Image Processing & Enhancement Flashcards

What is the primary purpose of applying a 'high-pass' filter before sharpening via the overlay method?

Answer: It isolates edge detail by removing low-frequency tones, which are then boosted by Overlay mode

The high-pass filter retains only high-frequency edge information as a neutral-gray layer; when set to Overlay, only the edges are sharpened while flat areas remain unaffected.

In focus stacking for macro photography, source images should be captured from:

Answer: Incremental focus distances covering front-to-back depth of the subject

Focus stacking merges images taken at sequential focus distances, each sharp at a different depth plane, resulting in a composite with full front-to-back sharpness.

Which color space uses a perceptually uniform model where equal numerical distances correspond to equal perceived color differences?

Answer: CIELAB (L*a*b*)

CIELAB was designed to be perceptually uniform, meaning a distance of ΔE between two color points corresponds to a consistent perceived difference regardless of the hue.

When correcting chromatic aberration (color fringing) in post-processing, which type requires adjusting the relative magnification of color channels rather than just hue?

Answer: Lateral (transverse) chromatic aberration

Lateral CA causes color channels to be magnified differently, placing them at slightly different positions, so correction requires scaling channels to realign them spatially.

A retoucher notices that healing brush results on a face show smeared texture from a distant skin area. The best corrective action is to:

Answer: Sample from a closer area with similar texture and lighting direction

Sampling from a nearby area with matching texture scale and lighting minimizes the texture mismatch that causes smearing in the healed result.

The 'Protect Tones' option in Photoshop's Dodge and Burn tools is designed to:

Answer: Preserve the saturation and hue of affected areas while adjusting exposure

Protect Tones minimizes hue shifts and saturation changes when dodging or burning, keeping skin and other colored areas looking natural as they are brightened or darkened.

Which image interpolation algorithm is generally recommended when significantly enlarging an image because it considers the surrounding pixel neighborhood to minimize staircase artifacts?

Answer: Bicubic smoother

Bicubic Smoother uses a 16-pixel neighborhood and applies a smooth curve interpolation that reduces jagged edges and aliasing when upscaling an image.