Sunglass hinge tension and lens tint
Whether hinge tension is even on both temples and whether the lens tint shifts the colours seen through it.
The reading sequence
4 steps, starting at surface and finish and running to read each tint against white paper in daylight. Evidence on this point is read at E1, and 1 of the 4 steps carries a condition that ends the assessment outright.
Ask for a close video of both temples opening
See whether the two hinges move with the same resistance and stop at the same point in their travel.
Evidence: E1 — one close video of each temple opened and closed slowly three times, taken from above the hinge
- Each temple opens through its full travel without binding at any point.
- A temple released partway open holds the position it was left in.
- Both temples stop at the same angle at the end of their travel.
- One temple moves more freely than the other, with no play when the frame is held.
- A creak on one side that does not repeat on the second pass.
- A temple binds partway and needs a push to continue past that point.
- A hinge screw turns visibly with the temple, showing it is not seated.
Wobble each temple with the frame held at the bridge
Decide whether the hinge plates carry play, which is the failure that shows up as a rattle within weeks of wear.
Evidence: E1 — a short video of the seller holding the frame by the bridge and moving each temple up and down with two fingers
- Neither temple moves at the hinge under light finger pressure.
- The frame front stays rigid while one temple is moved.
- Play of under 1 mm at one hinge, with no rattle and no click.
- The seller presses so lightly that neither hinge is actually loaded.
- A temple moves visibly up and down at the hinge under light pressure.
- The frame front flexes when one temple is moved, showing the front is not rigid.
Fold both temples and compare the resting angle
See whether the folded frame sits flat, which catches a bent temple or a hinge that stops early.
Evidence: E1 — one overhead photo of the folded frame on a flat surface, plus one taken from the side at surface level
- Both temples fold to the same angle and rest against the frame front without crossing.
- The folded frame sits flat, with no corner lifted off the surface.
- A gap of under 2 mm between one temple tip and the frame front.
- The folded frame rocks slightly on the surface with no visible bend in either temple.
- The two temples fold to visibly different angles.
- One temple crosses over the frame front or lifts the folded frame off the surface.
Read each tint against white paper in daylight
Check whether a lens shifts the colour of what is behind it, and whether the two lenses shift it the same way.
Evidence: E1 — one photo per lens of white paper seen through the lens, flat to the paper in shade, plus one photo of the paper alone
- Both lenses show the same paper tone, and that tone is the one the lens colour names.
- The edge of the paper seen through a lens carries no colour fringe.
- The paper alone in the same light is neutral, so the reference is sound.
- A slight difference between the two lenses that disappears when they are swapped in front of the camera.
- A faint gradient from the centre to the edge of one lens.
- The two lenses shift white paper to two different colours.
- A mirror or gradient coating is patchy, with thin areas that change tone across the lens.
Why the thresholds sit where they do
A hinge is the part of a frame that a still photo cannot describe, because a still image records position and not resistance. The first two steps split that question: a slow open and close shows whether travel is even, and a wobble test shows whether the plates are tight in the front. The 1 mm play figure sits below the point at which a frame rattles, which is the stage a wearer actually notices, and above the fraction of a millimetre that any acetate frame shows when new. The tint step is written around a sheet of white paper because the eye adapts to a tint within seconds and then stops reporting it; a reference tone in the same frame takes that adaptation out of the comparison. Each lens is photographed separately because a pair built from two lens batches is common and shows only when the two images are placed side by side.
Common misreads
2 pairs recorded for this point. Each runs in both directions: 1 finding that looks worse than it is, and 1 that looks better.
- looks like Return actually Pass
A lens that turns white paper faintly grey-green in a phone photo. With the paper-only reference beside it, the same cast sits on the paper as well as on the lens, so the camera moved the colour rather than the coating.
- looks like Pass actually Return
A frame photographed open on a table with both hinges looking clean. An open frame puts no load on a hinge, so play and a loose screw cannot be told apart from a hinge that is tight.
Check this point against what you were sent
Insufficient evidence
Nothing decided on sunglasses hinge and lens tint yet: 0 of 4 steps have been read.
0 of 4 steps judged
| Step | Reading | Evidence | Stop met |
|---|---|---|---|
| 1. Ask for a close video of both temples openingneeds E1 | — | ||
| 2. Wobble each temple with the frame held at the bridgeneeds E1 | A hinge shows visible vertical play with the frame held at the bridge. The hinge plates sit loose in the front, and no adjustment a buyer can make at home closes that play. | ||
| 3. Fold both temples and compare the resting angleneeds E1 | — | ||
| 4. Read each tint against white paper in daylightneeds E1 | — |
Sources and checks
- Public community thread — Frame threads where hinge play or tint was raised after deliveryn=36
- Editor analysis — Paper-reference method added after tint disagreements under mixed lightingno sample
Last checked · next review due · status current.
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