Olympus LM PLAN FI 20x/0.40 BD infnity corrected

Have questions about the equipment used for macro- or micro- photography? Post those questions in this forum.

Moderators: rjlittlefield, ChrisR, Chris S., Pau

anto74
Posts: 66
Joined: Thu Feb 06, 2020 11:48 am
Location: Italy
Contact:

Olympus LM PLAN FI 20x/0.40 BD infnity corrected

Post by anto74 »

Hello,
anyone can give me some information about this please?

Image

Thanks
Antonio

Chris S.
Site Admin
Posts: 4042
Joined: Sun Apr 05, 2009 9:55 pm
Location: Ohio, USA

Post by Chris S. »

From off-line communication, I understand that Antonio wants to know if this objective is suitable for use on a macro rig. For example, does it require CA compensating optics? What is its working distance?

--Chris S.

anto74
Posts: 66
Joined: Thu Feb 06, 2020 11:48 am
Location: Italy
Contact:

Post by anto74 »

Chris S. wrote:From off-line communication, I understand that Antonio wants to know if this objective is suitable for use on a macro rig. For example, does it require CA compensating optics? What is its working distance?

--Chris S.
Thanks Chris S. :)
I found this topic in another website: https://foromacrosmuymacros.com/viewtop ... f=12&t=858

Antonio

Ichthyophthirius
Posts: 1152
Joined: Thu Mar 07, 2013 5:24 am

Post by Ichthyophthirius »

Hi,

Have a look at the Industrial Component Guide, p. 17: https://www.olympusamerica.com/seg_indu ... _guide.pdf
Working distance is 12mm, thread is M26 x 36 TPI, FN is 26.5.

https://www.edmundoptics.eu/p/olympus-l ... ive/29238/

Olympus UIS/UIS2 objectives need no additional CA correction in the tube lens. You just have to find a suitable tube lens. Olympus tube lenses (U-TLU; single port tube with lens, p. 3) are regularly sold on Ebay.

Regards, Ichty

Chris S.
Site Admin
Posts: 4042
Joined: Sun Apr 05, 2009 9:55 pm
Location: Ohio, USA

Post by Chris S. »

Ichthyophthirius wrote:. . . need no additional CA correction in the tube lens. You just have to find a suitable tube lens.
Excellent!

Antonio, you already have a suitable tube lens, as I know you have an assembly based around the Raynox DCR 150, which we now know will work fine with this objective. Just be aware that this nominally 20x objective will deliver a bit over 23x magnification on your sensor when used with the Raynox.

(Why? Because the Olympus objective is designed to deliver 20x magnification with a 180mm focal length tube lens; your tube lens has a 208mm focal length; and magnification on sensor scales with focal length of tube lens. The math is: 208mm/180mm * 20x = magnification on sensor .)

Also be aware that you will need the proper adapter for your Raynox assembly. Since Ichty reports that the Olympus BD objective takes M26x36 TPI threads (the same as used by Mitutoyo objectives), you can look for either an Olympus BD adapter or Mitutoyo adapter that fits the front of your Raynox assembly. (TPI means "Threads Per Inch", or 0.706mm.)

Lastly, since this is a BD objective, there will be an outer ring that must be blocked to prevent light from leaking onto your sensor. This should be easy to do.

--Chris S.

Ichthyophthirius
Posts: 1152
Joined: Thu Mar 07, 2013 5:24 am

Post by Ichthyophthirius »

Yeah, also note that the distance between objective and tube lens is "50 mm to 170 mm" with the U-TLU tube lens. If the objective doesn't perform well with the Raynox initially, vary the distance between objective and Raynox to find the optimum configuration.

Regards, Ichty

anto74
Posts: 66
Joined: Thu Feb 06, 2020 11:48 am
Location: Italy
Contact:

Post by anto74 »

Thanks Ichty and Chris S. :)
Tomorrow morning i will go to get the objective :)
Antonio

anto74
Posts: 66
Joined: Thu Feb 06, 2020 11:48 am
Location: Italy
Contact:

Post by anto74 »

Hello,
I just bought the lens (120 euro). 50X was sold past days.
It looks in perfect condition, my friend detached it from his microscope. Now I have to figure out which adapter to buy for my kit with DCR150.
I hope upload test photos next days (if lens works!)
Antonio

anto74
Posts: 66
Joined: Thu Feb 06, 2020 11:48 am
Location: Italy
Contact:

Post by anto74 »

Hello Chris S., about this you said :
..there will be an outer ring that must be blocked to prevent light from leaking onto your sensor...
what does it mean "blocked"?
I must insert dark material to prevent light?
Thanks
Antonio
Chris S. wrote:
Ichthyophthirius wrote:. . . need no additional CA correction in the tube lens. You just have to find a suitable tube lens.
Excellent!

