Mitutoyo’s 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 They designed the objectives larger and longer with a 95mm parfocal length avoiding outdated and restrictive designs used by the competition.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.

MITUTOYO 5X BD 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: BD 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: M40 x 0.706 pitch (36 TPI) adapters can be easily purchased on Ebay so there are no problems to adapt this lens for photography.

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.

Important Note: The Mitutoyo BD Plan APO and M Plan APO objectives are not designed for biological lab use so they are meant to be used without a cover slip or cover glass.

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.

Mitutoyo BD Plan APO 5X and two Nikon Plan APO 4Xs, the Nikon Plan APO 4x/0.20 Infinity-corrected in the center and the Nikon Plan APO 4x/0.20 finite-corrected objectives on the right.

Mitutoyo BD Plan APO 5X next to the two Nikon Plan APO 4Xs, the Nikon Plan APO 4x/0.20 Infinity-corrected and the Nikon Plan APO 4x/0.20  finite-corrected Objectives. — Mitutoyo BD Plan APO 5X next to the two Nikon Plan APO 4Xs, the Nikon Plan APO 4x/0.20 Infinity-corrected and the Nikon Plan APO 4x/0.20 finite-corrected Objectives.

Setting up the BD 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.

Mitutoyo BD Plan APO 100x Objective with open BD light channel on the left, and a BD Plan APO 5x Objective with the BD light channel blocked on the right.

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.

The Mitutoyo M Plan APO 5x, Mitutoyo BD Plan APO 5x and the Qioptiq mag.x LD APO 5x.

PRICE AND AVAILABILITY

The Mitutoyo M Plans and BD Plans are all Plano Apochromats, but this level of correction is typically very expensive, but high volume production has made it possible for Mitutoyo to keep the cost down. Thankfully these objectives are widely used in manufacturing and research so there is always good stock on the used market keeping the prices down. 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 of around $400. I bought a brand new M Plan 5x, unopened and in the box, for $400 in January 2018 so there are super deals out there.

Objectives damage easily and there are lemons on Ebay, so the best place to buy a Mitutoyo is from an online store 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.

You will also see SL (super long working distance) versions on the used market but these will not perform as well as the M Plan or BD Plans since they have a lower NAs than the normal M Plan and BD Plans. There are also HR (high resolution) versions from Mitutoyo but they are very expensive, about 6 times the price of the standard units, $4750 vs $700 in the case of the 5x HR vs non-HR Plan APOs!

Installation of the Mitutoyo BD Plan for Photography

Installation of the Mitutoyo BD Plan 5x is very easy today thanks to the easy to find adapters on Ebay. The set-up below uses my M52 studio set-up and Sigma LSA tube lens, more information on both of these

is available here on Closeuphotography.com:

52mm Studio set-up: https://www.closeuphotography.com/52mm-setup

Sigma LSA tube lens: https://www.closeuphotography.com/sigma-life-size-attachment/

Mitutoyo BD Plan APO 5x and Sigma LSA tube lens with a Nikon D850.

Mitutoyo BD Plan APO 5x and Sigma LSA tube lens with a Nikon D850 side view.

Objective Dimensions

Mitutoyo BD Plan APO 10X objective with the outer case removed.

The outer cases on Mitutoyo BD objectives (and most Nikon BD objectives) can be unscrewed and removed. Shooting this way will you slightly better access to the subject for lighting.