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  • RMS Thread Adapters

    RMS thread has an external diameter of 0.8", ca 20mm. There is a seller on Ebay offering "RMS to M42 adapters". They are for a more specialised RMS which is M25. It says that in the small print but RMS should mean RMS.

    I have just ordered a cone-shaped i.e. tapered, which will be much more usable than a disc.

    Harold
    The body is willing but the mind is weak.

  • #2
    Re: RMS Thread Adapters

    RMS is 0.8" 36 tpi, so no M25 isn't RMS, JIS might be the same even though I've seen it listed as 20.8mm.
    There are Nikon CF160 Infinite series objectives in 25mmx0.75 but they're the only microscope objectives I've found in 25mm there are at least 7 other threads used for quality microscope objectives! With Nikon alone using 27mm, 28mm & 32mm threads.


    I ordered the disc version which is actually MUCH more usable than the cone model. It's easy to add extension to the disc model, even with a helicoid so the distance can be adjusted. The ideal distance from the sensor for finite objectives is shown on the objective, most are 160mm but not all.
    You can also use the disc to mount an objective infront of a relay lens, which is needed for infinity type objectives.
    http://www.extreme-macro.co.uk/microscope-objectives/ gives lots of useful info on microscope objectives for photography.


    The cone type adapter probably has advantages in getting light to your subject with finite objectives. Maybe I should add one to my hoard of adapters, as not all subjects should be lit by transmission.
    Mike
    Compulsive photographic Dabbler.
    Flickr

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    • #3
      Re: RMS Thread Adapters

      Originally posted by Petrochemist View Post
      I ordered the disc version which is actually MUCH more usable than the cone model. It's easy to add extension to the disc model, even with a helicoid so the distance can be adjusted.
      I don't see your objections to a cone version. M42 tubes and helicoids will work just the same.

      I already have an RMS to filter thread adapter, should I venture into tube lenses.

      Harold
      The body is willing but the mind is weak.

      Comment


      • #4
        Re: RMS Thread Adapters

        Originally posted by Harold Gough View Post
        I don't see your objections to a cone version. M42 tubes and helicoids will work just the same.

        I already have an RMS to filter thread adapter, should I venture into tube lenses.

        Harold
        You can't reduce the length of the cone (infinite objectives are easiest if close coupled to the lens)

        If you've already got an adapter to filter threads you've avoided the issue.


        I can use my disc model with a M42-52mm adapter on lenses or direct to helicoid/tubes without the relay lens. To date all my objectives are finite ones, but I've still tried them via a relay lens (not very useful as the working distance is only 1-2mm)


        The only other objection to the cone version is the cost ~5X the disc version, but if it aids lighting it's worth it!
        Last edited by Petrochemist; 20th March 2019, 05:14 PM.
        Mike
        Compulsive photographic Dabbler.
        Flickr

        Comment


        • #5
          Re: RMS Thread Adapters

          Originally posted by Petrochemist View Post
          You can't reduce the length of the cone

          If you've already got an adapter to filter threads you've avoided the issue.


          I can use my disc model with a M42-52mm adapter on lenses or direct to helicoid/tubes without the relay lens. To date all my objectives are finite ones, but I've still tried them via a relay lens (not very useful as the working distance is only 1-2mm)


          The only other objection to the cone version is the cost ~5X the disc version, but if it aids lighting it's worth it!
          Some of my lenses are extended up to 300mm! The Photar 25 is typically 100mm, so far.

          Harold
          The body is willing but the mind is weak.

          Comment


          • #6
            Re: RMS Thread Adapters

            Mounting the Photar 25mm for use on tubes.

            I thought I had posted this already but I had not. These have been rushed and could have been a bit more vertically framed! I used twin flash.

            The Photar 25mm is for high magnification macro (optimesed for about x 6.5?) and has a standard RMS thread. Although the whole world seems to know that the thread is for 20mm, some seller on Ebay sent me one for 25mm, so caution!

            The first image shows a conical 20mm RMS to M42 adapter. The M42 tubes are very cheap and useful for use on legacy macro lenses and helicoid versions are available. This conical version gives access at lose working distances where there is not spaced for a flush, standard type.

            The third image shows a 35mm film cassette tube, with some tape on the rim for a tight fit, used as a protective cap.

            The third image shows a couple of M42 tubes added to the extension and the fourth shows an M42 helicoid. The fifth shows the flush version on tubes (necessary for a shorter extension for lower magnifications).

            All of the above are attached to an M42 to m4/3 adapter. (The tripod mount is superfluous for my applications).

            For clarification, I have added an image of the adapter alone.

            The final image is from another session, showing a flush type on legacy Olympus OM tubes.

            Such an adapter may be suitable for suitable microscope objectives used for focus stacking. Some disagree *see earlier comments).

            Harold













            The body is willing but the mind is weak.

            Comment


            • #7
              Re: RMS Thread Adapters

              Originally posted by Petrochemist View Post
              RMS is 0.8" 36 tpi, so no M25 isn't RMS, JIS might be the same even though I've seen it listed as 20.8mm.
              There are Nikon CF160 Infinite series objectives in 25mmx0.75 but they're the only microscope objectives I've found in 25mm there are at least 7 other threads used for quality microscope objectives! With Nikon alone using 27mm, 28mm & 32mm threads.

              .

              I've seen JIS quoted as 20.2mm but also sources claiming its the same as RMS.


              I'd not found the 28mm thread for Nikon objectives, but it's used by some Reichert Microscope Objectives. Nikon also use a 26mmx0.75 thread for their BD210 finite objectives & measurement microscopes.
              Mitutoyo use a different pitch 26mm thread (36tpi) as well as a 40mm one.


              My own objectives add further to the mix as I have a c-mount model, and my microscopes use tiny 15mm 42tpi objectives...
              Mike
              Compulsive photographic Dabbler.
              Flickr

              Comment

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