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Lenses

What the lens is doing: polarisation, UV, tint, coatings, categories and materials. The physics, in plain language, and what each property does and does not change.

The view from a high-altitude cockpit window over a blinding white cloud deck under deep blue sky

Lenses · September 30, 2026 · 3 min Why pilots do not wear polarized sunglasses, and what they wear instead Polarized lenses can hide the glint off another aircraft, black out LCD instruments, and show stress patterns in a laminated windscreen. The FAA advises against them in the cockpit. What pilots wear instead is a non-polarized neutral grey with strong UV blocking and a thin-armed frame that fits under a headset. Here is the reasoning, and what it means for anyone who reads screens in bright light.

A shopping mall atrium flooded with skylight, a polished floor reflecting the glass roof, no people

Lenses · September 30, 2026 · 4 min Is wearing sunglasses indoors bad for your eyes? What actually happens Wearing sunglasses indoors does not damage your eyes. The one real effect is that your eyes adapt to the dimness, so bright light feels harsher when you take them off. There are good reasons to wear them inside: migraine, light sensitivity, recovery from eye surgery. Here is what is true and what is myth.

A high mountain ridge under a hard pale sky, intense sun on rock and snow

Lenses · September 30, 2026 · 4 min UV400 vs polarized: they are not the same thing, and you want both UV400 and polarized describe two different properties. UV400 is about protecting your eyes from ultraviolet light. Polarized is about removing glare. A lens can be either, both or neither. Here is how to read the labels and what to check.

Three clear lens blanks on black velvet under a single light, each catching a different highlight

Lenses · September 30, 2026 · 4 min Sunglasses lens materials: glass, polycarbonate, TAC and CR-39, compared honestly Four materials make almost every sunglasses lens. Glass is the clearest and scratches least but is heavy and can shatter. Polycarbonate is the toughest. TAC is light, cheap and the usual home of a laminated polarizing film. CR-39 sits between. Here is what each does well, what it does badly, and how to tell which you have.

Extreme close-up of water beading into spheres on a glossy hydrophobic surface against a dark background

Lenses · September 30, 2026 · 4 min Sunglasses lens coatings explained: hard coat, anti-reflective, hydrophobic and mirror A modern sunglass lens is a stack. On top of the tinted lens sit up to four coatings, each doing one job: a hard coat against scratches, an anti-reflective layer on the back to stop light bouncing into your eye, a hydrophobic layer to shed water and smudges, and sometimes a mirror on the front. Here is what each does, which ones are worth paying for, and which you cannot see.

Five squares of grey glass on a lightbox stepping evenly from almost clear to nearly black

Lenses · September 30, 2026 · 4 min Sunglasses lens categories and VLT: what category 3 means and why it is not a UV rating Lens categories 0 to 4 describe how dark a lens is, measured as visible light transmission, the percentage of visible light that passes through. Category 3 is the everyday sunglasses band. Category 4 is too dark for driving. None of it says anything about UV protection or polarization.

Small sheets of acetate in tortoiseshell, black and clear stacked on a workbench beside a bar of matte nylon

Lenses · September 30, 2026 · 4 min Sunglasses frame materials: acetate, injected plastic, TR90, nylon and metal, compared honestly The frame decides weight, flex, how it survives being sat on, and whether it can be adjusted. Acetate is the premium plastic, cut from sheet and polished. Injected plastic is cheaper and lighter. TR90 and nylon flex without breaking. Metal adjusts and lasts but weighs more and corrodes near salt. Here is what each is, what it costs you, and how to tell which you have.

A wooden garden bench in strong midday sun with slats casting sharp shadows on dry grass

Lenses · September 30, 2026 · 4 min Do sunglasses block vitamin D? No. Your skin makes it, not your eyes Vitamin D is made in the skin when UVB light reaches it. The eyes play no part. Sunglasses block UV reaching the eye, which is exactly what they should do, and have no effect on how much vitamin D your skin makes. Here is where the myth came from and what actually decides your vitamin D.

