Sunglasses Lens Information

Sunglass Lens Categories, LTF & Absorption Levels

When you order a pair of prescription sunglasses from Spex4Less, we manufacture them to a Category 3 level as standard. This typical sunglass level protects your eyes from bright sunlight and is suitable for daytime driving. Below is a description for each sunglasses category along with their respective LTF (Light Transmission Factor) and light absorption levels. If you require Category 0, 1, 2, or 4 lenses, you will need to place a special order via our helpline.

Sunglass Lens Colours

Mirror Coatings

Mirrored sunglass lenses are also available made to your prescription. They can help to reduce glare but the main benefit is the lens aesthetics.

Currently, we offer Grey with Silver Mirror, Brown with Gold Mirror, Grey with Blue Mirror, and Grey with Fire Red Mirror.

Polarised Lenses

Polarised lenses are available in Grey and Brown and at first glance appear to be regular Grey or Brown sunglass lenses. However, they also contain a polarising filter.

Light which is reflected from a flat surface such as a wet road or water becomes horizontally polarised. This horizontally polarised light is blocked by the polarising filter in the lens which dramatically reduces the glare from these reflections.

Polarised lenses are ideal for Fishing, Sailing, Golf, and general use. However, those that also need to use LCD screens whilst wearing their sunglasses will find polarised lenses more of a hindrance. This is because screens of this nature emit polarised light which is blocked by the filter in the lenses making the screen difficult if not impossible to view through polarised lenses.

Photochromic Lenses

In the presence of UV, a chemical reaction occurs inside a Photochromic lens which turns the lens darker. We offer standard Grey and Brown Photochromic lenses. They are clear indoors but outside in the presence of UV they turn into a darker sunglass lens. This offers you the correct amount of protection for the various light conditions; the more UV they receive, the darker they go.

Unfortunately, because Photochromic lenses require UV to react, they do not work well when used behind a car windscreen. This is because most windscreens today have a UV filter inside them which prevents the UV from reaching your lenses.

However, Transitions have created a lens called Transitions Xtractive. These are almost completely clear indoors (a very pale tint) but react to approximately 50% behind a car windscreen. Outdoors, in the presence of UV, they react to a full dark sunglass tint.

Drivewear Lenses

Drivewear lenses combine both Photochromic and Polarising lens technology. Indoors and in low light conditions, they remain yellow in colour. In medium light and behind a car windscreen, they react to a copper colour. Outdoors in bright sunlight, the reaction continues and the lenses turn to a dark brown colour. Drivewear lenses also contain a polarised filter to reduce reflections, just as a standard polarised lens does.

Wraparound Lenses

Our in-house glazing laboratory is able to glaze high base prescription lenses and wraparound frames. This means that wraparound sunglasses are now available to those who require prescription lenses. Wraparound frames are only suitable for prescriptions within the combined sphere (sph) and cylinder (cyl) power range of -4.00 to +6.00. We will let you know if the combined prescription you have entered falls outside of the acceptable range.