Small-sized filters?

[Robbie Bedell]

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.

[Vick Vickery]

eBay.

[J. Patric Dahlen]

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).

[Peter K]

Either 30 x 0.75 mm screw-in or 32 mm slip-on?

As you can see here (http://www.heliopan.de/preise.shtml) screw-in filters are still aviable from 19 x 0.5 mm up to 127 x 0.75 mm.

[Emmanuel BIGLER]

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/thread_gages_eng_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.

[Robbie Bedell]

My Tessar is from 1903.

[Bob Salomon]

Heliopa make filters down to 19mm.

[Brian Schall]

Check out this site: http://www.camerafilters.com/default.aspx . Hopefully you can find a step-up adapter to a common size.