Lens Spotlight
Mitutoyo M Plan Apo 10x
The Mitutoyo M Plan Apo 10x was designed as a microscope objective for metallurgical analysis. In this field, as well as in focus stacking, it sets a benchmark against which other objectives must be measured.
The Objective
The Mitutoyo M Plan Apo 10x was originally developed for metallurgical applications. It is part of a modular objective series offering various magnification levels, all sharing a key feature: parfocality. All objectives in this series have the same mechanical length and working distance—except for the 1× model, which has a larger housing diameter.
The benefit of this standardized design becomes especially apparent when used with specialized microscopes, where the camera mount is calibrated once to fit the entire objective lineup—typically in combination with a fixed tube lens. However, parfocality also proves highly valuable in focus stacking setups: objectives can be swapped quickly and effortlessly without the need to modify or readjust the mechanical assembly.
The M Plan Apo 10x is optimized for reflected light use—unlike many traditional microscope objectives designed primarily for transmitted light in biological or medical contexts. This optimization improves color correction and contrast performance under reflected illumination, making the lens ideal for technical or material analysis tasks.
Another standout feature is its extended working distance, which is essential in metallurgical work—such as when side-angled light is needed for object illumination—but also offers significant advantages in macro imaging. In contrast to standard lab objectives, which often have short working distances due to their transmitted-light design, the long working distance of the Mitutoyo 10x allows for unrestricted and flexible lighting setups.
This makes the objective particularly well-suited for focus stacking photography with a full-frame camera. When paired with an appropriate tube lens, it can be seamlessly integrated into reproducible setups, where the generous working distance enables precise, shadow-free lighting and an unobstructed workspace—critical advantages when capturing delicate surface structures in high detail.
The Mitutoyo M Plan Apo 10x is part of a parfocal objective series with an identical housing diameter.
The Manufacturer
The manufacturer of this objective is the Japanese company Mitutoyo, a globally recognized leader in precision measuring and inspection equipment for industrial applications, particularly in metallurgy. These specialized objectives are available in Germany from distributors such as Edmund Optics (www.edmundoptics.de) or Novoflex (www.novoflex.de).
When introduced, this objective series set new standards by combining—for the first time—a long working distance with high numerical aperture (NA), excellent detail resolution, apochromatic color correction, and minimal distortion, even at the edge of an unusually large image circle of 30 mm for industrial optics. All objectives in this series are parfocal as well, significantly simplifying lens changes within a system. These performance characteristics were made possible by an unusually large lens diameter, which also resulted in unprecedented physical size and a noticeably heavier build.
While high-end metallurgical objectives already existed—such as Nikon’s “M Plan” series—the Mitutoyo lineup was the first to offer this combination of features. Other objectives that also perform well in focus stacking, such as Nikon’s “CF Plan Apo,” may achieve even higher NA values and therefore greater resolution. However, this often comes at the cost of a significantly reduced working distance or a smaller image circle, which can lead to noticeable image degradation at the edges—especially on full-frame sensors.
Furthermore, many of these older finite objectives do not require a tube lens—a feature appreciated by some users—but they often fall short in terms of usable image area and lighting flexibility compared to Mitutoyo optics. For users working with smaller sensors, these alternatives can still be very effective.
Ultimately, the decision to invest in the Mitutoyo series often comes down to conviction—and few who have worked extensively with these objectives for focus stacking ever feel inclined to return to other brands.
Given the high price of the original Mitutoyo optics, many imitations have emerged in recent years. These include the Japanese-made HLB objectives, which are also tested on this site, as well as various no-name optics that bear a striking external resemblance to the Mitutoyos—often at a fraction of the cost. However, one should not mistake external similarity for equivalent image performance: optics is a matter of precision engineering, and that quality is revealed not in the housing, but in the image itself.
Technical Specifications
Magnification: 10x
Numerical Aperture: 0.28
Infinity-corrected optics (requires tube lens)
Compatible tube lens focal length: 200 mm
Thread diameter and pitch: M26 x 36 TPI
Weight: 240 g
Body length: 61.0 mm
Body diameter: 30 mm
Parfocal distance (body length plus working distance): 95 mm
Exit pupil diameter: 11.2 mm
Focal length: 20.0 mm
Working distance: 34.0 mm
Resolution: 1.0 µm
Depth of field: 3.50 µm
Manufacturer’s recommended maximum sensor size: 2/3"
Imaging Performance – 208 mm Tube Lens
The following test images illustrate the imaging performance of the lens. The first shows an overview shot (full-frame sensor) taken with the Raynox DCR 150 tube lens, resulting in an approximate nominal magnification of about 10x. The two subsequent images each show an enlarged crop.
