Lens Spotlight
Mitutoyo M Plan Apo 5x
The Mitutoyo M Plan Apo 5x was designed as a microscope objective for metallurgical applications. In this field—as well as in focus stacking—it sets the standard by which other objectives must be measured.
The Objective
The Mitutoyo M Plan Apo 5x is a lens designed specifically for metallurgical applications. It is part of a series of objectives with different magnification ratios, all of which are parfocal—meaning they share the same overall housing length and working distance. The housing diameter and thread are also identical throughout the series, with the exception of the 1x objective, which has a slightly different diameter.
This parfocality is particularly advantageous when used on specialized microscopes, where a fixed-length camera extension—often with an integrated tube lens—is mechanically aligned for all objectives in the series. However, it is also highly beneficial for focus stacking setups, as it allows for seamless switching between objectives in the series without requiring additional adjustments.
The Mitutoyo M Plan Apo 5x was optically corrected for use with reflected light, which can result in superior color fidelity compared to some microscope objectives primarily designed for transmitted light applications.
A long working distance is essential for many metallurgical tasks, especially because the illumination typically comes in from the side. This is a major difference from most microscope objectives developed for laboratory use (in fields like medicine, biology, and so on), where transmitted light is standard and a long working distance is often unnecessary—or even problematic.
While the Mitutoyo M Plan Apo 5x was originally intended for use with dedicated microscopes, its long working distance makes it exceptionally well suited for focus stacking applications. When paired with the appropriate tube lens, it can be mounted on a full-frame camera. The generous working distance makes lighting the subject significantly easier.
The Mitutoyo M Plan Apo 5x is part of a parfocal objective series with an identical housing diameter.
Der Manufacturer
The manufacturer is the Japanese company Mitutoyo, which—alongside these specialized objectives—produces a wide range of testing and measurement equipment for metallurgical applications. In Germany, these objectives are available from companies such as Edmund (www.edmundoptics.de) or Novoflex (www.novoflex.de).
When first introduced, this objective series set new standards by offering a unique combination of long working distance, high numerical aperture (NA)—and thus high resolving power—as well as excellent color correction and virtually distortion-free imaging all the way to the edge of its comparatively large 30 mm image circle. Additionally, as mentioned, all objectives in the series are parfocal. This was made possible only by the extraordinarily large lens diameters, which pushed the size and weight of these objectives to previously unseen levels.
There had been excellent metallurgical objectives before—such as Nikon’s “M Plan” optics—but the Mitutoyo line introduced this particular set of features in a new and compelling configuration. Other objectives that are also suitable for focus stacking, such as Nikon’s “CF Planapo,” sometimes offer even higher NA values and therefore better resolution than the Mitutoyos—but typically at a cost: reduced working distance or (often!) a smaller image circle, which can lead to edge aberrations when used with full-frame sensors. On the other hand, most of these older finite objectives don’t require a tube lens, which many users appreciate—and those working with smaller sensors are likely to be well served by them. Choosing the Mitutoyo objective series ultimately comes down to personal conviction—but among those who’ve used them extensively for focus stacking, few ever switch to another brand.
However, since Mitutoyos are quite expensive, many copycat models have emerged on the market. These include HLB objectives, also made in Japan and featured in this comparative test, as well as numerous no-name optics that bear a striking resemblance to the “Mitus,” usually sold at significantly lower prices. That said, visual similarity alone should not be taken as an indication of comparable image quality.
Technical specifications
Magnification: 5x
Numerical Aperture: 0.14
Infinity-corrected optics (requires tube lens)
Compatible Tube Lens Focal Length: 200 mm
Thread Diameter and Pitch: M26 x 36 TPI
Weight: 230 g
Housing Length: 61.0 mm
Housing Diameter: 30 mm
Parfocal Distance (Housing Length + Working Distance): 95 mm
Exit Pupil Diameter: 11.2 mm
Focal Length: 40.0 mm
Working Distance: 34.0 mm
Resolution: 2.0 µm
Depth of Field: 14.00 µm
Imaging Performance – 208 mm Tube Lens
The following test images illustrate the imaging performance of the objective. The first shows an overview shot (full-frame sensor) taken with the Raynox DCR-150 tube lens, resulting in an approximate nominal magnification of 5x. The two subsequent images each show a magnified crop of that image.
