nanoseconds, flicker at a refresh rate of 60 Hz).

Notes:

"To detect a flash of light one after the other, an appropriate integration time is required."

References: "Temporal Resolution", Webvision

Gian92 (talk) 22:34, 5 January 2013 (UTC)

Request for more info.
There is just a small blurb about autistics being able to see the flicker at aparently a much higher rate. Does anyone have any more information on that? The thing that brought me to this article was the other day my son (who is autistic) and I were walking next to a wooden fence with the sun on the other side. Thus as we walked the sun "flickered." My son said, "look mommy I'm watching TV." I asked him if TV flickered like that and he said "yes." I asked "all the time?" and he said "yes." I'm curious to understand the ways in which he percieves his world so if anyone has any more information on this I'd be interested. I'll continue my search and if I find anything I'll bring it back here.

request for clarification
in the article it says
 * "In actual practice, movies are recorded at 24 frames per second, and TV cameras operate at 25 or 30 frames per second, depending on the TV system used. Even though motion may seem to be continuous at 25 or 30 fps, the brightness may still seem to flicker objectionably. By showing each frame twice in cinema projection (48 Hz), and using interlace in television (50 or 60 Hz), a reasonable margin for error or unusual viewing conditions is achieved in minimising subjective flicker effects."

Questions: thank you. -- Procrastinating@ talk2me 14:33, 30 May 2006 (UTC)
 * if the human threshold is preceived as 16, who would someone use a 24 frame rate?
 * what is the difference between chemical film and digital imagery to make it leap from 24-->30 ?
 * if you show each of the 24 fps twice (each frame for the same duration as noraml 24 fps) then you are actually showing the film more slowly, being half the speed! (each frames being static on the creen for tweice the time) this makes no sense.

Answers: In response to your last question, you must understand the concept of a shutter. A cinema film projector shutter operates at 48 Hz, meaning an image flashes on screen 48 times in a second. Since there are 24 frames a second being projected from the film, each frame is flashed onto the screen twice in a row, giving the illusion that there are 48 different frames being projected, even if half the frames are the same. It's just to trick the mind. 24 frames being shown per second is actually very jerky. 48 is more asthetically pleasing.


 * In fact 24fps is not at all jerky (it exceeds the motion fusion frequency) but the flicker is unacceptable. Showing each frame twice reduces the flicker, but adds motion artefacts.  This is because a moving object will appear in the same place twice, then move, and then appear in another place twice.  See http://downloads.bbc.co.uk/rd/pubs/whp/whp-pdf-files/WHP053.pdf section 2.1.1 RichardRussell (talk) 22:11, 23 August 2012 (UTC)

In response to your second to last question, 30 fps versus 24 fps dates back to the 1930's when the NTSC standard was set by the National Association of Broadcasters. It has to do with the analog bandwidth allowed by the technology of that time. Digital has nothing to do with it.


 * To expand on this point, NTSC's 30 fps rate (actually 29.97 fps) was based on the 60 hz alternating current of North American electricity systems. The AC provides a built in oscillation that set the field rate for NTSC (60 half frame fields per second = 30 full frames per second). Europe, which had a 50 hz AC system, chose 25 fps television for a similar reason.--NWoolridge 13:48, 6 June 2006 (UTC)

To the first question: why would one want to make a film at 16 fps? While a human may be able to perceive it as fluid motion, it may be very uncomfortable to watch. Filmmakers wanted it low so they could use more film stock and not run out as fast (today, a Panavision film stock lasts only 3 minutes, even at 24--imagine how little it would last at 30 or higher!) But they discovered that as you approach numbers below 24, it became uncomfortable to watch. 24 became the standard.


 * There are two concepts being conflated in the article and we should probably try to disentangle them. One concept is how often a light has to flash before humans no longer can perceive any flickering of the light. That number varies a lot depending upon at least the following factors:
 * The particular subject you're testing (you and I probably vary in our sensitivity to flicker)
 * How fatigued the subject is (flicker sensitivity goes up as you get more tired)
 * No, it goes down.
 * How bright the light source is (flicker is seen more easily with brighter sources)
 * Whether the subject is viewing the flicker with their central or peripheral vision (peripheral vision is much more sensitive to flicker)
 * Whether the object is stationary or moving past your vision field; since the stroboscopic effect can be detected at much higher frequencies than flicker fusion threshold. —Preceding unsigned comment added by Mdrejhon (talk • contribs) 18:29, 22 April 2008 (UTC)


 * Concerning the relationship between flicker and fatigue. I read an abstract of a study (I don't have subscriptions to journals) that said exposure to fluorescent tubes tended resulted in a speeding up of brain waves. The result of this was fatigue and a increase in errors and decreased awareness. There is a an article on Brainwave synchronization in Wikipedia and I suspect this process is taking place. I suspect that there is a subconscious perception, which becomes more conscious due to Brainwave synchronization. I defiantly notice flicker more when tired or after prolonged exposure.

