Talk:Flicker fusion threshold

message: "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)
thread_title:  

message: 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"The period of integration is up to 100 ms for rods."
* Cones temporal resolution: from 10 to 15 ms"And up tp 10 to 15 ms for cones." (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)
thread_title:  This article needs a serious revision (Rods vs Cones) 

message: 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)
replies: text: 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)
thread_title:  Physiological Effects

message: 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)
thread_title: Untitled section

message: 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)
thread_title:  Link 

message: 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)
replies: text: Since added. --Beland (talk) 14:21, 8 October 2009 (UTC)
thread_title:  Stroboscopic Effect versus Flicker Fusion Threshold 

message: 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)
thread_title: Faster threshold: rods or cones?

message: 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)
thread_title:  Multiple errors in page 

message: 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)
thread_title:  Display Frame Rate Section is Inaccurate and Misleading 

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message: "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)
thread_title:  Clarification Needed regarding frequency basis 

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thread_title:  External links modified 

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

message: 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)
thread_title:  Error in "Non-human species" section