Test image at nominal magnification (DCR 150), with frame markers for the cropped close-ups that follow – excellent sharpness, no visible vignetting, free of chromatic aberrations, though with slight pincushion distortion at the extreme edges.
The central cropped close-up shows, as expected, excellent detail sharpness with no chromatic aberrations.
In the corner crop of the full-frame image, a slight decrease in detail sharpness can be seen at the outer edge (here in the upper left). The 43 mm diagonal of the full-frame sensor slightly exceeds the image circle of the objective. However, this remains fairly moderate, as do the faint traces of chromatic aberration at the extreme periphery.
Center
The central structure is remarkably clear and finely rendered. Lines remain consistently sharp, even in the densely packed areas of the test target. There is no visible spherical aberration or color fringing. Edge contrast is high, and fine detail is well differentiated. This reflects excellent centering and a well-corrected optical design, especially considering the narrow aperture at NA 0.14.
Extended Center
Detail reproduction remains very good in the mid-zone. Line structures are still clearly resolved, though there is a slight loss of microcontrast. Upon closer inspection, one can detect early signs of minimal field curvature or a slight deviation from flatness—typical for infinity-corrected objectives used on flat sensor planes. The structures are still clearly distinguishable, indicating very even illumination and effective correction of astigmatism.
Edge Zone
The most noticeable drop in quality occurs in the extreme image corners—though even here, it remains moderate for the Mitutoyo M Plan Apo 5x. The fine circuit patterns appear slightly softened, with the beginning of detail loss in the most densely packed segments. Some lines start to merge slightly, suggesting mild coma or field curvature. Color fringing is barely present—an indication of the apochromatic correction. Overall, edge performance remains usable, though not at the same level as the center.
Overall Impression
In this configuration, the Mitutoyo M Plan Apo 5x delivers excellent central resolution with only minor degradation toward the edges. For full-frame, sensor-filling macro photography, it is outstanding in its class—particularly when paired with careful focus stacking. The slight field curvature and moderate edge falloff are typical of telecentric objectives used on flat sensors and should not be seen as drawbacks, but rather as indicators of the need for precise extension adjustment and, if necessary, stack compensation in the edge zones.
Imaging Performance – 125 mm Tube Lens
The following test image is another overview shot, this time taken with the Raynox DCR-250 tube lens, which reduces the magnification to approximately 3.125x (instead of 5x). Some metallurgical microscope objectives from the aforementioned Mitutoyo series tolerate this approach reasonably well—though not all to the same extent—and this test aims to reveal what qualitative compromises can be expected when using the Mitutoyo M Plan Apo 5x under these conditions.
Test image with DCR 250: The shorter tube lens focal length results in a lower magnification, and with this combination, vignetting is visible around the edges—especially in the corners.
In the central cropped close-up, detail sharpness is consistent and still quite good. No chromatic aberrations are present, and the image is free of distortion.
In the corner crop of the full-frame image, both distortion and blurring increase noticeably toward the edge. However, this affected zone is relatively narrow and would likely fall outside the image area when using smaller sensors (APS-C, MFT).
Center
Despite the less-than-ideal tube lens, the center remains reasonably sharp. The details of the test pattern are clearly recognizable, although they lack the brilliance seen in the previous image taken with the 200 mm tube lens. Fine circuit lines appear slightly softer, and microcontrast is reduced. This is due to undercorrection of the objective when used with too short a tube length—it is not designed for this image distance. Nevertheless, resolution remains solid, and there are no significant color fringes. Slight spherical aberration is visible.
Extended Center
More noticeable weaknesses begin to appear in the mid-zone: fine structures start to blur together, and contrast drops visibly. Some areas look slightly "milky," indicating a combination of spherical aberration and astigmatism. These issues become more pronounced with an incorrect tube length, as the lens’s corrective elements no longer function at their calculated focal plane. Here, it becomes clear that the optimization for a 200 mm tube length is a sensitive and critical parameter.
Edge Zone
Image quality in the corners is significantly reduced. Line structures lose their definition almost entirely. Coma-like distortions appear, and some patterns look warped or "bled out." This is a typical effect of using an incorrect tube length in combination with a large image circle (full-frame). Vignetting also becomes clearly noticeable—the outer fields are much darker than in the first image. However, chromatic aberrations remain largely inconspicuous, once again indicating strong chromatic correction in the objective design.