Charleskenyon (talk) 17:55, 4 September 2008 (UTC)


 * Many folks can see flicker up to about 75Hz under typical "viewing the computer monitor" conditions. Monitors tend to be bright, viewed at least partially with your peripheral vision, and used by tired users, so they tend to get the worst of all worlds, leading people to choose refresh (flicker) rates of 75 or even 85 Hz. Television, by comparison, tends to be viewed with your central vision so 60Hz was deemed to be "good enough" and there were other good technical reasons to choose 50Hz in parts of the world with 50Hz power, even though nearly everyone can perceive the 50Hz flicker.


 * The other concept is how many discrete images must be presented each second before we perceive them as representing continuous motion. This number is a lot lower than flickers/second. Most people see 24 frame/second movies as being "continuous" and many cartoons were only drawn at 12 frames/second. TV, at 25 or 30 half-frames per second is seen as fine, and if you've ever seen 50 frames/second movies, you'd say "Wow! That's great!*" And even though a movie is only showing you 24 discrete images per second, the projector shutter is arranged so the light source flashes 2 or 3 times per image, leading to a 48 or 72 Hz flicker rate.


 * So maybe we need to re-edit the article to make this all clear.


 * What does everyone else think?


 * Atlant 15:54, 30 May 2006 (UTC)


 * * This leads to a third confounding factor. Computer gamers tend to talk about "frame rates" as a bragging point of how studly their computer hardware is. It's perceived as "better" if their computer hardware can generate, say, 150 frames/second rather than 37 frames per second and, up to a point, they're correct: as with cartoons, movies, and TV, more discrete images per second leads you to perceive motion as being smoother. But there's a technological limit: once they exceed the refresh (flicker) rate of their monitors, the additional frames they're generating aren't even displayed, so all those "go fasts" just go to waste. If the monitor is running at 85 Hz, there's no point generating more than 85 discrete images per second because it just means portions of the additional images will be thrown away.
 * Even if entire frames are never displayed, there still are reasons why very high framerates are desireable. Most of them could be seen to be based in suboptimal to bad programming, e.g. the various "magic framerates" in id software engines, or the higher responsiveness as higher framerates. Running at a consistent 150fps or even 333fps can give you a competitive edge in some games; it isn't necessarily done for bragging rights.
 * Actually, I agree, 150fps and 333fps provides a competitive advantage. Competition gamer don't notice this because of flicker fusion threshold or that they can tell the fluidity, it just means that the pictures arrive more freshly rendered at their computer monitor's refresh.  An image rendered only 1/333th second ago displaying at the monitor's next refresh, versus an image rendered only 1/150th second ago, gives a competition gamer a few milliseconds advantage for reaction time.  Just like the 100 meter sprint, where milliseconds matter at the starting line.   Even if two competition gamers have exactly the same reaction time and cannot tell faster than 60Hz or 85Hz, the competition gamer with 333fps will beat the gamer who has 150fps, because the image can arrive more freshly-rendered at their computer monitor by a few milliseconds ahead of time. Yes, it results in a lot of wasted images that never arrive on the computer monitor, what it ensures that what does indeed gets displayed on the computer monitor, is the freshest-possible frame that has been rendered (i.e. 3D generated) in the smallest possible fraction of a second prior to being displayed at each refresh on the monitor.  True, this is not the only factor, there are also other complexities such as computer monitor refresh lag, since lots of LCD monitors have built in frame buffering, so many competition gamers still prefer CRT, amongst other reasons. —Preceding unsigned comment added by Mdrejhon (talk • contribs) 18:17, 22 April 2008 (UTC)
 * Is your monitor actually capable of displaying 333fps? I'm more inclined to agree with game engine flaws leading to the competitive edge. Not only can players not see that fast, their display hardware is not capable of refreshing that fast either. If any edge is gained by driving video faster than it can be displayed or seen, then it must not derive from the visual display. It must come from input or physics processing or some other aspect of the game engine. Phlake (talk) 12:44, 21 September 2014 (UTC)

