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Old 11-06-2016, 09:14 AM
gregbradley's Avatar
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gregbradley is offline
Join Date: Feb 2006
Location: Sydney
Posts: 15,473
Its either dust on the filter or a defect in the coating.

Try cleaning it with a photographic cloth and using a bright torch illuminating the filter at an angle to show up any dust particles and see if it changes anything.

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