I discovered I had stashed Wayne's June 9, 2007 post on this subject
which mentions the same 46.5mm dimension and includes a link to the
finished product. Maybe he forgot he had it. Also of importance is the
note about lack of vignetting - Chuck Norcutt
------------------------------------------------------
A few weeks ago there was some discussion about the Olympus hood/filter
adapter for the OM Zuiko 18mm f3.5. I volunteered to bore out a
49-->72mm step-up ring to see if it could be used as a substitute
hood/filter adapter. I obtained a cheap (about $US7) step-up ring from
www.camerafilters.com and bored the inside of the 49mm threaded section
on the lathe from 45.2mm to 46.5mm (same ID as the Oly hood) which
fitted perfectly on the 18/3.5 even though the threaded section was
0.5mm longer than the Oly version. As the step-up ring is flat the
front element of the 18/3.5 still projects about 1.5 mm from the front
of the ring so I added a filter ring from which I had removed the glass.
As the filter was a fairly thick the resultant hood is about 2mm
deeper than the Oly hood but allowed me to mount a thin Hoya on top of
the combination without getting any vignetting.
This link takes you to a page which shows a few images of the step-up
ring mounted on the 18/3.5:
<http://lrh.structuregraphs.com/test/hood.htm >
The bottom line is that it seems a substitute hood can be made fairly
easily if you can't find/afford the original Oly.
..Wayne
--------------------------------------------------------
Piers Hemy wrote:
> The overall depth from front edge to back is 10mm
> The 49mm thread is 2mm deep.
> The 72mm thread is 3.4mm deep
> The inside diameter of the 49mm threaded portion is 46.5mm
> The critical dimension is the last one - you can find 49mm step up rings
> which have walls thin enough to fit the gap between the lens 49mm thread and
> the front element, but you will have to look hard.
>
> Good luck!
>
> Piers
>
>
> -----Original Message-----
> From: Olaf Iwert [mailto:oiwert@xxxxxxx]
> Sent: 07 August 2009 22:30
> To: olympus@xxxxxxxxxxxxxxxxx
> Subject: [OM] Step-up ring Zuiko 18mm lens OM System
>
> Dear all,
>
> Is there anyone out there who could supply me with a (brandnew) step up ring
> for an OM System Zuiko 18mm lens ?
>
> If noone has a hardware part, it would be very instructive to get a drawing
> of this part in order to verify how one could build one.....
>
> The second Iwert on the list
> --
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