Test image at nominal magnification (DCR 150), with frame markers indicating the subsequent cropped enlargements – very good sharpness and no visible vignetting, free from chromatic aberrations, though with very slight pincushion distortion at the extreme edges.
The central cropped enlargement reveals very high detail sharpness without any chromatic aberrations. As expected, no distortions are present in the central portion of the image.
In the corner crop of the full-frame image, a slight decrease in detail sharpness is visible in the outer edge areas—particularly in the corners (seen here in the upper left)—as the 43 mm diagonal of the full-frame sensor slightly exceeds the image circle of the objective. Some minor chromatic aberrations are also noticeable here, but only within a narrow outer edge of the image. Smaller sensors are unlikely to capture any of these optical imperfections.
Center
In the center, the lens delivers outstanding image quality. Fine structures on the test pattern—such as closely spaced conductive traces, numbers, letters, and micro-grids—are rendered with razor-sharp precision and exceptional microcontrast. Lines appear crisp and well-defined, with no visible softening, and the differentiation between neighboring structural elements remains fully intact even at very close proximity. There are no color fringes, no noise in uniform areas, and no distracting blooming—classic indicators of apochromatic correction and the lens’s very high numerical aperture.
Extended Center
Image quality remains excellent throughout the extended central zone. Detail rendition is nearly on par with the central region. Transitions are clean, gray areas remain smooth, and lines stay sharp. Only under close inspection is there a barely noticeable drop in sharpness—still at a level far superior to that achievable with traditional macro lenses or zoom systems. The flatness of field is excellent, evidenced by the absence of field curvature or tangential blur. The overall image impression remains cohesive and well-balanced.
Edge Zone
In the edge zone, image quality begins to taper slightly—but in a gradual, well-controlled manner. Sharpness decreases subtly, and extremely fine details become just a touch less distinct than in the center. Nevertheless, all structures remain clearly visible, and contrast remains sufficient to keep key elements clearly recognizable. There are no significant aberrations—no coma, no noticeable chromatic fringing, and no geometric distortion—which is remarkable considering the lens’s specified image circle of 26.5 mm and its use on a 43 mm full-frame sensor. Vignetting is minimal and evenly distributed.
Overall Impression
In this test setup, the Mitutoyo M Plan Apo 10x proves itself to be a top-tier lens. Its strengths lie in its exceptionally high resolution, refined microcontrast, and well-balanced field correction. In both the center and extended center zones, it achieves near-perfect image quality. Even at the image edges, the quality remains impressively high, with minor compromises that are practically irrelevant in most center-focused macro photography scenarios.
What’s especially noteworthy is that this lens can be used on a full-frame sensor without significant degradation at the periphery—an uncommon trait for microscope objectives primarily designed for smaller sensor formats. For those needing the highest precision in compact imaging tasks—such as semiconductor documentation, materials inspection, or biological/technical structure analysis—the M Plan Apo 10x offers reference-level performance, provided it is used with the appropriate tube lens and on a stable, vibration-free setup.
Imaging Performance – 125 mm Tube Lens
The following test image is another overview shot, but this time taken with the Raynox DCR-250 tube lens, which reduces the magnification to approximately 6.25x instead of the nominal 10x. Some metallurgical microscope objectives from the aforementioned Mitutoyo series tolerate this setup, though not all to the same extent. This test is intended to show what kind of quality compromises can be expected with the Mitutoyo M Plan Apo 10x when used in this configuration.
Test image with DCR 250: The shorter focal length of this tube lens results in a lower magnification, and with this combination, loss of sharpness and distortion in the edges and corners become more pronounced. Additionally, the image area affected by these optical flaws is wider than in the DCR 150 image. However, chromatic aberrations are still only present in trace amounts and are barely noticeable.
In the central cropped enlargement, the level of detail is still very good, although the tiniest features appear slightly softer compared to the corresponding crop from the DCR 150 image. No chromatic aberrations are visible, and the image is largely free of distortion, although the corners of the crop already show a slight tendency toward pincushion distortion.
In the corner crop of the full-frame image, both distortion and blurring increase noticeably toward the image edge. This affected zone is wide enough to be potentially distracting when using a full-frame sensor. However, APS-C and MFT sensors are likely to capture these image flaws only in the very outermost corners, if at all.
Center
In the center, the image remains surprisingly good. Fine conductor paths and graphic structures are still rendered with considerable sharpness, and the lines are clearly separated. However, the edges no longer appear quite as precisely defined as in the specification-compliant configuration. Microcontrast has slightly diminished, and subtle gray-on-gray transitions exhibit a slight flattening of tonal values. The surfaces also appear somewhat less smooth, with a faint grain pattern beginning to emerge in some areas. This suggests the onset of spherical aberration—typical when corrective lens elements inside the system operate outside their intended positions.
