Mitutoyo’s M Plan APO objectives are well-known in the macro photography world for setting the standard of excellence for long working distance and optical performance. How did Mitutoyo achieve this kind of performance? They designed the objectives larger and longer with a 95mm parfocal length avoiding outdated and restrictive designs used by the competition. Mitutoyo makes a wide range of different objectives for different applications and wavelengths of light, UV, NUV, Visible & NIR, but the two most popular types for photography are the M Plan APO, metallurgical plan apochromatic, and BD Plan APO, Bright/Dark Field plan apochromatic. The BD Plan APO and M Plan APO versions have identical optical designs.
Why the Mitutoyo Plan APO?
The strengths of the M Plan and BD Plan APOs are the chromatic correction, large image circle, and long working distance from 5x to 100x. The low to mid range prices on the used market makes them popular with photographers. In addition to being infinity corrected, these objectives are completely corrected so they do not need any tube lens correction.
The Mitutoyos M Plans and BD Plans are my favorite lines of objectives, I own the range from 5x to 100x and I use both BD and M Plan versions.
MITUTOYO M PLAN APO 5X 0.14 OBJECTIVE SPECIFICATIONS
Mitutoyo Part Number: BD Plan Apo 5x : 378-832-4, M Plan Apo 5x : 378-802-2
Official name: M Plan Apo 5X/0.14 Long working distance objective
Objective type: Industrial inspection systems
NA and Nominal Aperture: This lens has a numerical aperture of 0.14, this is a nominal aperture is f/2.98 and an effective aperture of f/17.86.
Focal length: 40mm
Parfocal length: 95mm (Nikon objectives are designed with 65mm and 75mm, Qioptiq uses a 125mm parfocal length)
Working Distance: 34mm
Long Working Distance: with 34mm of working distance you will have enough room to set up lighting without much hassle.
APO Correction: An apochromatic or APO objective is corrected for chromatic aberration at the red, blue, and yellow wavelengths. This really adds to the subjective perception of sharpness. An APO objective should have correction of both types of chromatic aberrations or CAs, lateral CAs, or color fringing, and longitudinal CAs, or LoCAs, also called Bokeh CAs.
Resolution: the resolving power of this objective is rated at 2 µm (micron) which gives you a value of 10µm on the sensor so should make it a good choice for sensors in the 4-5 µm (micron) range like the Nikon D810 at 4.88 µm pixel size. The Mitutoyo Plan APO 2X, 5X, 10X all give a constant value of 10µm in the sensor multiplying the resolution with the magnification factor.
Image Quality: the Mitutoyo 5X has the IQ that these objectives are known for, sharp and without CAs (chromatic aberration). The IQ of these lenses are usually used as a reference for a lot of macro photographers.
Mounting Threads: M26 x 36TPI or M26 x 0.706mm
Coverage: Mitutoyo quotes a 30mm diameter image circle. This lens will cover a full frame DSLR sensor, but the corner performance is much better with a cropped frame or APS-C sensor body.
Infinity-corrected: to use a Mitutoyo Plan APO infinity corrected objective for photography, a secondary 200mm (or tube) lens is required for installation.
For a microscope objective, the Mitutoyo Plan APOs are massive, but they were designed this way for a reason. When Mitutoyo set out to design these lenses they wanted the best combination of working distance and optical performance so they went with a new approach by making the objectives larger and longer with a longer parfocal length, this brought the designs goals within reach.
M Plan Image Example at 5x
Resized to 1500 pixels
Mitutoyo M Plan 5X APO Plan with Sigma LSA tube lens and Sony A6300 body.
100% crop at 5x
100% center crop Mitutoyo M Plan 5X APO Plan with Sigma LSA tube lens and Sony A6300 body.
100% corner crop at 5x
100% far rigth corner crop Mitutoyo M Plan 5X APO Plan with Sigma LSA tube lens and Sony A6300 body.
SETTING UP THE M PLAN APO FOR PHOTOGRAPHY
Objectives designed to be used with darkfield illumination, like the BD Plan APOs, have a special lighting design consisting of a 360-degree hollow chamber surrounding the centrally located lens elements. To use BD type objectives for photography you have to block that circular chamber. I blocked this light channel the easiest way possible by using a disk made from ProStar flocking material using a disk cutter that I bought at my local $1.50 store.
