37.5mm threads, 37mm filter, adapter needed?

January 4, 2011 3:09 PM

Just a quick dumb question I can't find answered anywhere else: I have a videocamera with 37.5mm lens threads. A filter I want to buy online has 37mm threads (and that spec seem more common in general). There's a 37.5mm-to-37mm stepdown ring available elsewhere, but it costs twice as much as the filter. Is that 0.5mm really enough to need the stepping ring?
posted by AzraelBrown to media & arts (6 answers total)

I cut threads in metal for a living. Yes, .5mm is a very significant difference, especially if you don't want to damage the threads on your video camera lens.
posted by TrialByMedia at 3:16 PM on January 4, 2011 [1 favorite]

0.5mm is big enough that the filter will fall out unless you do something to hold it in there, but small enough that you might get away with wrapping the thread in electrical tape and jamming it in there.
posted by Mike1024 at 3:23 PM on January 4, 2011

As someone who has also cut threads for a living I'll agree with TrialByMedia; yes, 0.5mm is enough to need a stepping ring. As someone who has baulked at buying or making adaptors (particularly for non-critical applications), I'll also agree with Mike1024: taping the thread would probably do the trick.

But electrical tape is almost certainly too thick. Most is 7 mil (~0.2mm) thick, plus glue. Double that (i.e. 1 layer on either side of your circumference) is 0.4mm (+ 2 lots of glue) - uncomfortably close to 0.5mm (and, with glue, probably more than 0.5mm), and that's not even accounting for the cut of the thread. Teflon thread tape would be a better idea, at ~0.1mm thick with no glue.
posted by Pinback at 5:26 PM on January 4, 2011 [2 favorites]

Just chiming in to note that Teflon thread tape is available in the plumbing section of the hardware store (or the Home Depot or whatever).
posted by box at 6:10 PM on January 4, 2011

You need the adapter.
posted by gatsby died at 8:57 PM on January 4, 2011

Or a filter that is the right thread.
posted by gatsby died at 8:57 PM on January 4, 2011