Extended Center
In the extended center, the drop in image quality becomes more apparent. Structural separation weakens, microcontrast breaks down noticeably, and fine conductor paths visually converge. A slightly blurred impression begins to develop in places. Transitions between light and dark areas also lose clarity. The flatness of the optical field begins to shift: individual planes seem no longer perfectly projected onto the sensor—a sign of emerging field curvature or astigmatism caused by incorrect tube lens distance.
Edge Zone
In the edge zone, image quality drops off significantly. Lines lose definition, darker regions appear "smudgy," and highlights begin to bloom slightly. While individual structures remain visible, they look fuzzy and imprecise, giving the overall image a noticeably softer feel. Whereas the objective provides acceptable sharpness even at the edges with a 200 mm tube lens, this test reveals the limitations of using a significantly shorter projection distance. Early signs of vignetting and asymmetric light falloff are
Overall Impression
In this test setup with a 125 mm tube lens, the Mitutoyo M Plan Apo 10x operates well outside its optical sweet spot. While the central area still delivers usable results, noticeable image degradation begins already in the extended center—and the decline becomes clearly visible at the edges. This objective is optimized for maximum resolution and fine structural separation but can only achieve that performance when used with the precisely calculated tube lens focal length. If that focal length is significantly reduced, as in this case, the entire correction system is thrown off, generating errors that are especially apparent in such a high-performance lens..
Nonetheless, the image remains usable in the center and in some respects even surpasses lower-tier objectives operating under optimal conditions. For professional applications requiring maximum fidelity, however, operation outside of specifications is not recommended. Anyone seeking to harness the full potential of this exceptional 10x apochromatic lens—especially on a full-frame sensor—should adhere to the specified 200 mm tube lens. Only then can the impressive optical performance of this objective truly shine.
Imaging Performance – 208 mm Tube Lens: Microprocessor
This test image shows a highly magnified section of a microprocessor measuring 3 × 3 mm, captured using the Mitutoyo M Plan Apo 10x in its optimal configuration—with a 200 mm tube lens on a full-frame sensor. The image allows for an especially precise evaluation of the optical performance of this high-resolution apochromat (NA 0.28) in a realistic application scenario, demonstrating not only its sharpness and detail rendition but also its color accuracy.
Crisp, sharp details, good color contrast, no noticeable distortions in the corner areas, as the overview image was heavily cropped on all sides due to large white spaces on the left and right.
Center
In the center, the lens demonstrates impressive performance: fine structures, circuit traces, cell patterns, and memory-like arrays are rendered with exceptional clarity and sharpness. Especially notable is the excellent separation of closely spaced lines—even in highly condensed areas, individual structures remain distinctly discernible. The image impression is three-dimensional and almost analytical, yet free from harshness or overemphasis. Surfaces appear smooth and even, indicating superb correction of spherical aberration and residual astigmatism. No color fringing or chromatic shifts are visible, even in high-contrast transitions—a hallmark of a precisely apochromatically corrected optical system.
Extended Center
In the extended central zone, detail reproduction remains extraordinarily high. Even complex logic modules with dense line arrangements and low contrast gradients are rendered cleanly. Minor geometric deviations—commonly found near the periphery in other lenses—are not visible here. The sharpness plane appears impressively consistent across the entire usable image area, suggesting a minimally curved field projection. Contrast and tonal depth remain at a high level in this zone as well—there are no washed-out transitions or noticeable edge softness.
Edge Zone
In the outer image zone, the lens still performs remarkably well—especially considering use on a full-frame sensor with a 43 mm diagonal, while the manufacturer designed it for a significantly smaller image circle. While absolute resolving power diminishes slightly, lines remain clearly visible, transitions are still well-defined, and the overall image remains cohesive. No meaningful distortion, vignetting, or chromatic shifts are present. The loss in quality compared to the center is more academic than practical—it would hardly be noticeable in typical real-world applications.
Overall Impression
In this optimal configuration, the Mitutoyo M Plan Apo 10x proves itself a true high-performance lens. Its ability to render even the finest structures on a full-frame sensor with precision, contrast, and color fidelity makes it an outstanding choice for applications with the highest demands—such as semiconductor analysis, technical documentation, or scientific imaging of microstructures. The major advantage of this lens lies not only in its extreme central resolution but also in its striking uniformity across the entire image field. Even at the edges, its performance surpasses what many other optics can achieve in the center.
In practice, this lens is ideal for all scenarios where maximum structural differentiation in tight spaces is required. A stable setup, correctly matched tube lens, and precise alignment are essential—but when these conditions are met, this 10x apochromat delivers reference-level results.
Resolution Test
The Zeiss Resolution Test 300 allows the resolution of a microscope objective to be read as a numerical value. While this reading is somewhat subjective and not entirely exact (see details here), it still provides a useful general impression of the objective’s fine detail reproduction and resolving power.
