mmm@weitek.UUCP (Mark Thorson) (12/10/85)
Here's an interesting phenomenon. Run your finger along the line of dots from left to right. Do it slowly, so that it takes about two seconds for your finger to cross the screen. Track your fingertip with your eyes. You should be able to see a "race lights" effect, where you see the dots moving. ............................................................................. After a few times, you will be able to track the moving dots without the aid of your finger. The interesting part is the difficulty in making the dots go from right to left. I can see the dots move that direction when I use my finger, but not otherwise. I suppose this is due to developing left-to-right eye muscle coordination for reading. Mark Thorson (...!cae780!weitek!mmm) PS No flames from folks on printing terminals, please.
clarke@utcsri.UUCP (Jim Clarke) (12/13/85)
In article <341@weitek.UUCP> mmm@weitek.UUCP (Mark Thorson) writes: > >............................................................................. > >After a few times, you will be able to track the moving dots without the aid >of your finger. The interesting part is the difficulty in making the dots >go from right to left. I can see the dots move that direction when I use my >finger, but not otherwise. I suppose this is due to developing left-to-right >eye muscle coordination for reading. I find that I can get the dots in phase without finger aid equally easily R to L and L to R. This may be because I have misspent many hours rotating my eyes in order to see whether distant lights are flourescent or incandescent (incandescent ones don't visibly turn off each cycle) and to find out which way TV sets scan. The fact that I have no such difficulty suggests that Mark's explanation may well be correct, I think. (More recently, this trick has turned out to be useful for amusing children, so it's not totally wasted. However, it disgusts most adults. I wish I could see it.) -- Jim Clarke -- Dept. of Computer Science, Univ. of Toronto, Canada M5S 1A4 (416) 978-4058 {allegra,cornell,decvax,ihnp4,linus,utzoo}!utcsri!clarke
jmm@ski.UUCP (Joel M. Miller) (12/13/85)
In article <> mmm@weitek.UUCP (Mark Thorson) writes: >Here's an interesting phenomenon. Run your finger along the line of dots >from left to right. Do it slowly, so that it takes about two seconds for your >finger to cross the screen. Track your fingertip with your eyes. You should >be able to see a "race lights" effect, where you see the dots moving. > >............................................................................. > >After a few times, you will be able to track the moving dots without the aid >of your finger. The interesting part is the difficulty in making the dots >go from right to left. I can see the dots move that direction when I use my >finger, but not otherwise. I suppose this is due to developing left-to-right >eye muscle coordination for reading. > >Mark Thorson (...!cae780!weitek!mmm) > A fascinating visual phenomenon! Its explanation, I think, involves the nature of "smooth pursuit" eye movements and flickering VDT displays. When you look around a stationary scene, you eye moves in little flicks, called "saccades". Most people cannot move their eyes smoothly ("smooth pursuit") unless there is a smoothly-moving target to track. This moving target can be either an actually moving target or a stationary target that is only "apparently" moving. There are many kinds of "apparent motion" but, for now it is sufficient to know that if something seems to move, it can be a stimulus for smooth pursuit. The moving finger provides a target that enables the eyes to move smoothly. The speed of movement at which this phenomenon occurs passes each point in about 0.025 sec, which (I think) is about the interval between screen refreshes. Thus, as your gaze moves, each point flashes on in the same retinal position (the retina is the light-sensitive surface lining the inside of the eye) as did the previous point, so that the retinal situation is unchanging. However, your brain knows your eye is moving (it made it move) and figures that the only way an object's image could remain stationary on a moving retina is for the object to be moving along with the eye. That's what you see. Unless you are one of those people that can execute smooth pursuit eye movements in the absence of a moving target (I'm not), you'll have to get each half-cycle going with your finger, but then the finger can be removed, and the apparent movement of the dots will drive smooth pursuit and sustain the phenomenon to the end of the line. I don't find any any directional assymetry, myself. -- Joel M Miller; Smith-Kettlewell Institute of Visual Sciences 2232 Webster St; San Francisco CA 94115; 415/561-1703 {ihnp4,qantel,dual}!ptsfa!ski!jmm
levy@ttrdc.UUCP (Daniel R. Levy) (12/15/85)