Five sheets of tinted glass in a row, grey, brown, deep blue, pale blue and red-orange, each casting a coloured shadow

Lenses · September 30, 2026 · 5 min Sunglass lens colour guide: what grey, brown, blue, ice blue and red each do to the light Every lens colour edits the light differently. Grey dims evenly, brown lifts contrast, and mirrors turn away a slice of light before it reaches the tint. Here is what each of the five common tints does, and which light it is for.

A wet road in low sun throwing a sheet of white glare toward the camera

Lenses · September 30, 2026 · 5 min Polarized vs non-polarized sunglasses: what the filter actually changes Polarized and non-polarized sunglasses can be equally dark and equally UV-safe. The difference is glare. Here is what a polarizing filter removes, when it matters, when it gets in the way, and how to tell which you own.

A smartphone lying face up on a car dashboard in direct sun with a faint rainbow sheen on its dark screen

Lenses · September 30, 2026 · 4 min Why polarized sunglasses make your phone screen go dark or rainbow Polarized sunglasses can make a phone, car display or fuel pump screen go dark, dim or show rainbow bands. The screen is not broken and neither are the glasses. Here is what is happening and the three ways around it.

A country lane seen from a doorway, half in bright sun and half in the shade of a porch, with a hard light line across the path

Lenses · September 30, 2026 · 4 min Photochromic vs polarized sunglasses: one changes darkness, the other removes glare Photochromic lenses darken in UV light and lighten without it. Polarized lenses remove reflected glare at a fixed darkness. They solve different problems and can be combined. Here is what each does, how fast photochromic really changes, and why it does not darken in a car.

Extreme close-up of a curved mirrored surface reflecting a beach and sky

Lenses · September 30, 2026 · 4 min Mirrored vs polarized sunglasses: one is a coating, the other is a filter Mirrored and polarized are not alternatives. A mirror is a reflective coating on the outside of the lens that turns away some light before it enters. Polarization is a film inside the lens that removes reflected glare. A lens can be either, both or neither, and the two do different jobs.

A still lake at midday with the sun reflected as a blinding streak across the surface

Lenses · September 30, 2026 · 4 min How to tell if sunglasses are polarized: three tests that take a minute You can check whether any pair of sunglasses is polarized in under a minute with a phone screen, a second pair of sunglasses, or a window in daylight. Here is how each test works and what it will and will not tell you.

A flat sea horizon at midday, the sky deep blue at the top of the frame grading to pale white at the water

Lenses · September 30, 2026 · 4 min Gradient lenses explained: dark at the top, light at the bottom, and who that actually suits A gradient lens is darker at the top than the bottom. The idea is sun from above, a clear view of the dashboard or a book below. It works for driving and reading and fails on water, snow and any surface that throws light up from below. Here is what gradient does, how it differs from photochromic, and whether it can be polarized.

A laptop screen glowing cool blue-white in a dark room at night, light spilling across a desk

Lenses · September 30, 2026 · 4 min Do sunglasses block blue light? Yes, some of it, and here is which tints block most Every tinted lens reduces blue light, because blue is part of visible light and a tint dims visible light. Brown, amber and yellow tints remove more blue than grey. What sunglasses are not is a fix for screens at night, where the issue is brightness and timing rather than a wavelength. Here is what the evidence supports.

A polished walnut desk with a brass magnifying glass, an old leather ledger and round smoked-glass lens blanks in a wooden tray

Lenses · September 30, 2026 · 5 min A short history of sunglasses: from Inuit slit goggles to the polarizing film Sunglasses are older than glass lenses. Arctic peoples cut slits in bone and wood to beat snow glare thousands of years ago. Smoky quartz shaded Chinese judges' eyes in the twelfth century. Tinted spectacles were a medical curiosity until the 1920s, when mass production, Hollywood and aviation made them an object. The polarizing film came in 1936. Here is the line from there to the lens on your face.