Mitutoyo 2x NA 0.055, experience?

[nielsgeode]

Who has the Mitutoyo 2x NA 0.055 infinity corrected ELWD objective? How does it perform compared to the 5x NA 0.15 and 10x NA 0.28 objectives? Is it worth buying for increased image quality if you already have the MPE-65?

Thanx
Niels

[Chris S.]

Niels,

Here is a post I made a while back, reporting on the 2x/0.055 Mitutoyo M Plan Apo. The thread also includes a link to a report on this lens from Enrico Savazzi. The short answer is that the 2x Mitty differs from the 5x and 10x Mitty's primarily in exhibiting lateral (not axial) chromatic aberration, which I find to be easily correctable in Nikon Capture NX2.

Having no experience with the Canon MP-E 65, I can't compare these two optics. My own use of the Mitutoyo 2x emphasizes convenience. I typically shoot a subject at a range of magnifications, and prefer not to reconfigure my rig during a shoot if I can avoid doing so. If I'm shooting on the tube lens with Mitutoyo objectives, it's helpful to stay with Mitutoyo objectives between 2x and 100x. If shooting on the bellows, it's helpful to stay with finite objectives.

With a subject where top quality at 2x was specifically needed, I'd probably use a Printing Nikkor or Apo Rodagon on bellows.

But you are asking about--for 2x--popping off your MP-E 65 and swapping in a converging lens plus Mitutoyo 2x. Right? Purely conjecture, but I'd expect that the convenience penalty plus lateral CA of the Mitty 2x would make the MP-E 65 the better option. Also, from what I've seen (again, not having had the MP-E in hand), 2x is very much in the MP-E's strong zone.

Cheers,

--Chris

[Horstl]

....The short answer is that the 2x Mitty differs from the 5x and 10x Mitty's primarily in exhibiting lateral (not axial) chromatic aberration, which I find to be easily correctable in Nikon Capture NX2....

Chris,
the 2x is also very sensitive to variations in working distance.
If your equipment allows it, you should try to slightly increase w.d. - instead of the specified 34mm try something between 35 and 40. This doesn't completely eliminate CA at the borders, but I found it to give better overall perfomance.

with best regards,
Horst

[ChrisR]

Other Chris here..
Horst - do you mean by reducing the distance from "tube" lens to the sensor? What "tube" lens are you using?

[Chris S.]

Chris S here. . .

Horst, interesting idea. Like ChrisR, I take it that you have to change the distance between tube lens and camera in order to increase the working distance of the 2x lens?

If that's the case, it's probably not something I will do, as my integration of the tube lens was intended to give me something approximately as solid as a crow bar, and part of my approach to that involves keeping the relationship between camera and tube lens very firmly fixed. Still, it's useful information to have. (And something I might included in the next integration.) Thanks!

--Chris

[Horstl]

.. What "tube" lens are you using?..

Hi other Chris and Chris,

I observed this when playing around with an optical reducer that has been made for apochromatic refractors.
The 2x is different from the other Mitutoyos - it behaves very sensitive to any changes in the setup (distances/tube lens). Initially I thought it would be the most tolerable, because of it's lower nA and the relatively low effective aperture on sensor side, but it isn't.
It also didn't work well with the Oly BX Tube lens (180mm), very good in the center but CA's at the borders (other Mitutoyos work perfectly this way).
The best picture I got with the little Mitutoyo MT-4 Tube-lens/1x Adapter on FT-Sensors. But at eff. f/18 together with 16MP FT-Sensors diffraction becomes obvious. So, curious about what happens, I stuck it together with the optical reducer (in an improvised setup) and was surprised that I got wider field and better correction at the same time, but only when distance to the subject was large enough (specified 34mm as minimum).
Reducers for astronomical telescopes are often correctors (field flattener) at the same time. But the piece I used here (Optec NexGen 0,7x) is a "neutral" reducer - because the picture coming from the tube lens should already be well corrected. You can see a description and technical data here :http://www.optecinc.com/astronomy/catalog/17409.htm
I don't know exactly what's going on here, but assume that neither the picture behind the tube lens is perfectly corrected, nor the reducer is a "neutral" element. Luckily the reducer seems to mildly counteract the residual aberrations present in the intermediate picture.
This is a picture of the reducer+camera and another one showing how it is combined with the 2x objective and the MT-4 Tube lens.




Then the total field (approx. 15mm diameter on object side), and a comparison of CA's at the border (ca. 6mm from image center) with various objective-subject distances -(35mm/33mm/30mm; 100%view 16Mpix FT-camera, focus on center, no corrections, no stacking)

[ray_parkhurst]

I did my own tests to find the best performer around 2x from lenses at-hand. My results are here:

http://www.photomacrography.net/forum/v ... hp?t=20173

I found that the Canon MP35 was the overall winner. When I did the initial tests I did not have access to a Mitty 2x, but Peter De Smidt loaned me his to test. I ran it with a 180mm tube lens, so magnification was a bit different from the rest of the lenses, but IMO it was up there among the top 3-4 lenses tested. That said, from all I've read, the MPE65 should beat the MP35 at 2x, so it is probably going to be the winner vs the Mitty 2x. This is only conjecture as I've never tested a MPE65, but I've seen other tests that show it is sharper than the MP35...

[Craig Gerard]

Horstl,

Thank you for the detailed 'optical reducer' explanation and demonstration.


Craig

[Horstl]

....Like ChrisR, I take it that you have to change the distance between tube lens and camera in order to increase the working distance of the 2x lens?...

Sorry, I forgot to answer the question
Yes, you have to decrease the distance between sensor and tube lens to come into focus when w.d. to object is increased. With the setup shown above I could only slightly increase w.d. to 35mm, because it is optimised for the recommended distances (distance from sensor to reducer is fixed, that would be another critical point). Of course other parameters will also change slightly then - field size on object side does also increase.
I don't know where the optimum is and think it will also strongly depend on the tube lens that is used. But if somebody is trying this lens I recommend to experiment with distances - it can make a significant difference.

Horst