great reply, please revise this article
Thank you Atlant and others for your wonderfull reply and putting things in order! It is SO Much easier to read them annotated by points instaed of the clumzy ambiguated text present now in the article. please do feel free to add your information, nad possibly rewrite those sections. I still do not understand
 * why cartoons use such a low rate,
 * why are we using peripheral vision in computer screens (which we seat clsoer to),
 * why is 48Hz shutter makes a moother image, while outputting a 24 fps film all it does is to have more "darken" images from the closing time periods of the shutter.

I've put a re-write tag on the article,. Procrastinating@ talk2me


 * Answers:


 * Cartoons: Remember, every frame needed to be drawn, so doubling the frame rate (roughly) doubled the labor costs, at least in the days prior to computer animation. 12 frames/second was "good enough" to be an acceptable trade-off between the cost and the visual appearance of the finished product. Nowadays, the cmputers can certainly tween between the hand-drawn animation frames.


 * By sitting closer to the computer screen, portions of the screen fall into your "peripheral vision" rather than your central (foveal) vision. The parts of the screen that fall into your peripheral vision are seen to flicker more than the parts of the screen observed by your central vision. I've always assumed this was because, in your retina, the rod cells (more-common at the periphery of your retina) are more sensitive to flicker than the cone cells (more-common in your central-vision area).


 * 48/72 Hz is actually seen as two/three flashes per frame so it doesn't stimulate your "flicker" response as much. And your brain doesn't really notice that it's the same image two or three times in a row. Meanwhile, modern projectors have enough brightness that they can afford to waste the light that doesn't come through druing those periods when the shutter is closed.


 * Atlant 14:15, 12 June 2006 (UTC)


 * Meanwhile, modern projectors have enough brightness that they can afford to waste the light that doesn't come through druing those periods when the shutter is closed.


 * Why don't they just leave each frame on for a longer percentage of time? — Omegatron 19:13, 12 December 2006 (UTC)


 * Nevermind. It's because we're talking about film.  :-) — Omegatron 19:14, 12 December 2006 (UTC)

Indeed this article should be rewritten, not merely revised. Four more items for that rewrite: 1. Two "laws" are mentioned but they are not defined, explained, cited, or adequately related to the concept of flicker. 2. It is demonstrable that cinematic frame rate choices were determined by empiricism, history, and product/vendor success, not by standardization based on science. That's how 16 fps became the silent film standard. Because of film and optical-system capabilities at the time that optical sound was developed, the sound film frame rate was increased to 24 fps to yield adequate audio bandwidth. It had nothing to do with the images! As of 2010, 24 fps is still the standard cinematic frame rate, even for cost-is-no-object IMAX. 3. For the general reader it would be useful to present what is known empirically and scientifically as to minimum frame rates for film projection and direct viewing (e.g., LCD panels) to avoid flicker. 4. The NTSC standard was developed for color television in the 1950s, not the 1930s. North American black-and-white TV used an interlaced field rate of 60 fps and a complete frame rate of 30 fps because of the need for a stable, accurate vertical-sweep time base, for which the power line frequency was available. The slightly lower NTSC frame rate was chosen for signal spectrum reasons, so that the frequency components of its chrominance (color) signals would fit neatly between the frequency components of the luminance (monochrome) signals. That also ensured NTSC signal compatibility with millions of existing black-and-white TV sets. This is documented in the NTSC standard and may already be explained in an article about television. —Preceding unsigned comment added by 216.40.140.5 (talk) 07:10, 5 May 2010 (UTC)

CRT vs. LCD
Article states:

"LCD flat panels do not seem to flicker at all as the backlight of the screen operates at a very high frequency of nearly 200 Hz, and each pixel is changed on a scan rather than briefly turning on and then off as in CRT displays."

