Compare proportions with a unit
See this course’s project requirements
A pencil or digital three-object still life with measured proportions, negative-space checks, a five-value scale and a before/after correction.
Keep your working files in your own notebook or software. Save a private description, checklist, and work link in My Proof.
What to include
- Produce a three-object block-in and final line/value drawing.
- Record a reference unit and at least two proportion comparisons.
- Check negative spaces with identified edges.
- Include five distinguishable values and a stated light direction.
- Show one before/after correction and an intentional-style note if needed.
Review and revise
Use these criteria to check your work and choose what to improve.
- Observation: large shapes and relative dimensions follow the chosen reference.
- Placement: identified gaps/overlaps are coherent.
- Value: marks support the stated light/form model.
- Revision: one specific correction has independent evidence.
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The idea in everyday life
Choose one visible length and compare the others with it. On paper, you can use a pencil held at a consistent position or simply the supplied coordinate values. Absolute scale may change while ratios remain the same. Use small corrective marks before darkening outlines; no measuring hardware is required.
A ratio can expose a plausible-looking shape error.
Compare proportions with a unit — worked practice
A ratio can expose a plausible-looking shape error.
Take cup width 80 as one unit. Cup height 120 is 1.5 units; box front width 100 is 1.25 units; ball diameter 70 is 0.875 units. If your cup is drawn 40 mm wide, the matched height is 60 mm, box front width 50 mm and ball diameter 35 mm. A 45 mm-tall cup is too squat relative to this reference, although it might be a valid different cup.
1. 2.1 Compare
Record the unit key “cup width 80=1 unit”. Divide each supplied comparison length by 80, writing the dimension associated with every ratio.
You should see: The ratios retain their named dimensions.
2. 2.2 Compare
Choose a drawing cup width of 40 mm or another convenient size. Multiply that chosen length by each ratio to determine the corresponding marks.
You should see: At 40 mm width, cup height 60 mm.
3. 2.3 Compare
Compare your block-in with the computed widths/heights. Use a light corrected boundary before committing to a dark line.
You should see: A squat outline is corrected before shading.
4. 2.4 Compare
Change the chosen cup width to 32 mm and calculate the new height. Explain why the object proportions remain constant even though the picture becomes smaller.
You should see: At 32 mm width, cup height 48 mm.
What to finish
A proportion ledger and corrected block-in.
Watch for this
Measuring each object at a different viewing distance or changing scale for only one dimension.
How can I tell I understand it?
You can resize the whole study while preserving supplied ratios.
Quick knowledge check
Answer all 3 questions. Get at least 2 right and the lesson completes automatically.
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Answer all 3 questions above and get at least 2 right. You can review the explanations and try again.
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Sources and further reading
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Source & access notes · checked 2026-10-01
Read mark-making and observational still-life guidance; original three-object reference and proportion cases supplied here.
Access: Public page text or PDF was opened and read through the web reader on 2026-10-01; no signup required for reading.
Reuse: Linked for further study. All LifeStarter scenarios, samples, assets and assessments are original; no source exercises or artwork are copied.
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