Filters for Rapid-Omega 90mm

[Michel Hardy-Vallée]

The 90mm lens has a built-in Series VI thread, and I have confirmed this with a retaining ring.

However, it's also supposed to be removable, leaving behind a more standard 49mm thread.

Anyone can confirm this from experience? If so, what is the safest way to remove the Series VI thread without marring the lens?

 

[mwdake]

I removed mine a while back.
If I remember correctly it used a large rubber bung pressed against the series thread part which gave enough grip to twist out the series threaded part.

 

[Michel Hardy-Vallée]

I removed mine a while back.
If I remember correctly it used a large rubber bung pressed against the series thread part which gave enough grip to twist out the series threaded part.

So I tried just that today, but could not dislodge the series thread. I even used a small screwdriver to apply tangential force, and though the tip could bite into the metal of the series thread, it did not move.

Is there a set screw hidden somewhere that prevents the series ring to screw out?

 

[mwdake]

There is not a set screw.
I think they are in there pretty tight.
If you can’t get it removed you could maybe find a Series VI to 49, 52 or 55 adapter but make sure you get it the right way around.
I’ve heard Series VI is close enough to 44mm that it will work so a 44 to 49 adapter might work.

 

[Randy Stewart]

The various lenses for the KO take Series VI,VII, or VIII. The Series filter holder can be unthreaded on each lens, leaving a standard sized (by modern definition) filter thread. I do not know the current situation, but a couple of decades ago when I assembled my KO kit, the Series filters were being given away on ebay, so I bought up a full set of each Series size just for the KO. Even cheaper because I had a full Series VI set of filters left over from the later 1950s when I first got into photography. The idea of using threaded filters was then just being adopted, slowly because folks didn't want to buy filters to use on only one lens. Nikon made a big marketing leap back then by standardizing on the 52mm filter thread for nearly all of their lenses for the Nikon F mount.

 

[AgX]

Is there a set screw hidden somewhere that prevents the series ring to screw out?

In some cases on adapting rings I found them glued together. If the tinkerer did a good job (or bad, depends on perspective) you will not see a trace of glue...

 

[Michel Hardy-Vallée]

In the end, I bit the bullet and asked SK Grimes to make me adapters (Series 6 to 49mm, Series 7 to 52mm, and Series 8 to 67mm.

That way I can reuse my existing filters and don't need to fight the tight rings.

 

[mwdake]

Good solution.
Enjoy your Rapid Omega

 

[Michel Hardy-Vallée]

Well, for the record: I received today three filter adaptor rings from SK Grimes:

1) Series VI to 49mm
2) Series VII to 52mm
3) Series VIII to 67mm

All filters are nicely anodized, have very smooth fit, and thread easily. They allow the lens shades on the lenses to slide in and out without obstruction.

Now I can use standard-size filters on the Rapid-Omega, thus reusing the ones I already have for other cameras.

It's not a cheap solution, but it's clearly the best one.

 

[Chuck1]

just wondering a similar situation would be encountered with the koni 58mm (still looking for a shutter)

 

[Michel Hardy-Vallée]

The 58mm uses Series VII filters, so you're either going to need Series filters, an adapter, or you can try unscrewing the front thread of the lens and hopefully remove the Series ring (I never succeeded).

 

[ags2mikon]

The s-6 adapter is locked in with a set screw on the 90mm lens. I removed both of mine and installed them on the auto-up lenses. The 135mm and 180mm is s-8, but 67mm fits just fine. On the 58mm I used a s-7 to s-8 step up and 67mm filters thread into it just fine. On both 90mm lenses I installed a 49-67 step up ring and now just use 67mm filters. Some times tiffen series 8 adapters won't take 67mm filters but most Japanese adapters work well with 67mm.