The opacity scale, and how we score it

Opacity is the single thing photographs lie about most. Studio lighting is set to flatter a garment, not to test it, and a fabric that is perfectly decent under three softboxes can be a different proposition at a bus stop in June.

So we score it, one to five, and the test is deliberately harsh. A single layer of the fabric is held 20cm from a north-facing window at midday over printed text at 12pt. Then the same fabric is photographed on the body with a light source directly behind.

• 5 — opaque in direct light. Wears alone with nothing underneath.
• 4 — opaque in normal daylight; a strong backlight shows the body's outline but no detail.
• 3 — a light layer is sensible in bright sun, or if you are wearing a contrasting colour underneath.
• 2 — sheer. Sold as a layering piece and described as one.
• 1 — we do not sell these.

Two things follow from this. The first is that a 3 is not a failing grade, it is information: the Loom Longline Tunic is a 3 and it is one of the pieces we wear most, over a Second Skin Under-Top. The second is that lining changes the score, so a lined 5 and an unlined 5 are the same promise, made two different ways.

Rate it as it behaves on a bright street, not as it photographs in a studio.

If you ever receive something that does not match its score, tell us. We will re-test the fabric, change the number on the site, and write to everyone who bought it.