Where can one find small filters? I am looking at my old Tessar and the threaded ring measures 30mm across. They must be out there somewhere.
Where can one find small filters? I am looking at my old Tessar and the threaded ring measures 30mm across. They must be out there somewhere.
eBay.
How old is it? What camera is it on? Most cameras from the 1950's and older used slip-on filters, and the thread was only for the front element retaining ring, so screw-in filters might not fit (depending on the thread pitch).
Either 30 x 0.75 mm screw-in or 32 mm slip-on?
As you can see here screw-in filters are still aviable from 19 x 0.5 mm up to 127 x 0.75 mm.
Peter K is right to remember us that the Heliopan catalogue is a True Ali Baba Treasure Cave, but there exist another thread, very close to 30 mm, namely M30.5x0.5 which I use routinely on my Rollei-35 camera. But this is a fairly recent camera...
For an inside (female) thread, usually what you measure is close to the nominal diameter minus the thread pitch. So I would expect to measure something like 30 - 0.75 = 29.25mm for a M30x0.75, and I would expect to measure 30.5 - 0.5 = about 30 mm for a M30.5x0.5
There exist some cheap comb-shaped thread gages that costs a few dollars
http://www.finelinehair.com/home/thr...g_metric_2.jpg
and that are very helpful to distinguish between a thread pitch of 0.5 and 0.75, among the most common thread pitches for filters of diameters smaller than ~ 80mm.
My Tessar is from 1903.
Heliopa make filters down to 19mm.
Check out this site: http://www.camerafilters.com/default.aspx . Hopefully you can find a step-up adapter to a common size.
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