master test C
hina’s optical industry has progressed beyond rec- ognition, as anyone who has bought a ‘Gorilla glass’ type cover for their camera screen will know. Top grade Schott and Hoya glass is being turned into affordable accessories at prices well below historic highs. When one brand tries to sell you a variable neutral density (crossed slimline polariser) filter for around £200, an apparently identical prodict at £40 raises suspicions of inferior quality. That just isn’t so any more. SRB Photographic has sourced a new range of multi- coated, very slim, optically plane filters under their own brand. Initially these are a UV protec- tor, a circular polariser and a variable neutral density which covers from 2 to 8 stops. The polariser is of the low optical density type, with very neutral colour, first introduced by Hoya. The variable ND with its rotating wide-angle mount (in our example, 77mm lens thread and 82mm front thread) consists of two polarisers of this grade in a very smooth and well finished metal rim. The markings from Max to Min are useful but hard to see from a behind the camera position.
I tested it on a waterfall and river – 30 seconds for Roughting Linn, top, and 20 seconds for the Tweed in spate. General quality is high but it must be shielded from direct into-the-sun conditions, and it’s important not to use values close to maximum with wide- angle lenses or you will see patchy zones of darkening (from 28mm or wider). Values around 5-6 stops have even ND. There’s no discernible colour shift, and with my ƒ2 and ƒ2.8 lenses, AF worked well at minimum density, followed by locking focus at MF then rotating until the desired exposure was produced. – David Kilpatrick
See:
www.srb-griturn.com MASTER PHOTOGRAPHY 21
photography SRB Photographic Hd filters and variable ND
The SRB Hd filters are packed in a similar clamshell plastic to Hoya or Kenko. The adaptor rings, front, are inexpensive and allowed me to use 77mm filters with several different lenses to test them.
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