JML 26mm f4.5 mounting solutions

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elf
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JML 26mm f4.5 mounting solutions

Post by elf »

Please post your mounting solutions here.

For initial testing, I just made a sleeve to fit the lens in my JML 21mm holder. This lens should be fairly easy to make an adaptor for since a standard size drill bit (20mm) can be used.

This is what I'm planning. It's sort of an inverse Lieberkühn reflector that will hopefully make it easier to get light to the front of the subject.

Image

AndrewC
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Post by AndrewC »

How exactly does that light the subject ?
rgds, Andrew

"Is that an accurate dictionary ? Charlie Eppes

elf
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Post by elf »

I should have said, it's almost a Lieberkühn reflector :)

The light source will be in the upper left with a barn door to block light hitting the lens.

rjlittlefield
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Post by rjlittlefield »

elf wrote:The light source will be in the upper left with a barn door to block light hitting the lens.
I have the impression that only the upper part of the reflector will be able to see the light source, while more than the lower half will be shadowed by the barndoor. Is this correct?

--Rik

lauriek
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Post by lauriek »

If the diagram is accurate it appears to me like the light will have to come in almost perpendicular to the lens to reflect onto the subject?

elf
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Post by elf »

rjlittlefield wrote: I have the impression that only the upper part of the reflector will be able to see the light source, while more than the lower half will be shadowed by the barndoor. Is this correct?

--Rik
Yes, but I expect to use mulitple flashes.
lauriek wrote:If the diagram is accurate it appears to me like the light will have to come in almost perpendicular to the lens to reflect onto the subject?
Yes, on further reflection (pun intended), I think a redesign is in order :)
This curved reflector doesn't offer any advantages over just a flat plate and actually looks like it would be more restrictive for where the flashes can be placed.

A real Lieberkühn reflector would be much better as it concentrates diffuse light at the focal point. I would need to use thicker stock to make one and also figure out how to machine it.

The primary requirement for this lens board is actually on the back side. I want to be able to use this at the minimum magnification. If I remove the recess at the rear of the lens, it will allow the lens to fit about 5mm into the mirrorbox on my camera (4/3rds mount) for an extension of 33mm (+ distance from the rear of the lens to the first principal plane). If my measurements are correct, there is actually closer to 8mm available between the mirror and the mounting flange. If they're wrong, I need a new camera anyway :)

AndrewC
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Post by AndrewC »

Having messed around with various reflectors, I'm of the considered opinion that you should just use a fairly open cone made out of a material offering a diffuse reflection (white paper ! ) and then just blast it with a lot of photons ! Change the position of the light source relative to the cone to get different effects - use snooted flashes or light pipes.
rgds, Andrew

"Is that an accurate dictionary ? Charlie Eppes

enricosavazzi
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Post by enricosavazzi »

My mounting solution, with the purpose of keeping things as simple and flexible as possible. The mount is a 12 mm long RMS extension (I bought a few off eBay some time ago). It was necessary to file off the thread of the female RMS mount with a Dremel multi tool and epoxy the lens into the mount. The lens barrel rests at the bottom of the mount, so alignment should not be a problem.

No time to test the lens yet.

eBay item n. 140411665857 is similar to the extension tube I used, although not identical.

Image
--ES

elf
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Post by elf »

My adaptor doesn't look much like the original drawing :) The step on the front is sized to fit a 28mm polarizing filter. The adaptor threads are 57mm X .75 to fit extension tubes and a lens board for my desktop setup. The back of the lens was cut off on a lathe

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Brodie Foster
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Post by Brodie Foster »

Last edited by Brodie Foster on Sat Dec 17, 2016 11:59 pm, edited 1 time in total.

Pau
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Post by Pau »

Take a look here:
http://www.photomacrography.net/forum/v ... sc&start=0
lots of ideas, but I don't kow if the barrel diameter of the 21mm and 26mm lenses is different
Pau

enricosavazzi
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Post by enricosavazzi »

Pau wrote:Take a look here:
http://www.photomacrography.net/forum/v ... sc&start=0
lots of ideas, but I don't kow if the barrel diameter of the 21mm and 26mm lenses is different
They are different: 20mm for the JML 26, 26mm for the JML 21.
--ES

Craig Gerard
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Post by Craig Gerard »

This item would make a suitable mount for the JML 26/4.5.

It would need some minor modification and some flocking or flare reduction paint. It mirrors Enrico's solution, outlined earlier in this thread.

I have a similar piece and will be using it for a JML 26/4.5 adapter.

http://cgi.ebay.com.au/ws/eBayISAPI.dll ... 0534582084

also

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0411665857



Craig
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

Brodie Foster
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Post by Brodie Foster »

Last edited by Brodie Foster on Sun Dec 18, 2016 12:01 am, edited 1 time in total.

Craig Gerard
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Post by Craig Gerard »

Brodie,

I also purchased one of those rafcamera items. It arrived yesterday. I intend to use it on its own. Having a closer look at it now....

The 12mm refers to the internal depth of the piece. It was designed to be used for another purpose. For our purposes it is suitable. The internal and external threads (male and female) are RMS.

There is something happening with the rafcamera threads; but it does attach securely to an RMS adapter. I tried it with a few different adapter rings and all were okay.

Once the internal threads are carefully filed down on the inside of the rafcamera piece, the JML 26/4.5 should fit well. There is an internal ridge which will serve well as a 'seat' as Enrico mentioned.

I'm initially intending to use a friction fit, until we determine whether this lens works better reverse mounted.

The other brass adapter is of similar specifications and was mentioned as a possible alternative.



Craig
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

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