Another good one: Reichert 6.5x 0.15

morfa · Post by **morfa** » Sat Sep 18, 2010 8:21 am

This is a rather humble looking little objective that I find myself using a lot:

It's designed for a tube length of 250mm where it provides roughly 6.5x magnification with a NA of 0.15. On an APS-C sensor it seems to perform well at 4.5X too.

Considering the tube length and the brand I'm guessing it's intended for use on Reichert's MEF2 metallurgical microscope. But I'm not really sure and if anybody knows something – please let me know!

From what I've seen so far it's pretty much completely CA free (like the JML) and the NA is not to shabby considering the magnification. Furthermore the barrel is very unobtrusive from a lighting standpoint and the WD is a comfortable 25mm.

I used this with my recently posted stacks of a Frit fly: http://www.photomacrography.net/forum/v ... hp?t=10911

I used it at 4.5x here (horizontally shifted 2.5° in ZS, but still holding up fairly well): http://www.flickr.com/photos/johnhallme ... 592459772/

Barry · Post by **Barry** » Sat Sep 18, 2010 8:30 am

If you go to 4,5x does the NA still count as 0.15?
(sorry, am not familiar with microscope objectives....)
The images look very, very clean.

Barry

rjlittlefield · Post by **rjlittlefield** » Sat Sep 18, 2010 8:58 am

Barry wrote:If you go to 4,5x does the NA still count as 0.15?

No, the NA will be slightly smaller at lower magnification. This is because NA describes the angle of the cone of light that is accepted by the lens. To focus at lower magnification, you have to move the lens farther from the subject. Of course the aperture is fixed width, so increasing the distance makes the cone narrower, thus smaller NA. But the change is not large, only to about NA 0.14 instead of 0.15.

--Rik

morfa · Post by **morfa** » Sat Sep 18, 2010 9:37 am

I was actually very close to asking the same question Barry did but incorrectly managed to convince myself the answer was "yes".

Thank you Rik!

morfa · Post by **morfa** » Sat Sep 18, 2010 10:15 am

Perhaps I should add this:

My experiences with the 6.5x 0.15 lead me to believe this one could be worth trying:

But nope, I was surprised to find it utterly useless for "our" purposes – very small image circle and the working distance completely disappears as the extension approaches 250mm. At 250mm the focal plane seems to be flush with the front face of the front element (dust particles stuck to the front element appears perfectly sharp) and the corners of the frame are still black. This seems very strange to me – does anybody have an explanation?

Barry · Post by **Barry** » Sat Sep 18, 2010 10:42 am

Thanks for clearing the NA issue, Rik.
But, still, the effective aperture of a microscope objective when decreasing the magnification is better than compared with a macro/enlarger lens.....correct?

0.14 or 0.15 - the images taken with this lens look very good. Nice find, John!

Pau · Post by **Pau** » Sat Sep 18, 2010 10:49 am

May it be possible that it did lost its front lens? (Beacuse it's clearely stated 250/- this behavoir is totally absurd.

In other hand, its NA is small for a 4X lens (0.08 is typical for 2x or 2.5X objectives), so it don't seem too intersting.

morfa · Post by **morfa** » Sat Sep 18, 2010 11:24 am

May it be possible that it did lost its front lens?

Yes, perhaps you're right! I find it hard to tell just from looking at it but the front face does look more convex than I'm used to seeing in objectives so right now I'm leaning towards your explanation as well.

Is something missing here?

In other hand, its NA is small for a 4X lens (0.08 is typical for 2x or 2.5X objectives), so it don't seem too intersting.

Well.... If it were like the 6.5X it would've been good already at 170mm and then it would have behaved more like a 2.7X. Even if the NA isn't too good I often find it convenient to have a set of similarly shaped lenses to be able to take a series of shots (typically: full body - portrait - detail) at different magnifications without having to rearrange the lighting too much.

g4lab · Post by **g4lab** » Sat Sep 18, 2010 12:13 pm

C. Reichert of Vienna was much less well known than Leitz, Zeiss, or Wild.
But everything I saw of theirs, was absolutely first rate. They had a number of innovative products.

Therefore, I am not surprised that one of their objectives should turn in a stellar performance.

They were phagocytized in the corporate consolidations of the 1980s.

John, your pictures continue to be wonderful.

Gene

rjlittlefield · Post by **rjlittlefield** » Sat Sep 18, 2010 12:32 pm

Barry wrote:But, still, the effective aperture of a microscope objective when decreasing the magnification is better than compared with a macro/enlarger lens.....correct?

Yes, usually, but this is a subtle issue.

To deliver NA 0.14 at 4.5X magnification, an ordinary lens would have to be about f/2.9. (Under reasonable assumptions the formula is f-number = 1/(2*NA) * m/(m+1) .)

So it would seem on the surface that an f/2.8 enlarger lens would work just as well.

The catch is that enlarger lenses are not designed to run best wide open -- an f/2.8 enlarger lens probably delivers its sharpest image at f/4 or perhaps even smaller.

But the microscope objective is designed to give its sharpest image wide open.

As a result, the fair comparison is between the NA 0.14 objective and the enlarger lens at f/4, and then it's clear that the objective has a significant advantage.

If you get a high quality macro lens that is designed to run best wide open at f/2.8 or wider, than it will behave very much like the microscope objective at NA 0.14.

--Rik

Perl · Post by **Perl** » Sun Sep 19, 2010 12:16 am

Hi John !

Have some Reichert Manuals in PDF format that i can send you if you like

Regards
Pär

morfa · Post by **morfa** » Sun Sep 19, 2010 2:47 am

Thanks for the kind offer Pär!

I found a large number (>60) of old Reichert manuals and brochures here: http://www.science-info.net/docs/reichert/

If you have manuals from a different source I'd love it if you could send them to me!

I vaguely recall reading somewhere that "np" stands for something similar to "DIC". I quickly scanned through the pdf's trying to confirm this but I couldn't seem to find it again.

Perl · Post by **Perl** » Sun Sep 19, 2010 3:54 am

Hi John !

Just mailed you the List

The Site You Pointed Out - I Guess have the same Manuals more or less , They Came from me in begining

Regards
Pär

Barry · Post by **Barry** » Sun Sep 19, 2010 8:07 am

Thus this Reichert lens is f2.9 and at its optimum....good thing!
Which enlarger/macro lenses are best wide open? I found them all best stopped down with 1 (macro lenses, some enlarger lenses) or 2 (most enlarger lenses) stops.

The componons and apo-componons are regularly seen in fixed aperture execution, and notably at the maximum of their variable aperture executions (28/4, 40/2.8, 45/4) > would this mean they are at their optimal designed apertures? (Or is this wishful thinking...?)

Get those Reicherts in production again.

Barry

ChrisLilley · Post by **ChrisLilley** » Sun Sep 19, 2010 9:09 am

What is the com[licated-looking square-ish bit or metal with a thumbscrew and three done-headed screws for? Is that how it attaches to the microscope? Does the objective itself use an RMS mount, or something else?