Overall Impression
The Mitutoyo M Plan Apo 5x can still produce a decent central image on a full-frame sensor even when used with a shorter tube (125 mm), but it suffers a significant loss of quality toward the edges. Field curvature, spherical aberration, and contrast loss become clearly visible—demonstrating how precisely this objective is optimized for a 200 mm tube length. It responds sensitively to deviations, as not only the magnification but also the focal positioning of the correction groups is affected.
Recommendation
For optimal results on full-frame sensors with this objective, a 200 mm tube lens should be used—preferably one of high optical quality (such as the Raynox DCR-250). Anything shorter leads to a visible departure from the optical ideal.
Comparison: Mitutoyo M Plan Apo 5x vs. Canon MP-E 65mm
The direct comparison with the Canon MP-E 65mm reveals in the cropped close-up that the Mitutoyo M Plan Apo 5x plays in an entirely different league. It delivers a level of detail sharpness that simply cannot be achieved with a standard full-frame camera lens—even when, as in the case of the Canon, it is a specialized macro optic optimized for close-range work and offers significantly higher line resolution (in lines per millimeter) than a conventional standard lens.
Mitutoyo M Plan Apo 5x on the left and, for comparison, Canon MP-E 65mm at 5x on the right – in this side-by-side comparison of two enlarged crops from the central image area, the sharpness advantage of the Mitutoyo becomes evident, even when compared to the already very sharp Canon MP-E. This is especially noticeable in the small square box structures.
Evaluation
The comparison image shown allows for a precise evaluation of the image quality delivered by two different lenses at a magnification of 5:1 on a full-frame sensor—on the left, the Mitutoyo M Plan Apo 5x; on the right, the Canon MP-E 65mm at its maximum extension and set to f/8. Both images capture the central portion of the frame and were produced using focus stacking to maximize depth of field.
In direct comparison, the Mitutoyo reveals superior detail reproduction. Fine structures of the test circuit are rendered sharply down to the smallest branches, with high microcontrast and clearly defined edges. There are no visible color fringes or contrast softening. Even tightly spaced lines remain well separated, indicating excellent correction of spherical aberration, astigmatism, and chromatic errors. The overall image character appears crisp, clear, and highly dimensional, thanks in part to the high numerical aperture (NA 0.14), achieving a level of optical quality only possible with highly corrected industrial objectives.
The Canon MP-E 65mm performs noticeably weaker in this comparison. Although the image was also stacked—and should therefore convey a strong impression of sharpness—it appears softer overall. Fine structures blur slightly, lines exhibit minor blooming, and the microcontrast is significantly reduced. Most notably, delicate details appear matte and slightly “milky.” Additionally, faint chromatic aberrations are present—such as magenta or cyan edges at high-contrast transitions—typical of lenses lacking apochromatic correction. Some of these shortcomings can be attributed to the chosen aperture: at a 5:1 magnification, the diffraction limit is already reached around f/4 to f/5.6. The f/8 setting used here visibly amplifies diffraction-related softness. Using f/4 would yield a slightly sharper result.
In summary, the Mitutoyo M Plan Apo 5x clearly outperforms the Canon MP-E 65mm in the central image area when used properly with a 200 mm tube lens. It delivers near-perfect rendering of fine details and remains free of distracting optical flaws. While the Canon MP-E 65mm remains unmatched in flexibility—as a compact macro zoom lens offering continuous magnification from 1:1 to 5:1—its optical performance at maximum magnification and smaller apertures does not reach the standard of a specialized industrial lens. For studio work demanding the highest levels of resolution and precision, the Mitutoyo remains the decidedly more capable choice.
Imaging Performance – 208 mm Tube Lens: Microprocessor
The following image shows a highly magnified crop of a microprocessor measuring 3 × 3 mm, captured with the Mitutoyo M Plan Apo 5x in its optimal configuration—that is, with a 200 mm tube lens on a full-frame sensor. This setup allows for a very precise assessment of the lens’s imaging performance across different areas of the frame, showcasing not only its sharpness and detail resolution but also offering an impression of its color rendering capabilities.
Clear, sharp details; somewhat low color contrast; no perceptible distortion in the corner areas, as the overview image was heavily cropped on all sides—since at this magnification, it did not fully cover the sensor.