Antonio, you already have a suitable tube lens, as I know you have an assembly based around the Raynox DCR 150, which we now know will work fine with this objective. Just be aware that this nominally 20x objective will deliver a bit over 23x magnification on your sensor when used with the Raynox.

(Why? Because the Olympus objective is designed to deliver 20x magnification with a 180mm focal length tube lens; your tube lens has a 208mm focal length; and magnification on sensor scales with focal length of tube lens. The math is: 208mm/180mm * 20x = magnification on sensor .)

Also be aware that you will need the proper adapter for your Raynox assembly. Since Ichty reports that the Olympus BD objective takes M26x36 TPI threads (the same as used by Mitutoyo objectives), you can look for either an Olympus BD adapter or Mitutoyo adapter that fits the front of your Raynox assembly. (TPI means "Threads Per Inch", or 0.706mm.)

Lastly, since this is a BD objective, there will be an outer ring that must be blocked to prevent light from leaking onto your sensor. This should be easy to do.

--Chris S.

Chris S.
Site Admin
Posts: 4042
Joined: Sun Apr 05, 2009 9:55 pm
Location: Ohio, USA

Post by Chris S. »

anto74 wrote:Hello Chris S., about this you said :
..there will be an outer ring that must be blocked to prevent light from leaking onto your sensor...
what does it mean "blocked"?
I must insert dark material to prevent light?
Antonio,

Congratulations on acquiring what looks like a very nice lens at a favorable price.

In general, BD lenses (the letters stand for "Brightfield/Darkfield") have an outer barrel and an inner barrel. The inner barrel contains the glass elements of the lens. The outer barrel is hollow, and was intended to conduct light onto the subject (when used on a brightfield/darkfield microscope) from a light source on the microscope, shining through this outer barrel, onto the subject.

In your use, no such light source exists. And worse, this hollow outer barrel can permit light that bounces off the subject, or areas around the subject, to travel up this outer barrel and shine on your sensor. So yes, you must block this outer barrel to keep stray light from fogging your sensor.
I must insert dark material to prevent light?
That would be one way to do it, and I can think of other ways. This said, I've never had a BD objective in hand, so have not personally blocked this source of light leakage. But many other members of our forum have done this, and I would ask how they have done it.

Can folks who have experience in blocking off the outer barrel of a BD objective give Antonio practical advice?

--Chris S.

anto74
Posts: 66
Joined: Thu Feb 06, 2020 11:48 am
Location: Italy
Contact:

Post by anto74 »

Thanks again Chris S. :)

Now I'm testing the lens (only for testing I used insulating tape...) and I will post the shot.

Two questions:

1) I must block the light in outer ring near the subject or near the mount lens?

2) This objective has 180mm tube lens distance. I have variable kit lens purchased on Mjzkk website. I must calculate the tube length + Raynox DCR 150 length or I must consider only tubes length? 180m are only tubes or tube + DCR150?

Thanks,
Antonio

PS Sorry for my stupid question...but I'm learning...

Antal
Posts: 60
Joined: Fri Sep 28, 2012 4:29 am
Contact:

Post by Antal »

Ciao Antonio,

Basically you will set your tube lens focus at infinity. Therefor you focus with your tube lens (without any microscope lens! just the Raynox) on a very distant object.
Your raynox is now set at little more than 200mm. This will give you a little more than 20x mag with the olympus.
In a second step you just have to try out, make some testing reducing distance between sensor and TL. Some people have showed that some objectives work better with reduced distance sensor-TL..

Have fun with your lens!

Edit: Nominal focal length for the raynox seems to be 208mm
And: read mtf testing of the raynox here: https://www.photomacrography.net/forum/ ... hp?t=41049

ChrisR
Site Admin
Posts: 8668
Joined: Sat Mar 14, 2009 3:58 am
Location: Near London, UK

Post by ChrisR »

I have a couple of BD objectives with black rubber "O" rings blocking the light path (threaded end). Easy to use and work.
Chris R

anto74
Posts: 66
Joined: Thu Feb 06, 2020 11:48 am
Location: Italy
Contact:

Post by anto74 »

Thanks Antal and ChrisR :)
Antonio

Antal
Posts: 60
Joined: Fri Sep 28, 2012 4:29 am
Contact:

Post by Antal »

Haha, we want to see results!

Post Reply Previous topicNext topic