Results 1 to 16 of 16

Thread: Chromatic aberration & depth perception

  1. #1
    OptiBoard Novice
    Join Date
    Aug 2005
    Location
    Sydney
    Posts
    3

    Chromatic aberration & depth perception

    Hello.

    I recently switched from contact lenses back to glasses and am experiencing some annoying effects. Firstly I see coloured red or blue halos on high contrast boundaries in my peripheral vision. Secondly, 2D printed or projected images involving solid blocks of saturated colors, e.g. red text on a blue backgound, give a strange effect where the different colors appear to be floating on planes lying at different depths. Would I be right in assuming that both of these are a consequence of chromatic aberration? Seeing as the lenses are only -1.75 D I am suprised and wonder how people on 5+D can see anything at al!? Also I never experienced this with my old glasses. The material is polycarbonate -- I was told this would be "thinner" than "plastic" (which I took to mean it has a higher refractive index than the standard polymer used for lenses) so again I am surprised -- does it really have a lower refractive index but more dispersion?? I need safety lenses for shooting but at this rate I might just get a pair of normal plastic ones and save the polycarb for shooting only.

  2. #2
    OptiBoard Novice
    Join Date
    Aug 2005
    Location
    Pa
    Posts
    2

    abbe value

    The problem you are having is from the low abbe value of polycarbonate. The lower the abbe, the more chromatic abberation. I suggest with your relatively low correction you try trivex. Trivex is actually more impact resistant than poly and the abbe is high. The edges will be a bit thicker but with a -1.75 that shouldn't be an issue.

  3. #3
    OptiBoard Apprentice
    Join Date
    Aug 2005
    Location
    UK
    Posts
    23
    You have described an effect that I saw. I thought I was going mad. My CD covers were 3d!

  4. #4
    What's up? drk's Avatar
    Join Date
    Mar 2004
    Location
    Ohio
    Occupation
    Optometrist
    Posts
    7,880
    I too have experienced the "stereovision" effect with a menu of red and blue letters on a black background at my favorite ice-cream shop. I was wearing polycarbonate, and felt that the chromatic abberation must be the cause, a-la red-green anaglyph glasses ("3-D glasses"). To test this theory, though, I returned for another milk shake wearing my RGP contact lenses, and the effect was still there, eliminating chromatic abberation as the culprit, I believe.

    I think some targets just have the effect. I'd have to study up to see what's going on.

    Any visual science posters? I volunteer to do more research.

  5. #5
    OptiBoard Apprentice
    Join Date
    Aug 2005
    Location
    UK
    Posts
    23
    This was definitely a new effect with my polycarbs.

  6. #6
    OptiBoard Novice
    Join Date
    Aug 2005
    Location
    Sydney
    Posts
    3
    thanks for the replies.

    Interesting re 3D effect & contacts ... I'll try the same thing myself. I asked a few non-specs-wearing folk whether they ever experienced the effect and they said no. I was playing around yesterday during a talk when I saw the effect. I found that if I changed the direction of my face, i.e the angle at which rays pass through the lenses, the relative position of different coloured components of the image changed, just like you get with 3d glasses or SIS "magic eye" 3d images...

  7. #7
    Bad address email on file
    Join Date
    Apr 2005
    Location
    Cambridge UK
    Occupation
    Other Eyecare-Related Field
    Posts
    116

    Chromostereopsis

    Chromatic aberration is only part of the effect you are aware of. Chromostereopsis, retinal mapping and sequencing,temporal processing are also likely to be involved.
    Too complex an area for a simple reply, worth investigating alternatives to simple chromatic aberration though.

  8. #8
    OptiBoard Novice
    Join Date
    Aug 2005
    Location
    Sydney
    Posts
    3
    Quote Originally Posted by Ian Jordan
    Chromostereopsis,
    Ah hah, I knew there would be a word for it! Armed with that, I found these pages:

    http://www.ritsumei.ac.jp/~akitaoka/scolor-e.html

    http://ninemoons.com/~daf/chromo.html

    The first example of the first page is particularly striking for me, a very strong and obvious depth effect. When I take my glasses off (doing it at 25 cm away from the screen so it is still in focus w/o glasses) the effect is still present but much more weakly. Also, if I close one eye, the effect is still there but just as weak as with no glasses. The glasses make no difference when viewed through one eye. So my guess is that the non-glasses effect is not a binocular/stereo effect at all but ties in with depth cues present even with one eye shut... whereas the glasses effect is truly a binocular effect, causing a wavelength-dependent change in effective pupil separation and/or object angular size/apparent distance.

    So, I'm still blaming the polycarbonate --- would this assertion be supported by optics theory? I'm sure there must have been a lot written about this stuff already...
    Last edited by russell; 08-23-2005 at 02:13 AM.

