Tube lens tests on D800E full frame

[rjlittlefield]

Recently I've been testing several tube lenses for use with full-frame cameras. This post is an initial report of what I've found.

Here's the setup.

Camera: Nikon D800E (36 megapixels full frame)
Shot as: JPEG fine, in-camera conversion which includes removal of lateral CA.
Target: black toner dots on white paper, from a copy machine.
Objective: Mitutoyo M Plan Apo 10X NA 0.28
Stacking: focus step 2 microns, Zerene Stacker DMap, Lanczos3 alignment interpolation
Post-processing: PS CS6, shift and crop, no sharpening, save for web.
Illumination: electronic flash (Canon 580 EX-II at 1/32 power through Opteka diffuser)

Tube lenses:
. Mitutoyo MT-1
. Thorlabs ITL200
. Raynox DCR-150, reversed, at reduced extension to match magnification of the other tube lenses
. Nikon MXA20696 (Edmund Optics #58-520)

The full-size output files can be found here:

Mitutoyo MT-1
Thorlabs ITL200
Nikon MXA20696 (Edmund Optics #58-520)
Raynox DCR-150

Here are representative crops from center, right edge, and upper right corner.

Center:


Edge:


Corner:


Elsewhere, I've recently commented that

The somewhat surprising result is that the images are very close to identical over most of the frame, but the Raynox is clearly superior in the very corners. This held true even after I shortened the Raynox bellows extension so as to match magnifications of the other two tube lenses.

I'll be testing more to see what happens with other objectives and with tweaks to the lens separations etc, but at the moment I would find it impossible to recommend anything as being superior to the Raynox for full-frame coverage.

The above images provide the basis for that comment.

It's mentioned above, but I think it's important to emphasize that these images have had lateral CA removed as an unavoidable side effect of shooting JPEG in the Nikon D800E. I had forgotten that it would do that until after I had already shot the series, but at this time I can't justify repeating the whole shoot so I'm posting them out as is. On the bright side, the removal works great. I ran a short test shooting raw+JPEG and processing the raws through Lightroom with no CA removal before stacking. The results from raw through Lightroom had much more lateral CA than I got from using the JPEGs, and in addition the detail rendering from the JPEGs was better too in that test.

I hope this is helpful.

--Rik

[Peter De Smidt]

Great test! Thank you for doing it.

[rjlittlefield]

I expect that somebody will ask about CA with the Raynox DCR-150.

Here's the data on that, four panels as follows (each at same focus and +- 30 microns):

1. Mitutoyo M Plan Apo 10X NA 0.28 objective with Mitutoyo MT-1 tube lens.
2. Mitutoyo M Plan Apo 10X NA 0.28 objective with Raynox DCR-150.
3. Nikon CFI BE 10X NA 0.25 (MRN70100) with Raynox DCR-150.
4. Nikon CFI60 10X NA 0.25 (MRL00102) with Raynox DCR-150.









I'll forego further comment for the moment, except to note that I've checked very carefully to be sure that the labels here match my contemporaneous notes about what frame numbers go with what lens setups.

--Rik

[liuto]

Very informative test! Thank you!
I'll just recently discovered the Sigma "Life-size attachment" 5+ achromatic diopter to be of similar quality as the Raynox. I tested both in unreversed position and there was only a slight degradation into the corners on a Nikon D610 FF camera with both tube lenses and a CFI60 4x lens. I still have to do a test with reversed tube lenses and I will present the results in a new thread.

Best regards
Hermann

[alligator]

Thanks for posting this. I am just making the jump from finite to infinite objectives and am still using a micro nikkor 200mm as my tube lens, but am interested in finding out about alternatives.

Aso: I am wondering If the CA removal is "automatic" when you use the D800E to shoot a JPEG file, or does it require some menu setting that I am unaware of?

[rjlittlefield]

I am wondering If the CA removal is "automatic" when you use the D800E to shoot a JPEG file, or does it require some menu setting that I am unaware of?

According to Thom Hogan's Complete Guide to the Nikon D800/D800E,

There's nothing you have to do to enable chromatic aberration correction on the D800 models; it's done automatically when you shoot JPEG and TIFF images. If you use Capture NX2 for NEF conversion, it, too, can do lateral chromatic aberration, though in that program you can turn that correction on and off.

