I think "doesn't exist" might be an overstatement. Very rare and
probably old might be a better choice. From Wiki on photo filters:
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Filter sizes and mountings
*Manufacturers of lenses and filters have standardized* on several
different sets of sizes over the years.
Threaded round filters
The most common standard filter sizes for circular filters include 30.5
mm, 37 mm, 40.5 mm, 43 mm, 46 mm, 49 mm, 52 mm, 55 mm, 58 mm, 62 mm, 67
mm, 72 mm, 77 mm, 82 mm, 86 mm, 95 mm, 112 mm and 127 mm. Other filter
sizes within this range may be hard to find since the filter size may be
non-standard or may be rarely used on camera lenses
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My guess is that the set of filter sizes is what was in common use by
manufacturers already when the standards were decided.
Chuck Norcutt
On 8/28/2015 8:58 AM, John Hudson wrote:
Volume 24 of the Canadian "Photo News" magazine carries an article part
of which reads:
"One more number should be found on your lens. It is usually preceded or
followed by the symbol Ø. It is the size of the filter needed for that
lens. So, on a 50mm lens the filter size will /*never*/ [sic] be 50mm ,
as this filter size doesn't exist. Most likely, you will find a Ø52 or a
Ø49."
Question: why no 50mm filter size?
I have done an extensive google search and have not found an answer.
jh
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