  9. #9
    Bad address email on file
    Join Date
    Apr 2005
    Location
    Cambridge UK
    Occupation
    Other Eyecare-Related Field
    Posts
    116

    hope this helps

    Chromatic aberation does not increase by using two eyes. The effects you are describing are at least in part perceptual rather than purely mathematical. The appearance of increased chromatic aberration is probably a mapping effect and may be due to relative retinal sequencing and distribution of fusional areas (using the retinal mathematical sequencing). These effects are often found in conjunction with other sensory effects e.g. hearing filtering difficulties, clumsiness and frontal headaches (and asthenopia).
    In the end it is the lenses that are partly causative but modifying abbe number (dispersion) of lenses may not be the answer.

  10. #10
    OptiBoard Professional OptiBoard Corporate Sponsor
    Join Date
    Jul 2001
    Location
    Los Angeles, CA
    Occupation
    Lens Manufacturer
    Posts
    138
    Then again it might be as simple as changing the lens material. Some people seem to be much more sensitive to low Abbe materials than others. I know lots of people like that.

  11. #11
    Bad address email on file
    Join Date
    Apr 2005
    Location
    Cambridge UK
    Occupation
    Other Eyecare-Related Field
    Posts
    116

    abbe numbers

    A simple question - what do you do when dispersion is not a problem? Do you understand how to determine the difference? Can you determine wheteher it is a dispersion problem without wasting another pair of lenses. It is possible.

  12. #12
    Master OptiBoarder
    Join Date
    May 2000
    Location
    PA
    Occupation
    Dispensing Optician
    Posts
    973
    I agree with CEO. I also would also want to evaluate the OC's in relation to your pupilary distance, base curves & vertex position of the Poly lens as many do not experience the problem unless in higher powers. Generally yellow & blue are the dispersions seen in approximately a 4D poly lens. Some migraine sensitive people I encountered were only able to wear CR-39 because of the higher ABBE value. My suggestion would be the Trivex material first as to its comparable integrity as well as having a higher ABBE that is closer to the human eye before going there.

  13. #13
    Bad address email on file
    Join Date
    Apr 2005
    Location
    Cambridge UK
    Occupation
    Other Eyecare-Related Field
    Posts
    116

    abbe numbers and dispersion

    Whilst dispersion is undoubtedly one of the potential problems there are a number of others, magnocellular processing, retinal sequencing and mapping, temporal processing to name but a few.
    An optician should understand how to tell the difference (and measure it) and not just rely on the hopefully if I change the abbe number it will stop the problem.
    It is necessary to differentiate whether problem persists (or changes) from the primary position to eccentric viewing and to determine whether the effects of centration are critical. Trial end error is not good enough for a professional if there are scientific methods to determine whether problem is dispersion or whether dispersion just appears to be a problem.

    Chromatic dispersion or processing deficits can easily be ruled out/in with instrumentation

  14. #14
    Master OptiBoarder Darryl Meister's Avatar
    Join Date
    May 2000
    Location
    Kansas City, Kansas, United States
    Occupation
    Lens Manufacturer
    Posts
    3,700
    The description sounds like chromatic stereopsis, which is produced by chromatic aberration. If the wearer doesn't experience the phenomenon with contact lenses, but does with a low-Abbe spectacle lens material like polycarbonate, I think it would be a relatively safe assumption that the spectacle lenses are to blame in this case.
    Darryl J. Meister, ABOM

  15. #15
    Master OptiBoarder
    Join Date
    May 2000
    Location
    PA
    Occupation
    Dispensing Optician
    Posts
    973
    An easy way to verify whether you have a problem with a lower abbe value material is to go back to the phoropter or trial frame the RX. Then you don't have to do trial and error.

  16. #16
    Bad address email on file
    Join Date
    Apr 2005
    Location
    Cambridge UK
    Occupation
    Other Eyecare-Related Field
    Posts
    116
    nothing like good enough! Rx in primary position is irrelelevant.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. high abbe value glasses lenses
    By chris.pickett in forum Ophthalmic Optics
    Replies: 11
    Last Post: 08-08-2005, 02:49 PM
  2. Abbe Value
    By Edgley Gonzaga in forum Ophthalmic Optics
    Replies: 12
    Last Post: 12-02-2002, 12:25 PM
  3. Depth Perception
    By Joann Raytar in forum Ophthalmic Optics
    Replies: 2
    Last Post: 07-07-2002, 08:56 AM
  4. More on Chromatic Aberration and Poly
    By Alan W in forum General Optics and Eyecare Discussion Forum
    Replies: 2
    Last Post: 04-13-2001, 08:22 AM
  5. plastic vs. glass and the burden of prism affects
    By beta chem in forum General Optics and Eyecare Discussion Forum
    Replies: 39
    Last Post: 09-25-2000, 07:13 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
OptiBoard is proudly sponsored by:
Younger Optics and Vision Equipment