trejo@nprdc.arpa (Leonard J. Trejo) (09/16/88)
In article <8501@smoke.ARPA> geoffs@brl.arpa (Geoffrey Sauerborn (TANK) <geoffs>) writes: > > RED is safer than BLUE for stops since it can be seen more >easily. (But White is even better than RED for that reason - but that is >why it is used for headlights). This is rubbish. What is seen most easily depends on many visual factors other than wavelength. Size, retinal eccentricity, background, adaptation level, and temporal properties are a few of these. Other factors being equal, the most detectable wavelengths are yellow green under light-adapted conditions and bluish green under dark adapted conditions. White is better for headlights not because it is seen more easily but because it renders the color of objects that it is reflected from better than any narrow band of wavelengths. > > Physics will tell you that blue (a higher energy frequency) will >travel further than red. This also sounds wrong. I don't think the energy of a photon has anything at all to do with how far it travels. >But a fact of human engineering is that red is >more easily noticed by the eye - especially when other light (sun light) >is interfering. This is why many police vehicle use BOTH red and blue. >Red for Day, Blue for Night. > > Next time you see a police flashing its lights in the extream >distance, you'll see likely notice just the red at first. There may indeed be something special about red as opposed to blue. The blue-sensitive cones contribute almost exclusively to chromatic channels, which are more sluggish than the achromatic channels fed primarily by red- and green-sensitive cones. There is also some evidence that red may be detected sooner than other colors. Thus may have to do with the biological significance or red, as in the sight of blood. Reaction time experiments and visual evoked potential recordings support this notion, but the results of different laboratories have not always agreed. Uttal, for example, found faster reactions to blue, then green, then red (I think he was wrong). Nevertheless, the subject is still controversial. ============================================================================ ARPANET : trejo@nprdc.arpa UUCP: ucsd!nprdc!trejo Phone: (619) 553-7981 Postal Address: Leonard J. Trejo, Ph. D. (AV) 553-7981 NPRDC Code 52 San Diego, CA 92152-6800
mh@wlbr.EATON.COM (Mike Hoegeman) (09/17/88)
In article <890@arctic.nprdc.arpa> trejo@nprdc.arpa (Leonard J. Trejo) writes: >In article <8501@smoke.ARPA> geoffs@brl.arpa (Geoffrey Sauerborn (TANK) <geoffs>) writes: >> RED is safer than BLUE for stops since it can be seen more >>easily. (But White is even better than RED for that reason - but that is >>why it is used for headlights). >This is rubbish. What is seen most easily depends on many visual >factors other than wavelength. Size, retinal eccentricity, >background, adaptation level, and temporal properties are a few of >these. ...more optometrists-on-their-lunch-hour-type talk here.... OH COME ON!! Geoffrey was just trying to make the point that things like scroll bars are such a basic tool that there is probably some merit in defining a standard way of operating one. The stoplight analogy was just poking fun at the original poster's high and mighty vehemence at someone having the gall to try and make a set of guidelines for such a thing. Nothing more nothing less.
trejo@nprdc.arpa (Leonard J. Trejo) (09/19/88)
In article <23293@wlbr.EATON.COM> mh@wlbr.eaton.com.UUCP (Mike Hoegeman) writes: >In article <890@arctic.nprdc.arpa> trejo@nprdc.arpa (Leonard J. Trejo) writes: > >In article <8501@smoke.ARPA> geoffs@brl.arpa (Geoffrey Sauerborn (TANK) <geoffs>) writes: > >> RED is safer than BLUE for stops since it can be seen more > >>easily. (But White is even better than RED for that reason - but that is > >>why it is used for headlights). > > > >This is rubbish. What is seen most easily depends on many visual > >factors other than wavelength. Size, retinal eccentricity, > >background, adaptation level, and temporal properties are a few of...etc. > >...more optometrists-on-their-lunch-hour-type talk here.... ^^^^^^^^^^^^ If I were an optometrist I'd have signed my posting as O.D., not Ph.D. I'm a research psychologist. > > >OH COME ON!! Geoffrey was just trying to make the point that things >like scroll bars are such a basic tool that there is probably some >merit in defining a standard way of operating one. The stoplight >analogy was just poking fun at the original poster's high and mighty >vehemence at someone having the gall to try and make a set of >guidelines for such a thing. Nothing more nothing less. My reading of Geoffrey's message picked up the sarcasm intended for the 'OPEN LOOK' poster. However, mixed in with the sarcasm were some authoritative sounding statements about, for example, which colors are seen better. Having observed how easily wrong information is picked up and passed around, especially about color vision, I felt it necessary to respond. In doing so, I came across very officiously myself, and it seems I goofed about blue light not traveling farther than red in our atmosphere. For these errors, I apologize. L. J. T. ============================================================================ ARPANET : trejo@nprdc.arpa UUCP: ucsd!nprdc!trejo Phone: (619) 553-7981 Postal Address: Leonard J. Trejo, Ph. D. (AV) 553-7981 NPRDC Code 52 San Diego, CA 92152-6800