NSF certifies drinking water filters to standards applicable to each type of treatment option. You may notice the NSF mark on a product along with numbers such as NSF/ANSI 53 or NSF/ANSI 42, which refer to the standard to which the filter has been certified.
The definition of a canon is a principle, law or standard by which people are judged or a member of the clergy living according to these principles or laws. An example of a canon is a moral principle that a group believes is correct or proper.
Canon 500D Close Focus Filter â A close focus filter is simply a thick filter that screws onto the end of your lens and allows you to focus closer than you would normally be able. I tested this filter on the Nikon 70-200mm lens. Yes, thatâs right. A Canon filter on a Nikon lens.