--Rik

[alligator]

According to Thom Hogan's Complete Guide to the Nikon D800/D800E,

There's nothing you have to do to enable chromatic aberration correction on the D800 models; it's done automatically when you shoot JPEG and TIFF images. If you use Capture NX2 for NEF conversion, it, too, can do lateral chromatic aberration, though in that program you can turn that correction on and off.

--Rik

Thanks! I did not know that.

[rjlittlefield]

I'll just recently discovered the Sigma "Life-size attachment" 5+ achromatic diopter to be of similar quality as the Raynox. I tested both in unreversed position and there was only a slight degradation into the corners on a Nikon D610 FF camera with both tube lenses and a CFI60 4x lens. I still have to do a test with reversed tube lenses and I will present the results in a new thread.

Excellent! I'll be very interested to see those results.

--Rik

[Fredlab]

Excellent.
Many thanks.

[Greenfields]

As usual, a very well researched and clearly presented report.

I have found that when used as a tube lens the "right" way round the performance of the Raynox DCR-150 with the Mitutoyo 5x, 10x, and 20x is just as exceptional but I have not compared the two orientaions so can't say if one is better. [The corner performance of the 20x on a full frame sensor is limited by CA with all of the tube lenses I have tried]

The performance of the Raynox is also remarkable because, according to the manufacturers, it is a triplet. Something we would dismiss as a taking lens because it would not have enough degrees of freedom to effectively correct aberrations. Of course, when used as a tube lens only the central portion of the Raynox would be used [a zone approximately equal to the exit pupil of the infinity objective if the objective was close] so I guess the lens would be diffraction-limited so its contribution to aberrations would be concealed by diffraction.

The most common design of Nikon's tube lens in their US patents for infinity objectives is a doublet pair:

"A typical infinity-corrected microscope employs a doublet pair as shown in Fig.13.3. The first doublet is plano convex. It provides three features: optical power, correction of spherical aberration, and correction of axial color. The second doublet is a meniscus lens with little optical power. It provides correction of coma and lateral color. The “bending” of the second lens from flat to curved corrects the coma of the first lens.
The doublet pair based on the Abbe number provides excellent correction of geometric aberration (Fig. 13.4). The performance on axis is diffraction limited at the d line. There is only axial color. At a 6.0-mm image field, there is no field curvature. However, the ray intercepts of the y plane indicate a significant lateral color for the g line (426 nm). The encircled-energy plot indicates nearly diffraction-limited performance at the d line at a 6.0-mm field height. A telecentric lens stop is essential to this design. The doublet pair is an effective solution for a CCD sensor with a 12-mm diagonal."

from Chapter 13 : Tube Elements in Optical Design of Microscopes by George H Steward, SPIE Press, 2010

Another advantage is that the entrance pupil of the Raynox can be placed close to and is much larger than the exit pupil of objectives so you do not get dark corners. With the Mitutoyo 5x lens, for example, the corners are conspicuously darker with the Nikon and Thorlabs tube lenses [I don't have the Mitutoyo] but not with the Raynox.

Henry

[rjlittlefield]

Henry, thank you for the additional information and the reference.

Is this the book you're talking about: http://www.amazon.com/dp/0819480959 ? (If so, I'm thinking to place an order immediately...)

--Rik

[Greenfields]

Yes, that is the book.

This is an example of the tube lens in Nikon's patents:



200mm Tube Lens from Nikon US Patent 7 889 432.

Nikon US Patents for infinity objective designs which are illustrated by this optical formulae for a 200mm tube lens span a decade:

5 889 618 5 982 559 6 128 139 6 519092
7 046 451 7 262 922 7 889 432


Henry

[edited to add Nikon tube lens data]

[rjlittlefield]

FWIW, Thorlabs gives a similar description for their ITL-200:

The lens features an apochromatic design consisting of two doublet lenses to correct lateral and axial chromatic aberration across the entire field of view in the visible range.

--Rik

[pierre]

Great !

Thanks Rik

[enricosavazzi]

" [...] A telecentric lens stop is essential to this design. "[...]

I don't understand this point. It cannot be a telecentric lens stop on the tube lens as a whole, because the tube lens is focused at infinity (i.e. the lens-sensor distance is equal to the focal length) and therefore any telecentric lens stop on the sensor side would need to be placed on the sensor plane. It cannot be a telecentric stop on the subject side because the microscope objective is placed less than one focal length from the tube lens.

Could it be that one of two doublets (perhaps the one closest to the microscope objective) has a telecentric stop? Would it be placed between the two doublets?