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Blurry figures in a printed exam — screenshots, vectors, and how to choose
A screenshot looks fine on screen and prints soft. The difference is raster versus vector, and it decides how long your figure stays usable.
A screen shows about 96 pixels per inch; a laser printer lays ink at 600 to 1200 dots per inch. A screenshot that is just sharp enough on screen is being enlarged six to twelve times on paper, with no extra information to fill the gap.
Why vectors do not have that problem
A vector image stores a description rather than pixels: this segment runs from here to there, this arc has this radius. At print time the printer redraws from that description at its own resolution. One figure serves an A4 worksheet, a projected slide and a wall-sized enlargement without being redrawn.
When a screenshot is still the right choice
A photograph has to be a photograph: an experiment, a specimen, a page of a book. Forcing those into vector makes no sense. What matters there is capturing at high resolution to begin with — 300 dpi at the size it will print — rather than screenshotting and enlarging.
- Geometry, function graphs, variation tables, circuits, reaction schemes → draw as vector.
- Photographs and book scans → raster, but captured at 300 dpi at the printed size.
- A screenshot of a diagram → almost always the wrong choice; that diagram was vector somewhere.
Texva has a canvas per figure type and exports real vector TikZ, so a figure in the paper stays editable stroke by stroke rather than becoming a dead image. The canvas at /graph works without an account if you just need one figure to drop into a document you are writing elsewhere.
Templates for this
- End-of-Term Chemistry Exam (Vietnam)Chemistry final exam with a real molecule diagram and reaction/equation questions.
- Sample: Physics ExamA mechanics exam sample with point values, equation reasoning, rubric, and teacher-only answer key.
More posts
- The twelve question types a THPT paper can use, and what each one measuresThe twelve types do not measure the same thing. What each one is actually good at, the cognitive level it fits, and the mistake each one invites.
- Marking answer sheets from a photo — what to get right before you printMarking from a photo is far faster than by hand, but a mistake in preparation mismarks a whole room with nothing looking wrong. Four things to settle first.
- Writing a Circular 5512 lesson plan faster without dropping sectionsA Circular 5512 lesson plan is long because it must be complete, not because it needs a lot of writing. The four slowest parts, and which of them can go.