I have a 90mm, and a 162mm raptar. I would like to use my Cokin filter holders with both of these, but have no accurate way to determine the size in mm. I know my 52mm adapter ring is too large for my 162mm Raptar, but it is close. I have nothing close to the size for the 90mm. I hope to use the adapter ring as a push on afair for both. I have searched the web high and low, but can find nothing along these lines. Any help would be appreciated.

Jonathan

Use any good ruler with a mm scale, measure the center, from outside edge to outside edge, rounding up to the next mm; 48.4=49.

I know the answer to the question seams obvious, but I tried this with a plastic ruller you can get a WalMart, and bought an adapter ring that was too small. If anyone on the forum knows the exact size, it would be a help.

Thanks
Jonathan

I got either 31.5 or 31mm but 1 1/4 is right on for the 90mm

By good, I meant a stainless steel pocket type with a sliding clip or a venier caliper or simular instrument.
most plastic or wood rulers have a 1 to 1.5mm tolerance not a .25mm . sorry if I was otherwise misleading.

By using a piece of wire to find the cir. and then calculating the diameter with my new circa 1947 K&E Log Log Decitrig Duplex slide rule I just got from you know where I come up with
......... 1.248"

My Starrett 2 inch mic says 1.254"

and my "lens filter" brochure from Kodak circa 1954 says...... "inch anda quarta" (it was from a Brooklyn camera store) :^)

OK, I'll be a little more carefull when asking for specifics in the future. The one thing I did not take into account was the threads on the adapter rings are on the outside, and I need the inside of the adapter ring to slide over the lens. So, when you measure the 162mm Raptar at 45mm, a 46mm adapter ring is too small. I bought a 49mm which is a little bit too large, but with a few bits of tape can be made snug, and now holds the filter holder very well.

As the 90mm Raptar is about 32mm, I think the 36mm adapter ring will work, although I have not tried one yet.

Hope this helps someone else in the future.

Check this link for more info on measuring lens threads, I think it will help.

http://www.skgrimes.com/adapter/measure.htm

A vineer caliper with a metric and inch markings should be available at a local hardware store for $20 or less, verry helpfull if you have several lens to check. Tape only last for a year or two then messy clean up and retape.

Jonathan: something you said got me to wondering...."the threads on the adapter rings are on the outside, and I need the inside of the adapter ring to slide over the lens." The part of the slip ring that slips around the front lens element should be smooth on both sides, with several equally spaced slits to allow a bit of "give" to the diameter when you install and remove it. This is assuming you are using a Kodak slip ring. The other end of the slip ring is threaded on the INSIDE for a retaining ring to hold your filter: these threads are 44mm on the series VI slip ring. Or am I misunderstanding your set-up?

the size is wrong but this is what the beast should look like. This presses on the lens, the filter drops inside it, then either the other ring, a polarizing filter or a lens shade screws on and locks everything together.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1347362986

Henry,

I might be better off using an old fiter ring than what I am trying to do. I am trying to use the Cokin filter holders I have for my 35mm with my Super Graphic. (Economizing) I was trying to find the size of the adapter ring for a Cokin holder to slide on my 90 & 162mm Raptar. This so I didn't have to hunt for the things that were designed for the lens. I've made something that works, maybe not the best, but it is a solution.

With the 49mm adapter ring, I added some tape to the inside, and did not make it too tight. There is some play. Hope this clarifys. If not, send me an email.