This is completely backwards. CRT monitors refresh in a scan, while LCD monitor's images change by turning each pixel on and off rapidly, changing the color and brightness accordingly. Draknfyre 01:11, 16 July 2007 (UTC)


 * Actually, it works a little differently than either explanation. The backlight and the LCD are completely seperate systems in an LCD display, and not all LCDs exhibit flicker at all (some are backlit by non-flickering continuous light sources such as incandescent bulbs or LEDs, and some have no backlights at all, being lit by ambient light). The article is mostly correct insofar as MOST LCDs are backlit by high-frequency fluorescent lamps. As the backlight just makes light, it has absolutely nothing whatsoever to do with the images being displayed and is never adjusted for any reason other than total display brightness.


 * As for the LCD (which is solely responsible for the images you see), what it does to display images is to act as a shutter, adjusting the brightness (I.E.:Luminance, luma) of the light passing through it. LCDs are incapable of adjusting color (I.E.:Chrominance, chroma) at all (this would require them to flicker trillions of times a second!), and it is for this reason that "color" LCDs actually operate by placing a tinted (Red, green, or blue usually, also incapable of altering it's color for obvious reasons) sheet of something transparent in front of or behind each liquid crystal shutter.


 * Aside from color, I don't recall the shutters as adjusting opacity by flickering, but by actually varying their opacity. I could be wrong on that last count.


 * This whole article (and the related articles on framerate and video/film) is riddled with moronic nonsense though, and I'm definitely going to rewrite it whenever I find the time to look up some good material for the poor thing. 207.177.231.9 16:09, 31 July 2007 (UTC)

Physiological Effects
I personally have a high flicker fusion threshold and there is evidence that this has always been so (as a child I would immediatelybecome irritable being taken in to environments only lit by fluorescent tubes, such as supermarkets). More recently I use to go round offices telling people the frequencies CRTs were refreshing I was always correct up-to 85Hz at which point my accuracy dropped. I can see flicker at at 100Hz; fluorescent tubes, sodium lighting and 60W bulbs and often 100W bulbs. Some environments I can't stand (these combined with multiple repetitive sound sources), I have Stemetil (Prochlorperazine Maleate) which seems to help. Having naps also does. The effects are worst in winter as there is little natural light making exposure to artificial sources almost continuous. The flicker causes tiredness so sufferers may believe they suffer from SAD. I have had problems finding information on the topic and would like to know more, any help would be welcome.

Charleskenyon (talk) 13:08, 19 November 2007 (UTC)

For all people, I believe signals of up to something like 150Hz do get down the optic nerve and can be seen superimposed on the brain's EEG readings. It's just that conscious awareness of this varies from person to person. In my case I can't actually see 75Hz CRT as an actual flicker but I can "feel" it, I get the feeling that the display is sort of unstable or ephemeral whereas 85Hz looks rock solid the same as a backlit slide (unless I'm tired when I can sense up to about 100Hz).

What you should do is use compact fluorescents, they typically operate around 30KHz which is imperceptible and the hum is also inaudible being above human hearing. Quite a few people get headaches from 100Hz fluorescents though, and I personally would not use a monitor below 85Hz. I've not met anyone who could perceive the flicker of an incandescent bulb before but they can certainly be used as very weak strobe lighting in certain situations so they do flicker a little, though it's a bright/less-bright thing not an on/off thing. Samatarou (talk) 20:15, 24 November 2007 (UTC)

Thanks I do use compact florescents, they are better than florescents and incandecents with them I can't see the flicker but I can feel it. I have been trying LED and whilst much better than anything else they are still tiring. I suspected that it is because I'm using mains power and the fittings in both cases are not totally recitifing the 50Hz AC - 100hz peak to minium power output, so they switch of during part of the cycle. This seems to be true as I saw a strobe effect with spinning lego. Fully rectified DC supply or a much faster AC standard (very unlikely) is the only solution. Last winter I could see moon shadows whilst walking down a light street, the moon lit and sodium lit worlds interpolated, this I found tiring and weird.

Charleskenyon (talk) 17:25, 6 May 2010 (UTC)


 * Interesting, I can easily see multiple images of anything moving rapidly in the light of LED light fittings,(100Hz flicker). Your moon and sodium experience sounds uncanny; without wishing to seem patronising perhaps accepting that you have an unusual ability rather than a handicap might help with dealing with the situation. Stub Mandrel (talk) 17:35, 12 October 2018 (UTC)

There appears to be a discrepancy between this article and the article on Rod Cells.

Untitled section
Here we have the claim:

“the rod cells of the human eye have a faster response time than the cone cells, so flicker can be sensed in peripheral vision at higher frequencies than in foveal vision.”