Center
Image quality here is excellent. Even the finest structures on the silicon chip—such as transistor grids, circuit traces, and logic blocks—are rendered with outstanding sharpness and clarity. Lines are defined with extreme precision, without any visible blooming or color fringing. Microcontrast is high, even in densely packed areas. There are no signs of spherical aberration, longitudinal chromatic aberration, or loss of resolution. The overall impression is analytical—almost microscopic—which is characteristic of high-end plan apochromats with a high numerical aperture.
Extended Center
Image quality remains at a very high level in this zone. Fine detail continues to be cleanly rendered, though with a slight reduction in microcontrast compared to the absolute center. Even within the broader logical structures, all elements remain clearly distinguishable. The flatness of the focus plane in this region is excellent, indicating very low field curvature. Astigmatism and other tangential aberrations are not apparent in this area
Edge Zone
At the edges, a slight but noticeable drop in image performance becomes evident—though it remains on a generally high level. Sharpness decreases moderately, and the finest structures begin to merge slightly in particularly information-dense areas. Nevertheless, all key features and functional units on the chip remain clearly visible. There is no significant distortion, no chromatic aberration, and no vignetting. The edge softness presents more as a minor loss of fine resolution—typical for large sensor formats when using industrial lenses with a relatively limited image circle.
Overall Impression
The Mitutoyo M Plan Apo 5x demonstrates why it is considered a reference lens in scientific and industrial macro photography. When used with the correct tube length (200 mm) and a full-frame sensor, it delivers razor-sharp, distortion-free, and color-neutral rendering across the entire image field. Image quality in the center and extended center is outstanding; the slight sharpness falloff at the edges is system-related and minimal. For focus stacking, documentary micro-imaging, and high-resolution visualization of fine technical structures, this lens is an excellent choice.
Resolution Test
The Zeiss Resolution Test 300 allows the resolution of a microscope objective to be evaluated as a numerical value. While reading this value involves a certain degree of interpretation and is not entirely precise (see details here), it still provides a useful overall impression of the lens’s fine rendering and detail reproduction capabilities.
The resolution value in the image center, shown here in the two outer fields, was measured at 360 line pairs per millimeter (lp/mm).
Conclusion
The Mitutoyo M Plan Apo 5x delivers nearly uncompromising optical performance—especially in the image center and when used in the correct optical configuration. It offers exceptionally high detail resolution, outstanding microcontrast, and apochromatically clean color rendering—qualities that only a few lenses in this price range can match. Its full potential is realized when paired with a tube lens of exactly 200 mm focal length, as specified by the manufacturer. Under these conditions, image aberrations across the central field—even on a full-frame sensor—are negligibly small.
While Mitutoyo officially specifies the objective for an image circle of 30 mm, designed for sensors in the 2/3-inch class, it still delivers impressive results on significantly larger formats such as APS-C, Micro Four Thirds, or even full-frame—as long as the focal plane remains within the extended central area. Only at the extreme corners of a full-frame sensor does a slight loss of sharpness appear, which is quite moderate and usually only noticeable with full-field structured subjects. A more critical drop in image quality occurs when the tube lens focal length is significantly reduced—e.g., to 150 mm or even 125 mm—where the image circle shrinks and edge softness and contrast loss become much more apparent.
For those seeking maximum detail resolution, the more expensive HR version may be a worthwhile alternative—though its strengths lie more in higher numerical apertures and even larger image fields. For typical applications in macro photography, documentation, scientific imaging, or industrial component inspection, the Mitutoyo M Plan Apo 5x remains one of the best options available—even when used on a full-frame sensor. Its edge limitations should be understood, but they quickly become irrelevant when the subject—like in most cases—is centered in the frame.
In short: this objective sets a benchmark in its class—and not just for small-sensor systems. With careful handling, proper tube lenses, and a stable setup, it rewards the user with image quality far beyond what traditional loupe objectives or macro zoom lenses can deliver.
Advantages
Extremely long working distance, high image sharpness and detail accuracy, excellent color correction, parfocality within the objective series—allowing for easy lens swapping.
Disadvantages
High purchase price, uncommon thread size requiring a special adapter (e.g., www.stonemaster-onlineshop.de), slight edge softness when using a shorter tube lens (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