filters: series 8 threaded = 67 mm

A while back I asked about going from a threaded series VII to metric. Someone replied that he thought series 8 is the same as 67 mm. I can indeed confirm this: a female threaded series VIII adapter accepts 67 mm filters just fine. This is good because 67 mm is one of my standard sizes ... Anyway, if you have series VI or VII, and if you can find a step-up ring to a threaded VIII, you can use 67 mm filters. (Please note that the second "if" is not necessarily trivial: after 3 months of searching the used bins of photo stores, one came up on Adorama. Two months later it actually arrived.) The logic of the series filter still escapes me, but then, lots of things do.

Series sizes must have had a reason at one time but the logic of them escapes me. I have a Leitz 90mm Elmar-C lens that takes (I think) Series 5.5 filters. Now, the fact is a 39mm filter will fit the lens well enough to use so I don't sweat it. But how many lenses were ever made that took a Series 5.5 filter? And, since 39mm is a standard filter size for many Leitz lenses, whatever possessed them to come up with a filter size that is "almost" 39mm?

Some things truly are mind boggling.

Series filters do not have threaded rims. They are attached via adapters that either slip over or screw onto the lens. They are a lifesaver (or should I say wallet saver) if you use a lot of different filters and need a lot of sizes. It's too bad they have pretty much fallen out of favor in all but series 9. Most people now use a couple of filter sizes and stepping rings, but there was a time when things such as filter threads weren't so standardized. I have a boatload in series 6, 7, and 8 filters that I use regularly.

Bob is correct about series filters. They are threadless and are held in place with a retaining ring. The threads Dave and Lee are talking about are the thread sizes for retaining rings that hold the smooth series filter mounts in place, but can also be used to mount the threaded filters mentioned in these particular cases.

Lee, the companion lens to your 90mm Elmar-C, the 40mm Summicron-C also takes series 5.5 filters, so in that case, you had only one set of filters needed for your CL kit with the 40 and 90. You can still order many B&W filters in this size.

My 24mm Elmarit-R also takes series filters, and the lens shade incorporates a serrated edge dial with an O-ring that is used to spin the filter inside the rectangular lens shade, great for polarizer use.

I think it would have been better for the series filters to have prevailed among camera makers because there probably would have been fewer sizes made and either adapters made or lenses built with fewer "standard" sizes being necessary. Look at the 49mm, 52mm, 55mm differentiation, three mm per "step" in the most common prime lens sizes, a total 3mm radius difference at steps of 1.5mm in radius between nearly all major 35mm SLR brands. Silly when you think about it, and your dealer has to stock a full set in all three. Guess why Cokin saw a market...

Lee