But in the rod cell’s article we have:

“Rod cells also respond more slowly to light than cones do, so stimuli they receive are added over about 100 milliseconds. While this makes rods more sensitive to smaller amounts of light, it also means that their ability to sense temporal changes, such as quickly changing images, is less accurate than that of cones.”

I believe the latter is correct. —Preceding unsigned comment added by 87.194.193.70 (talk) 10:22, 13 February 2008 (UTC)

Link
The link to "The Flicker Fusion Factor Why we can't drive safely at high speed" should be removed. The article is inaccurate and does not contribute to this article. 72.87.188.240 (talk) 23:37, 23 February 2008 (UTC)

Stroboscopic Effect versus Flicker Fusion Threshold
I agree that it is important to distinguish the Stroboscopic Effect from the Flicker Fusion Threshold. When an object is in motion, it is much easier to determine that it's non-continuous. The Rainbow Effect of DLP projectors is an excellent example, since 6X colorwheels result in the equivalent of a color sweep of about 360 Hz, yet some people are still able to detect this -- NOT because of flicker fusion threshold, but because of the stroboscopic effect. For example, it is possible to detect 500Hz and even 1000Hz flicker if it is zooming past you - a 1Khz strobe light moving at 1000 inches per second past your field of vision, leaves a dotted trail of flashes 1 inches apart. Photography agrees with this; even when you use a slow shutter that would otherwise not detect this flicker, moving high-speed-flashing objects show up as a dotted line rather than a continuously blurred line. Some scientific references need to be added about this 'indirect' method of determining flicker. Mdrejhon (talk) 18:36, 22 April 2008 (UTC)
 * Since added. --Beland (talk) 14:21, 8 October 2009 (UTC)

Faster threshold: rods or cones?
In the existing Wikipedia article, it says that rods have faster fusion frequencies than cones. Britannica, a long trusted source, on the other hand, argues that the reverse is true, namely, the cones have higher frequencies than the rods (Ferry-Porter law). Which side is true? Thank you, Nuvitauy07 (talk) 01:33, 13 July 2010 (UTC)

Multiple errors in page
This page has many misleading, confusing, and in some cases, simply inaccurate statements. I am not a psychophysicist, so I am reluctant to take on a replacement page, but I am an expert on the molecular mechanisms that control the kinetics of rod and cone light responses. The classic papers on human critical flicker fusion frequency are from Seelig Hecht and co-workers in the 1930's. A definitive one (ref. 6 below) is available at: http://jgp.rupress.org.ezproxyhost.library.tmc.edu/content/19/6/965.full.pdf+html?sid=8c7f3061-91cd-4296-afef-d8fb572bbac2 Figure 3 in this paper shows clearly the the fusion frequency varies systematically with light intensity and wavelength, and that for rods the maximal fusion frequency is about 17 Hz, and for cones it is a little more than 60 Hz (for one subject, who happened to be Seelig Hecht). Other papers document that these numbers vary somewhat from individual to individual, and recent studies document that some genetic deficiencies lead to dramatic decreases in the time resolution of vision known as "bradyopsia."

