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Macro Getting really close

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Old 20th March 2019
Harold Gough Harold Gough is offline
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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
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Old 20th March 2019
Petrochemist Petrochemist is offline
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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.
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Old 20th March 2019
Harold Gough Harold Gough is offline
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Re: RMS Thread Adapters

Quote:
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
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Old 20th March 2019
Petrochemist Petrochemist is offline
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Re: RMS Thread Adapters

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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!
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Last edited by Petrochemist; 20th March 2019 at 05:14 PM.
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Old 20th March 2019
Harold Gough Harold Gough is offline
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Re: RMS Thread Adapters

Quote:
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
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