The resolution value at the center of the lens, visible here in the two outer test fields, was read as 560 line pairs per millimeter (lp/mm) in the left field and 630 lp/mm in the right.
Conclusion
The Mitutoyo M Plan Apo 10x is a high-precision apochromatic objective known for its exceptional detail reproduction, standing out as virtually unrivaled in its price class. Across the central image field, it delivers impressive resolution, outstanding microcontrast, and remarkably clean separation of even the finest structures. Its high numerical aperture of 0.28 produces crisp, high-contrast images with minimal chromatic aberration — even when capturing the most challenging subjects.
While Mitutoyo does offer a high-resolution (HR) variant with a NA of 0.42, which further improves resolution and light-gathering ability, that version belongs to a significantly higher price tier — often up to ten times more expensive. This may technically justify its performance advantage, but for many applications, the economic tradeoff makes the standard 10x model the more pragmatic choice.
As with all objectives of this class, it’s important to note that the recommended image circle of 26.5–30 mm is technically exceeded when used with a full-frame sensor (43 mm diagonal). In practice, however, this has little consequence — assuming the objective is used with the specified 200 mm tube lens. In this optimal configuration, even the far corners of the full-frame sensor exhibit only minimal degradation in image quality, which is generally negligible for compositions with centrally placed subjects.
The situation changes with significantly shorter tube lens focal lengths — such as 150 mm or even 125 mm — for which this objective was not designed. In these cases, visible image aberrations appear in the peripheral zones, including a loss of sharpness, contrast, and flatness of field. While these limitations may be relevant in technical image analysis, they are of little consequence in most photographic use cases, especially classic macro photography where the subject lies near the image center.
It’s also worth noting that this objective was originally developed for very small sensor formats (up to 2/3"). On such sensors, it delivers uncompromising optical performance by utilizing only the well-corrected central portion of the lens. Even on APS-C or Micro Four Thirds formats, which stretch the image circle further, the quality remains well above average — with only minimal, barely noticeable losses toward the edges.
In conclusion, the Mitutoyo M Plan Apo 10x remains highly recommended for full-frame sensors — provided it is properly adapted and used with the correct tube lens. It offers outstanding image quality and optical precision, establishing itself as a benchmark for industrial, scientific, or documentary macro imaging. For anyone seeking maximum resolution alongside stable, color-accurate, and uniform rendering across the frame, this objective is a top-tier tool with a uniquely robust optical profile.
Advantages
Extremely long working distance, high image sharpness and detail accuracy, excellent color correction, parfocality within the objective series, allowing for easy lens changes.
Disadvantages
Unusual thread size requiring a special adapter (e.g., www.stonemaster-onlineshop.de); slight edge softness when used with a shorter tube lens focal length (DCR 250).
Daniel Knop, www.knop.de, www.danielknop.eu
Testbild mit DCR 250: Im Zentrum ist die Bildschärfe bei dieser Kombination nur moderat und deutlich geringer als bei der Nominalvergrößerung, und außerhalb des Bildzentrums lässt sie gewaltig nach. Hier zeigt sich auch eine leichte kissenförmige Verzerrung. Die Abdunklung des Rand- und Eckenbereichs ist deutlicher als bei Verwendung der DCR 150.
Das Bildzentrum hat noch gewisse Schärfe, aber feinste Details werden in Kombination mit der DCR 250 nicht mehr wiedergegeben.
Die Randzone weist starke kissenförmige Verzerrung und intolerable Unschärfe auf, die zur Ecke hin extrem wird (hier links oben). Im Vollformat ist diese Kombination aus Objektiv und Tubuslinse schlicht unbrauchbar.
Der direkte Vergleich mit dem Canon-Lupenobjektiv MP-E 65 mm bei Stellung 3,5x zeigt, dass das HLB Planapo 3,5x diesem sehr scharf abbildenden Makrospezialisten deutlich unterlegen ist. Das Canon bringt mehr Schärfe (Bild oben rechts), und der Schärfeabfall zum Bildrand und vor allem zu den Ecken hin ist beim Canon deutlich schwächer als beim HLB. Allerdings muss hier auch berücksichtigt werden, dass das HLB Planapo 3,5x neu weniger als die Hälfte dessen kostet, was für ein Canon MP-E 65 mm zu veranschlagen ist.
Vergleich HLB M Plan 3,5x – Canon MP-E 65 mm
HLB Planapo 3,5x (links) im Vergleich mit dem Canon MP-E 65 mm bei Stellung 3,5 (rechts), oben jeweils das rechte obere Viertel des Originalbilds, aufgenommen mit Vollformatsensor (Focus Stack), unten jeweils ein Sechzehntel des Originalbilds, entsprechend hochskaliert.
Fazit