In article <341@weitek.UUCP>, mmm@weitek.UUCP (Mark Thorson) writes: >Here's an interesting phenomenon. Run your finger along the line of dots >from left to right. Do it slowly, so that it takes about two seconds for your >finger to cross the screen. Track your fingertip with your eyes. You should >be able to see a "race lights" effect, where you see the dots moving. >............................................................................. >After a few times, you will be able to track the moving dots without the aid >of your finger. The interesting part is the difficulty in making the dots >go from right to left. I can see the dots move that direction when I use my >finger, but not otherwise. I suppose this is due to developing left-to-right >eye muscle coordination for reading. >Mark Thorson (...!cae780!weitek!mmm) >PS No flames from folks on printing terminals, please. Gee whiz, I can't even notice it at all. The dots blur a bit while following with my eyes, but don't move at all. Could color of terminal screen have an effect? (I am using a light amber screen; I can't stand staring at green screens.) -- ------------------------------- Disclaimer: The views contained herein are | dan levy | yvel nad | my own and are not at all those of my em- | an engihacker @ | ployer or the administrator of any computer | at&t computer systems division | upon which I may hack. | skokie, illinois | -------------------------------- Path: ..!ihnp4!ttrdc!levy
wmartin@brl-tgr.ARPA (Will Martin ) (12/17/85)
In article <642@ttrdc.UUCP> levy@ttrdc.UUCP (Daniel R. Levy) writes: >>Here's an interesting phenomenon. Run your finger along the line of dots >>............................................................................. > >Gee whiz, I can't even notice it at all. The dots blur a bit while following >with my eyes, but don't move at all. Could color of terminal screen have >an effect? (I am using a light amber screen; I can't stand staring at green >screens.) Glad to hear it! I thought I was alone!!! I, too, have gotten NO effect at all from this experiment. I use an ADM42 (white letters on black screen) terminal. I haven't tried looking at this on a VT100 or other type of terminal, though. To those who see the effect -- have you had a chance to try it with a wide variety of display types? Does it show up only on some and not on others? Maybe it relates to quality of display. I spend all day staring at my terminal, so I have chosen this ADM42 which has better-formed letters and a clearer display than any other type around here (except maybe some of the amber types). Will Martin UUCP/USENET: seismo!brl-bmd!wmartin or ARPA/MILNET: wmartin@almsa-1.ARPA
ccrdave@ucdavis.UUCP (Lord Kahless @ Imperial Propoganda) (12/18/85)
At Davis, we use a lot of Microterm Ergo 320's. They're cheap copies of a 220. When they took away our 220 and gave us a green screen 320, my eyes thought they were going to die. Three hours working on that cheap monitor under fluorescent lights, and I always had a severe headache and often had difficulty seeing well enough to read a printed page. After much begging, I managed to get an amber screen 320. The monitor resolution is still terrible, but I don't get the same incapacitating headache and eye strain. Anybody else notice that a lot of the cheap green monitors just KILL your eyes when you're working under fluorescent lights? Also, what's the best vt100 type terminal for someone with very bad eyes?
wcs@ho95e.UUCP (Bill.Stewart.4K435.x0705) (12/19/85)
In article <488@ucdavis.UUCP> ccrdave@ucdavis.UUCP (Lord Kahless @ Imperial Propoganda) writes: >Also, what's the best vt100 type terminal for someone with very bad eyes? Human Designed Systems (the people who did the Concept 100 series) put out a very nice VT220 emulator, with a 15" screen, good phosphor, and lots of added keys, including ESC and function keys. I don't have a reference to it here, but they're in Hockessin, Delaware. -- # Bill Stewart, AT&T Bell Labs 2G-202, Holmdel NJ 1-201-949-0705 ihnp4!ho95c!wcs
hes@ecsvax.UUCP (Henry Schaffer) (12/19/85)
The new inmac catalog (47th edit. Dec./Jan. '86) has a notice on the cover: "Breakthrough! New protection from possible side effects of CRT radiation." The page in the catalog that deals with their product (Anto-Radiation Glare Shield $169/qty 1) points out that there is controversy on whether "CRT radiation" casues health problems. Note that they use the term "radiation" to include "Ionizing Radiation" and their screen "block X-rays & soft X-rays" and also "Non-Ionizing Radiation" "At the base of the spectrum it [the screen] blocks very low-& extremely low-energy waves." Is it legitimate advertising to say, "Is low radiation dangerous? No one know but our shield blocks it, as well as X-rays & electromagnetic interference that can distort data." They say they have a free booklet presenting both sides of the CRT radiation controversy. Write: The CRT RAdiation Debate, Inmac, 2800 Campus Drive, Suite 150, San Mateo, CA. 94403 --henry schaffer -standard disclaimer- p.s. my crt is emitting radiation in the visible light frequency band, and my life would probably be much improved if this could be removed.
