Why do PNG photographs become much smaller as JPEG but logos may not?
JPEG's DCT compression excels on smooth tonal regions (skin, sky, gradients) and struggles on sharp edges and flat color regions (text, UI, logos). A 2 MB PNG photograph often becomes 200–400 KB JPEG at Q80 with imperceptible change. A 200 KB PNG logo with transparency may become 180 KB JPEG at the same quality while looking worse near edges — keep logos as PNG or WebP with alpha. Rule: PNG→JPEG for camera photos and textures; keep PNG for brand marks, screenshots with text, and any asset needing transparency.