THE COMPETITION
There are a few good Nikon 5X objects, like the LU Plan Fuor 5X 0.15, that might out resolve this lens in the center but the Mitutoyo has a much larger and more useful image circle. So unless you are shooting with a small format camera, the Mitutoyo is a better choice.
There is an objective with better resolution and good coverage, the Mag.x LD Plan APO 5X 0.20, but the working distance is shorter, at 18m vs 34mm for the Mitutoyo. A detailed review of the Mag.x 5x is available here: https://www.closeuphotography.com/qioptiq-magx-5x-objective/ on this site.
Qioptiq Mag.x LD Plan APO 5x / 0.20 Objective and Mitutoyo M Plan Apo 5X 0.14 objective with the Nikon Plan Apochromat 4x finite objective for scale.
Mitutoyo M Plan APO 5x/0.14 Objective unboxed
The Bottom Line
I can easily recommend this objective, for photography, but before you buy one, be sure to take a look at the warning below about buying used objectives. You really can't go wrong with any of the Mitutoyo M Plans and the 5x M Plan APO is one of the best in the series for photography, and one of my favorites.
Unlike a lot of high-performance objectives, see the test of the Nikon Plan APO 4x here: https://www.closeuphotography.com/4x-test-part-two-high-end-objectives, the Mitutoyo M Plan APO series really works well for photography.
5x M Plan APO Ratings
What I Like
-Large image circle for good coverage
-Consistent performance over the entire image circle
-Designed to be used without a cover-slip
-Flat field
-Long working distance
-Low to mid-range prices on the used market
-Easy to find on the used market
-Designed with all chromatic correction in the objective
What I Do Not Like
The polished chrome body, I prefer the matte finish of the BD Plan APO objectives.
PRICE AND AVAILABILITY
The Mitutoyo M Plans and BD Plans are all Plano Apochromats and this level of correction is typically very expensive, but thanks to the high volume production, Mitutoyo is able to keep the cost down. These objectives are widely used in manufacturing and research around the world so there is always good stock on the used market which keeps the prices reasonable.
Prices on the secondary markets are excellent, used prices in 2017-2018 are from $250 and up for a BD Plan APO 5x in decent shape, with an average starting around $400. In January 2018 I bought a brand new, unopened, in-the-box M Plan 5x, for only $400. There are super deals out there so don't pay too much. M Plan APOS are slightly more than the BD Plan versions, both have identical optical designs.
You will come across SL Mitutoyo objectives on the used market but these have a lower NAs than the normal M Plan and BD Plans so I would avoid them. There are also HR (high resolution) versions from Mitutoyo but they are very expensive, about 6 times the price of the standard units.
Objectives damage easily, one drop can cause performance issues so the best place to buy a Mitutoyo is from an online store in the US with return privileges, just watch for re-stock fees. If you try Ebay make sure that you only buy from a seller that offers returns with good feedback and is from the US.
In the last year Ebay has been flooded with re-sellers from China that are all placing Ebay ads with the very same objectives without physically owning the objectives and marking the prices up 100%. Buying from China is a huge risk, its not worth it, believe me, after 2 bad experiences, I won't risk buying from China again. On the other hand I have had nothing but very good experiences buying from South Korea and Japan. If there was an international contest for excellence in packing lenses, South Korea gets the gold medal. Chinese sellers use old bubble wrap and used boxes and do not give any consideration to the fact that they are shipping fragile items.
LINKS FOR MORE INFO:
Edmunds Optics: https://www.edmundoptics.com/microscopy/infinity-corrected-objectives/Mitutoyo-Infinity-Corrected-Long-Working-Distance-Objectives/
Mitutoyo Objective catalog: http://www.mitutoyo.co.jp/eng/support/service/catalog/04/E14020.pdf
Mitutoyo microscope catalog: http://www.mitutoyo.com/wp-content/uploads/2016/09/I-section-Microscopes.pdf
Microscope Objective Specifications
Identification of the properties of an objectives is easy because most parameters are inscribed or printed on the outer housing (or barrel) of the objective.
Image source: https://www.thorlabs.com/images/tabimages/Objective_Identification_D3-780.gif
Mitutoyo M Plan APO 5x/0.14 objective dimensions