chromatic aberration

(noun)

an optical aberration, in which an image has colored fringes, caused by differential refraction of light of different wavelengths

Related Terms

Examples of chromatic aberration in the following topics:

  • Combinations of Lenses

    • The use of multiple elements allows for the correction of more optical aberrations, such as the chromatic aberration caused by the wavelength-dependent index of refraction in glass, than is possible using a single lens.
    • An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic and spherical aberration.
    • The lens elements are mounted next to each other, often cemented together, and shaped so that the chromatic aberration of one is counterbalanced by that of the other.
    • (a) Chromatic aberration is caused by the dependence of a lens's index of refraction on color (wavelength).
    • (b) Multiple-lens systems, such as this achromatic doublet, can partially correct chromatic aberrations, but they may require lenses of different materials and add to the expense of optical systems such as cameras.

  • Aberrations

    • A chromatic aberration, also called achromatism or chromatic distortion, is a distortion of colors .
    • Since the index of refraction of lenses depends on color or wavelength, images are produced at different places and with different magnifications for different colors. shows chromatic aberration for a single convex lens.
    • A comatic aberration, or coma, occurs when the object is off-center.
    • These aberrations can cause objects to appear pear-shaped.
    • Spherical aberrations are a form of aberration where rays converging from the outer edges of a lens converge to a focus closer to the lens, and rays closer to the axis focus further.

  • The Compound Microscope

    • The advantages of these microscopes, due to the multiple lenses, are the reduced chromatic aberrations and exchangeable objective lenses to adjust magnification.

  • The Telescope

    • The potential advantages of using mirrors instead of lenses were a reduction in spherical aberrations and the elimination of chromatic aberrations.
    • With the invention of achromatic lenses in 1733, color aberrations were partially corrected, and shorter, more functional refracting telescopes could be constructed.

  • Scales and Western Music

    • In the chromatic scale, every interval is a half step.
    • Listen to a chromatic scale: http://cnx.org/content/m11636/latest/Chromatic.MID.
    • In both the chromatic and the whole tone scales, all the intervals are the same.
    • There is basically only one chromatic scale; you can start it on any note, but the pitches will end up being the same as the pitches in any other chromatic scale.
    • The chromatic scale includes all the pitches normally found in Western music.

  • Half Steps and Whole Steps

    • So a scale that goes up or down by half steps, a chromatic scale, plays all the notes on both the white and black keys of a piano.
    • (A few instruments, like trombone and violin, can easily play pitches that aren't in the chromatic scale, but even they usually don't. )
    • A whole tone scale, a scale made only of whole steps, sounds very different from a chromatic scale.
    • If you have trouble keeping track of the notes, use a piano keyboard, a written chromatic scale, or the chromatic fingerings for your instrument to count half steps.
    • All intervals in a chromatic scale are half steps.

  • Hybrid Themes

    • And these chords are usually chromatic alterations of chords native to the present key.
    • The chromatically altered chord will function as a dominant chord in the key of the chord that follows it.
    • The chromatically altered chord will be an alteration of the function that logically precedes the function of the chord that follows it.
    • Like chromatically altered subdominant chords, every applied chord will have two elements to its functional bass symbol.
    • (The square brackets are necessary no matter in which voice the chromatic alteration occurs.)

  • Chromium

    • Most important are the chromate (CrO42-) and dichromate (Cr2O72-) anions, which exist in equilibrium:
    • The change in equilibrium is visible by a change from yellow (chromate) to orange (dichromate), such as when an acid is added to a neutral solution of potassium chromate.
    • Both the chromate and dichromate anions are strong oxidizing reagents at low pH.
    • The oxidation state +5 is only realized in few compounds but are intermediates in many reactions involving oxidations by chromate.

  • Applied Chords

    • And these chords are usually chromatic alterations of chords native to the present key.
    • The chromatically altered chord will function as a dominant chord in the key of the chord that follows it (V or VII).
    • So while F7 may be V/V in E-flat, it is a chromatically altered S, and so belongs in the S harmonic zone.
    • (The square brackets are necessary no matter in which voice the chromatic alteration occurs.)
    • Also as a shortcut, the chromatically raised tone tends to be the leading-tone of the tonicized key.

  • Modal Mixture

    • However, it will usually require a chromatic alteration (flat, natural, sharp, or slash).
    • Chords borrowed from parallel keys are chromatically altered chords, and therefore their functional bass symbols should be enclosed in square brackets.
    • If the bass note is chromatically altered, that must be reflected in the functional bass with a plus or minus before the numeral (as well as the square brackets).
    • (The thoroughbass will also be altered to reflect the chromatic change.)