Re: Seated in Grass: Comments on individual versions

Robert Wheeler

I'll bet your brightening was not actually applied just to to the "pupil." Apology in advance for being picky, but my medical background makes it hard for me to resist commenting. Quick eye anatomy review: the black circle in the center of the eye is an opening for light to enter after being partly focused by the transparent cornea and before being focused by the transparent lens (for subsequent detection by the light sensitive cells in the retina at the back of the eye). That black opening is known as the pupil. It serves as a variable aperture that gets bigger to let in more light in dark environments and smaller to let in less light in bright environments.

The colored area around the pupil is the iris, which is the part that actually expands or contracts to make the pupil change size. When we talk of blue or green or brown "eyes," we are referencing the iris.

in front of both the pupil and the iris we have a transparent cornea. Around the iris, the cornea merges with the visible part of the sclera, generally known as the white of the eye. Trivia note: a few people with rare metabolic conditions can have blue sclerae even with correct color balance.

So a healthy eye has a black pupil (aside from "red eye" reflections off the retina caused by on-axis flash). If area of the pupil is grey or white, it can indicate scaring or disease of the cornea, a dense lens (cataract, sometimes removed surgically and replaced with an artificial lens), or even a tumor inside the eye (retinoblastomas sometimes are first detected as white pupil areas in newborn photos), or maybe a specular reflection of a light. So we would not want to brighten the black pupil, as that could make the eye look abnormal. However, the iris, sclera, and sometimes lids are often targets for appropriate adjustments.

Robert Wheeler

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