JPEG (JPG)

Check whether learners can explain lossy compression, pixels, JPEG naming, and the limits of JPEG as a manufacturing file.

Sample question: If a JPEG is 2400 pixels wide and printed 12 inches wide, what is its effective pixel density? Answer: 200 PPI. Follow-up: does that number alone prove acceptable quality? No; the product and maker specification still matter.

Questions should test application, not memorization alone. A user might calculate 2400 pixels across 12 inches as 200 PPI, then decide whether that passes only after receiving the specific maker's target. Another question can ask whether changing metadata to 300 PPI adds pixels. Correct feedback should make the arithmetic and the limitation visible.

Show sample images; ask learners to identify artifacts, opaque backgrounds, wrong aspect ratio, and insufficient dimensions.

Show paired crops at the same size: one with JPEG ringing around lettering and one clean source-derived export. Ask the learner to point to the artifact and select a source-based correction rather than simply moving a quality slider on the damaged derivative.

Identification questions should use visible samples at the same scale. Ask the learner to mark a compression halo, a cropped safe-area violation, and an opaque background. A comparison image should come from an original or higher-quality source; otherwise the exercise may accidentally teach learners to repair a lossy derivative by simply saving it again.

Present a photograph, transparent logo, embroidery job, and cut-vinyl job; ask which can use JPEG directly and which need another file.

Scenario: a creator uploads a white-background photo but expects the dark shirt to show around the design. The correct response is to identify the opaque background and request an accepted transparent or otherwise appropriate file, not assume white pixels will vanish.

A useful scenario gives the learner a product brief, source JPEG, and proposed output. They must choose whether to accept, re-export, request another file type, or ask the maker for missing requirements. The correct response should vary by scenario; avoid teaching that 'JPEG is always acceptable' or 'JPEG is never acceptable' for physical products.

Ask learners to isolate the likely causes of blur, unexpected rotation, color shifts, and import rejection without changing multiple variables at once.

Scenario: a proof is sideways in one production application but upright in another. Inspect orientation metadata and the two import behaviors first. Rotating and resaving every copy without identifying the cause may make one output correct and another wrong.

Troubleshooting checks should include evidence from more than one stage. For a sideways proof, provide the file's orientation metadata and two viewer results. For a soft print, provide source pixels, final inches, and RIP scaling. The learner should identify the most informative next test before choosing a fix.