What Noise Does

Topics Covered: Noise Signal-to-Noise Ratio Noise proves nothing. Often a hen who has merely laid an egg cackles as if she laid an asteroid – Mark Twain “Noise is always unwanted,” declared Dr. Optoglass. “But sometimes it fools us into thinking its existence is warranted.” “I see you are not a believer in noise, Dr. […]

At the Edge of Acutance

Topics Covered: Acutance or Edge contrast Local contrast vs Global contrast People see only what they are prepared to see – Ralph Waldo Emerson “Yes, the eye can be cheated,” sighed Dr. Optoglass. “You’ll find visual tricks everywhere, so I don’t have to convince you of that. Sometimes the eye makes something look worse than […]

The World of Contrasts

Topics Covered: What is Contrast? Contrast Ratio and Dynamic Range Contrast is what makes photography interesting – Conrad Hall “You like boundaries and edges, don’t you?” quizzed Dr. Optoglass. He can see through me, thought Bob. “They are interesting, I guess.” “More than that, my dear boy. They are absolutely necessary. Did you wonder why […]

Defining Sharpness

Topics Covered: Defining sharpness Visual Acuity The Snellen Chart Dr. Optoglass opened a drawer, and removed a scalpel. “Okay, Bob. How sharp is this knife?” Bob examines the scalpel. “Pretty sharp.” “Would you say it is sharp enough to cut your finger?” “Sure.” “I’ve got a quotation for you:” I believe there’s nothing more disturbing […]