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HOYA FILTERS

Polarising paradise Thanks to its eight coatings and slim profile, the new Revo circular polariser fromHoya could be the filter to bag

TOP RIGHT On a clear day, especially when the sun is high, a polarising filter can enhance a blue sky. RIGHT No filter.

The Hoya Corporation is the world’s largest manufacturer of optical glass. Hoya filtershave long been the choice of professional photographers, and the renowned Pro-1 range is both extensive and high quality. More recently, Hoya introduced the premier HD series with extra-toughened glass and highest grade multi-coating, and now the Revo slots in between Pro-1 and HD. Top of the Revo range is the landscaper’s favourite, the ever-popular circular polarising filter. Revo incorporates not only the finest optical performance, but also top grade multi-coating with an additional protective layer, making the filters less prone to marking and easier to clean. Revo protective layer The new Revo’s hard outer protective coating is both water and stain resistant. As the comparison pictures, right, show, regular multi-coated filters can be damaged by rain allowed to dry on the surface. On the normal filter water drops spread into blobs, whereas on the Revo they form beads that run off. Dried-on watermarks are extremely difficult to remove from an ordinary multi-coated filter, often impossible. With Revo, these marks come straight off, including dried-on salt sea spray, and this is a major advantage in situations where you really need a protection filter to do its job. To test the toughness, we tried scratching the Revo’s surface with the sharp end of a paper clip, pressing hard

enough to bend the metal, but amazingly, the filter was completely unmarked. Impressive.

Why multi-coating? When light strikes a glass surface, about 4% is reflected, and the same amount again when it passes through the other side – a total of 8%. This loss of light is obviously not a good thing, but also when reflected light gets inside a lens it bounces around and some finds its way to the sensor, causing flare and ghosting. Coating the glass surface reduces reflectance dramatically and typically a single-layer coating will cut reflections in half. Hoya’s SMC Super Multi- Coating goes further still, with up to eight furnace- bonded layers, raising light transmission to 99.35%. Slim, low-profile mount With very wide-angle lenses, it’s sometimes possible for a standard thickness filter to encroach into the corners of the image. The Revo’s slim low-profile mount prevents this, but Hoya has still found room to include front threads, so a second filter and a clip-on lens cap can be attached. The Hoya Revo range of circular polarisers, UV filters and clear protection filters represents the highest quality available and comes thoroughly recommended. Sizes range from 37 to 82mm, with guide prices from £43.

To test the toughness, we tried scratching the Revo’s surface with a paper clip, but it was completelyunmarked

ABOVE LEFT Hoya Revo filters have a tough and water-resistant coating. Droplets form into beads and dried-on marks are easy to clean. ABOVE RIGHT With ordinary multi-coated filters, droplets tend to form blobs and dried-on watermarks are very difficult or even impossible to remove, leaving silvery outlines.

Reducingpolarisedreflections

Reflections are polarised (all except those off bare metal) and at the optimum angle and correct degree of filter rotation, they can be greatly reduced or eliminated. The best angle is between 30 and 40° to the surface, known as Brewster’s Angle, and this usually falls nicely for reflections off water so you can see beneath the surface. And with motorsport, this angle can cut reflections off windscreens, so you can see the driver. In both these cases, the optimum degree of rotation will have the index mark around the top, so blue skies get darkened at the same time. It is the two combined effects of a polarising filter – blue skies and reduced reflections – that makes them the landscaper’s favourite. With leaves, grass and foliage, there are almost always some shiny reflections off the surfaces and at least a few of those will naturally fall at Brewster’s Angle, so the filter makes colours richer and more saturated. Be careful with pictures of people, especially on the beach. A polariser can take the attractive sheen off a suntan, turning skin to putty.

ABOVE LEFT A polariser darkens blue skies and cuts reflections from leaves and foliage, enhancing the colour. ABOVE RIGHT No filter.

To find out more go to www.intro2020.co.uk

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