Refs.:
 * 1. Novel mutations and electrophysiologic findings in RGS9- and R9AP-associated retinal dysfunction (Bradyopsia). Michaelides M, Li Z, Rana NA, Richardson EC, Hykin PG, Moore AT, Holder GE, Webster AR. Ophthalmology. 2010 Jan;117(1):120-127.
 * 2.Six patients with bradyopsia (slow vision): clinical features and course of the disease. Hartong DT, Pott JW, Kooijman AC. Ophthalmology. 2007 Dec;114(12):2323-31.
 * 3. Bradyopsia in an Asian man. Cheng JY, Luu CD, Yong VH, Mathur R, Aung T, Vithana EN. Arch Ophthalmol. 2007 Aug;125(8):1138-40.
 * 4. Defects in RGS9 or its anchor protein R9AP in patients with slow photoreceptor deactivation. Nishiguchi KM, Sandberg MA, Kooijman AC, Martemyanov KA, Pott JW, Hagstrom SA, Arshavsky VY, Berson EL, Dryja TP. Nature. 2004 Jan 1;427(6969):75-8.
 * 5: Hecht S, Smith EL. INTERMITTENT STIMULATION BY LIGHT : VI. AREA AND THE RELATION BETWEEN CRITICAL FREQUENCY AND INTENSITY. J Gen Physiol. 1936 Jul 20;19(6):979-89.
 * 6: Hecht S, Shlaer S. INTERMITTENT STIMULATION BY LIGHT : V. THE RELATION BETWEEN INTENSITY AND CRITICAL FREQUENCY FOR DIFFERENT PARTS OF THE SPECTRUM. J Gen Physiol. 1936 Jul 20;19(6):965-77.
 * 7: Hecht S, Verrijp CD. INTERMITTENT STIMULATION BY LIGHT : IV. A THEORETICAL INTERPRETATION OF THE QUANTITATIVE DATA OF FLICKER. J Gen Physiol. 1933 Nov 20;17(2):269-82.
 * 8: Hecht S, Verrijp CD. INTERMITTENT STIMULATION BY LIGHT : III. THE RELATION BETWEEN INTENSITY AND CRITICAL FUSION FREQUENCY FOR DIFFERENT RETINAL LOCATIONS. J Gen Physiol. 1933 Nov 20;17(2):251-68.
 * 9: Hecht S, Shlaer S, Verrijp CD. INTERMITTENT STIMULATION BY LIGHT : II. THE MEASUREMENT OF CRITICAL FUSION FREQUENCY FOR THE HUMAN EYE. J Gen Physiol. 1933 Nov 20;17(2):237-49.
 * 10: Hecht S, Verrijp CD. The Influence of Intensity, Color and Retinal Location on the Fusion Frequency of Intermittent Illumination. Proc Natl Acad Sci U S A. 1933 May;19(5):522-35.
 * 11: Hecht S, Wolf E. INTERMITTENT STIMULATION BY LIGHT : I. THE VALIDITY OF TALBOT'S LAW FOR MYA. J Gen Physiol. 1932 Mar 20;15(4):369-89.

In any case, it is absolutely wrong to state that rod responses are faster than cone responses, because the opposite is true. — Preceding unsigned comment added by Twensel (talk • contribs) 02:29, 2 February 2011 (UTC)

Display Frame Rate Section is Inaccurate and Misleading
Video broadcast engineer here. Video being 25 or 30 "frames" per second is a misnomer that leads to common confusion. FPS in video is just a technical term related to how many times per second a CRT draws a complete set of lines. It has nothing to do with the actual temporal resolution (number of unique moments in time being displayed in sequence), which is what this article concerns itself with. Broadcast video can display anywhere from 0 to 50 or or 0 to 60 (depending on format) unique moments in time per second, and live television has always been (and continues to be) at the very high end of that range with a temporal resolution of 50 or 60 (59.94 to be precise). Sports, newscasts, multi-camera soaps and sitcoms are all an effective 60 frames per second in the United States & Japan (50 in the UK). The confusion stems from a common belief that two interlaced fields make up one unique image in time and that the only reason frames are split into fields is to reduce flicker (which is the case for film projection, which displays each frame twice). For video this simply isn't true. Anything not from film (or digital video meant to mimic film) that you see on television has an effective frame rate of 50 or 60 because each field (or full frame in progressive formats like 720p) represents a unique moment in time. This has been the case going back to the birth of television. When we see footage of old television programs from the 1950's we see an effective 24 fps because we're watching a film archive. But those who saw the original live broadcast in the US saw an effective 60 fps. So while saying "television is 30 frames per second" is correct in a manual meant for engineers last century, it is inappropriate and misleading terminology for an article dealing with temporal resolution.Lifterus (talk) 18:25, 30 November 2013 (UTC)

An eye phenomenon or a brain phenomenon?
I was taught that the eye received and transmitted information to the brain continuously, but that flicker fusion was the result of the brain only being able to process so much of that information. In other words, while we see continuously, we do not perceive continuously, is that an outdated school of thought perhaps?

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Clarification Needed regarding frequency basis
"it is conventionally, and most easily, studied in terms of sinusoidal modulation of intensity."

Does this means sinusoidal either side of null,as with the flicker of an AC-powered filament lamp, or sinusoidal above a minimum level? In the former flicker happens as TWICE the frequency of the sinusoid and the latter hardly ever occurs in practice. Stub Mandrel (talk) 17:29, 12 October 2018 (UTC)

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Still needs revision
As someone has already pointed out, the contradictory statements about the response times of rods and cones, which have not been corrected, undermine the whole article.Paulhummerman (talk) 13:08, 12 September 2019 (UTC)


 * Moreover, the article just keeps blabbering endlessly in unncesessarily technical terms while mixing up two very different things that should each have its own article: Brightness flicker and framerate.


