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Coma of a single lens. Each cone of light focuses on different planes along the optical axis. In optics (especially telescopes), the coma (/ ˈ k oʊ m ə /), or comatic aberration, in an optical system refers to aberration inherent to certain optical designs or due to imperfection in the lens or other components that results in off-axis point sources such as stars appearing distorted ...
In most cases, two thin lenses are combined, one of which has just so strong a positive aberration (under-correction, vide supra) as the other a negative; the first must be a positive lens and the second a negative lens; the powers, however: may differ, so that the desired effect of the lens is maintained. It is generally an advantage to secure ...
Ironically, the two groups in a Petzval portrait lens are primarily intended to control spherical aberration and coma, but actually make field curvature worse. This tradeoff was desirable because for a long focus lens better correction of spherical aberration and coma permits a faster aperture setting, which is more important than any defect of ...
For example, if it is known that a lens DoF scale is based on a CoC of 0.035 mm, and the actual conditions require a CoC of 0.025 mm, the CoC must be decreased by a factor of 0.035 / 0.025 = 1.4; this can be accomplished by increasing the f-number determined from the DoF scale by the same factor, or about 1 stop, so the lens can simply be ...
It is in this lens shape that the mechanically reproducible state of a steep radius of curvature in the center of the lens with slight flattening of the peripheral anterior lens, i.e. the shape, in cross section, of a catenary occurs. The anterior capsule and the zonule form a trampoline shape or hammock shaped surface that is totally ...
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The Maddox rod is a handheld instrument composed of red parallel plano convex cylinder lens, which refracts light rays so that a point source of light is seen as a line or streak of light. [2] Due to the optical properties, the streak of light is seen perpendicular to the axis of the cylinder.