levy@ttrdc.UUCP (Daniel R. Levy) (12/20/85)
In article <488@ucdavis.UUCP>, ccrdave@ucdavis.UUCP (Lord Kahless @ Imperial Propoganda) writes: > >Anybody else notice that a lot of the cheap green monitors just KILL your >eyes when you're working under fluorescent lights? > >Also, what's the best vt100 type terminal for someone with very bad eyes? Even good green monitors bother some people. Personally I like white the best followed by amber, but some people can't stand staring at white, either. Let me put in a plug here for the AT&T 5420 and 5425 terminals. They come in both green and amber (sorry, no red ones yet :-). The resolution is quite good. They support a superset of vt100 functions. -- ------------------------------- Disclaimer: The views contained herein are | dan levy | yvel nad | my own and are not at all those of my em- | an engihacker @ | ployer or the administrator of any computer | at&t computer systems division | upon which I may hack. | skokie, illinois | -------------------------------- Path: ..!ihnp4!ttrdc!levy
steve@jplgodo.UUCP (Steve Schlaifer x3171 156/224) (12/24/85)
> In article <488@ucdavis.UUCP>, ccrdave@ucdavis.UUCP (Lord Kahless @ Imperial Propoganda) writes: > > > >Anybody else notice that a lot of the cheap green monitors just KILL your > >eyes when you're working under fluorescent lights? > > > >Also, what's the best vt100 type terminal for someone with very bad eyes? > > Even good green monitors bother some people. Personally I like white the > best followed by amber, but some people can't stand staring at white, either. > > Let me put in a plug here for the AT&T 5420 and 5425 terminals. They come in > both green and amber (sorry, no red ones yet :-). The resolution is quite > good. They support a superset of vt100 functions. > -- I would also plug the Tektronix 4105, 4107, 4109 series of color graphics terminals. They support ANSI (VT100), and VT52 functions and you can select both the color of the character, the color of the background around the characters and the color of the screen area where no characters have been placed yet. I like to use white characters on a blue background with the cleared screen area also blue but others in my area use differant combinations. The point is, you get to choose what you find pleasant (although at a price, the terminals aren't cheap). Steve Schlaifer (jplgodo!steve)
ccrdave@ucdavis.UUCP (Lord Kahless @ Imperial Propoganda) (12/26/85)
> > In article <488@ucdavis.UUCP>, ccrdave@ucdavis.UUCP (Lord Kahless @ Imperial Propoganda) writes: > > > > > >Anybody else notice that a lot of the cheap green monitors just KILL your > > >eyes when you're working under fluorescent lights? > > > > > >Also, what's the best vt100 type terminal for someone with very bad eyes? > > > > Even good green monitors bother some people. Personally I like white the > > best followed by amber, but some people can't stand staring at white, either. > I would also plug the Tektronix 4105, 4107, 4109 series of color graphics > terminals. They support ANSI (VT100), and VT52 functions and you can select > both the color of the character, the color of the background around the > characters and the color of the screen area where no characters have been > placed yet. I like to use white characters on a blue background with the > cleared screen area also blue but others in my area use differant combinations. The 4105's we have here at Davis aren't bad, but the convergence tends to be terribly fuzzy. Tek doesn't seem to be able to fix it. The 4107 is better, but a 220 with amber monitor seems MUCH easier on my weak eyes.
henry@utzoo.UUCP (Henry Spencer) (01/03/86)
Speaking of Tektronix displays and color, the most amusing Tektronix
emulation I ever saw was at NYIT, on their color frame buffers. Faithful
emulation of the Tek 4014 -- including the use of light green print on a
dark green background! Don't remember if it flashed the screen when you
cleared it, though...
--
Henry Spencer @ U of Toronto Zoology
{allegra,ihnp4,linus,decvax}!utzoo!henrymmm@weitek.UUCP (Mark Thorson) (01/06/86)
In article <6259@utzoo.UUCP>, henry@utzoo.UUCP (Henry Spencer) writes: > Faithful emulation of the Tek 4014 -- including the use of light green print > on a dark green background! Don't remember if it flashed the screen when you > cleared it, though... If it were REALLY faithful, you'd see a faint image from the previous terminal session burnt into the phosphor :-) I can just imagine the day the first Tek scope was made to work: "Hey Joe, come over and look at this thing. Ain't that neat!! Brightness? Oh, the production tubes will be brighter. And they won't have all that crud in the background." Mark Thorson (...!cae780!weitek!mmm) ps I actually liked using those old Tek scopes. A display tube hasn't reached its prime until there's drifts of glowing green snow around the edges :-) It's kinda organic that way.
gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>) (01/06/86)
> Speaking of Tektronix displays and color, the most amusing Tektronix > emulation I ever saw was at NYIT, on their color frame buffers. Faithful > emulation of the Tek 4014 -- including the use of light green print on a > dark green background! Don't remember if it flashed the screen when you > cleared it, though... The "tek4014" program for the DMD does; it also "double-flashes" vectors so they look like they're being drawn on an actual 4014. All this nonsense can be optionally disabled.. ----- By the way, the fellow who got headaches in the room full of burning-in monitor assemblies was probably being affected by the near-ultrasonic sound generated by the horizontal circuits (often transformer laminations vibrating). Even if he didn't consciously hear them, such whistles would lead to irritability and headaches.
ron@brl-sem.ARPA (Ron Natalie <ron>) (01/07/86)
I made the Tektronix salesman sick when I programmed the "ERASE" key on a 4027 to turn the screen bright green and then to dark green when it was clearing the screen. -Ron