 * As for framerate: The human eye is very unreliable when it comes to mere change of images by means of framerate, already being fully satisfied with 16fps for the illusion of movement. The only reason we have ever gotten framerates above 16fps for playback were necessities of audio fidelity with sound-on-film systems (thus 24 fps in sound film), and then compatibility problems with mains frequencies in national AC power systems with the advent of television (thus, 50 Hz in Europe and 60 Hz in North America, with further problems with color TV systems eventually leading to 59.94 Hz). That's pretty much all that you need to write in an article about persistence of vision in relation to framerate.


 * But that's not what *THIS* article should be about: (Brightness) Flicker fusion threshold. The temporal sensitivity of the human eye is notably higher when it comes to brightness flicker than it is with mere framerate, maxing out around 48-50 Hz. Yes, it's also affected by overall brightness, but there's a certain overall brightness limit and standard before your eyeballs start melting. Being a rather light-sensitive sufferer of migraine, I know what I'm talking about here when it comes to standard brightness levels in monitors and film projection, and I can live fairly well with them.


 * The claim in the article that the brightness flicker threshold in the article would be as high as 60 Hz is a common, traditional confusion with the electronic mains frequency problems of NTSC (see above). The only reason the human eye sees a difference between 16fps and 60 fps (often confused with 60 Hz, especially when it comes to modern framerate interpolation) has nothing to do with framerate *OR* brightness flicker. The difference the human eye sees there is:


 * a.) Different amount of motion blur in natural 60fps photography (the higher the framerate - or rather, the faster the shutter speed - the lower the motion blur). 3D animators know that motion blur is crucial when it comes to maintain the illusion of fluid motion, and cinematographers know that the standard, ideal shutter speed is 180° aka "half the framerate".
 * b.) Terrible motion artifacts in artificial modern framerate interpolation (where the larger the gap between natural and interpolated framerate, the *MORE* artifacts are being added).


 * Utter ignorance to both a.) and b.) leads to the horribly choppy soap-opera effect with modern digital framerate interpolation (and cheap denoising filters on many modern digital TVs) which uneducated laypeople even perceive as some kind of "improvement".


 * Out of the two sources given for the false claim that the brightness flicker threshold would be 60 Hz, one is not available on the internet, and the other does not only not even mention any such figure, but is even nothing but a mere newsgroup post or private e-mail on "where to see videos played back at different speeds". So not only is the claim not included in the source, but it entirely lacks qualification as a proper source for Wikipedia as per WP:RS. --46.93.146.87 (talk) 14:53, 26 June 2021 (UTC)


 * P. S.: A lot of the talk on this talkpage on the brightness flicker threshold being even higher than the 60 Hz of NTSC is bullshit relating to entirely different gaming monitor issues that are actually due to the rainbow effect found not only in DLP projectors but also certain flatscreen TVs and computer monitors, and to notorious syncing issues between graphics cards and monitor refresh rates (cf. posts above such as "I can see way faster than 100 Hz!"). A video game may officially run at 150fps, but due to syncing issues, the effective framerate is even below 16fps. And when somebody claims above that the silent-film standard of 16fps and the soundfilm standard of 24fps were "not chosen because of science of the human eye", they ignore the difference between framerate and brightness flicker. There's a reason why 16fps and 18fps projectors have a three-blade shutter (16 * 3 = 48 Hz brightness flicker and 18 * 3 = 54 Hz) and 24fps projectors have a two-blade shutter (2 * 24 = 48 Hz). --46.93.146.87 (talk) 16:27, 26 June 2021 (UTC)

Wiki Education assignment: Human Cognition SP23
— Assignment last updated by AbigailG23 (talk) 05:13, 9 April 2023 (UTC)

Error in "Non-human species" section
There appears to be an error in the non-human species section that was missed during the general revisions. It states that dogs (and other mammals) will have a higher fusion threshold due to higher percentage of rods to cones. However, rods have a lower threshold (i.e. fusion occurs at a lower frequency) compared to cones, not higher, so the statement does not logically follow. 129.94.8.13 (talk) 06:32, 31 October 2023 (UTC)