Lens Spotlight
Mitutoyo M Plan Apo 5x HR
The Mitutoyo M Plan Apo 5x HR is a high-resolution variant of the widely used M Plan Apo 5x.
The Objective
The Mitutoyo M Plan Apo 5x HR is a lens designed for metallurgical applications, but its resolution significantly exceeds what would typically be expected in the mid-price range.
The Mitutoyo M Plan Apo 5x HR is part of a parfocal objective series with an identical housing diameter.
A few words about the entire “M Plan Apo” series from Mitutoyo: This is a line of objectives with varying magnification ratios, all of which are parfocal—meaning they share the same overall housing length and working distance. The housing diameter and threading are also identical throughout the series, with the exception of the 1x objective, which has a different diameter.
The main advantage of this parfocality becomes apparent when used on specialized microscopes, where a fixed-length camera extension—typically with a built-in tube lens—is mechanically configured for all objectives, as is common in laboratory microscope setups. However, this parfocality is also extremely useful for focus stacking setups, as it allows for effortless switching between objectives within the series without requiring adjustments to the rest of the setup—something that’s highly convenient in practical use.
A long working distance is essential for many metallurgical applications, particularly because the lighting must often come in from the side. This is a key difference from most microscope objectives designed primarily for laboratory use (medicine, biology, etc.), where transmitted light is the norm, and a long working distance is not only unnecessary but can even be a hindrance.
Although the Mitutoyo M Plan Apo 5x HR featured here was originally developed for use with specialized microscopes, its long working distance makes it perfectly suited for focus stacking setups, where it is mounted on a full-frame camera along with the required tube lens. The extended working distance greatly simplifies the task of lighting the subject.
The HR variant has a slightly longer housing than the standard version.
View of the front and mounting side of both objectives
The Manufacturer
The manufacturer is the Japanese company Mitutoyo, which—alongside these specialized objectives—produces a wide range of testing and measurement instruments for metallurgical applications. In Germany, the objectives are offered by companies such as Edmund (www.edmundoptics.de) and Novoflex (www.novoflex.de).
When this objective series was introduced, it set new standards by combining a long working distance, high numerical aperture (NA)—and thus high detail resolution—with excellent color correction and minimal distortion, even to the edges of its relatively large 30 mm image circle. Additionally, as mentioned earlier, all objectives in the series are parfocal. This was only made possible by the extremely large lens diameter, which pushed both the size and weight of these objectives to previously unmatched levels.
While the M Plan Apo objectives in this series without the “HR” label do not push the limits of what is physically possible in terms of numerical aperture and resolution, the HR series (high resolution) was designed to do exactly that. However, since optical engineers are not magicians and cannot override the laws of physics, this increase in imaging sharpness comes at a cost—not just at the point of sale, but in other ways as well. Sharpness, working distance, and image circle—particularly edge performance—are all interrelated, and adjusting one parameter inevitably impacts the others (see details in this article). In short: no gain without compromise. To counterbalance such trade-offs, the manufacturer must go to great lengths—whether through higher-quality lenses, superior coatings, or other advanced measures—and that, of course, drives up the price.
When looking through the lenses from the front, there is hardly any visible difference. However, from the rear, it becomes clear that the HR variant has a noticeably wider aperture angle (HR variant on the left in each case).
When increasing image sharpness in the center, one might reasonably expect either a reduced working distance or a decline in image quality (sharpness, distortion control, chromatic accuracy) in the corners—or perhaps even both. And indeed, the working distance of the HR optic featured here is shorter than that of the non-HR version. However, this is by design, as the housing is longer, and together both values are meant to total 95 mm. This test aims to determine how the image quality holds up in the corners and whether the HR version reveals any weaknesses compared to the standard model. Naturally, we’re also interested in just how much sharper the HR variant actually is—especially considering its purchase price is several times higher than that of the base version.
This lens was kindly provided for testing by Dr. Kristian Peters.
A look at the front lens reveals that the HR variant uses significantly more effective coatings, as reflections are much lower. This greatly enhances contrast performance by reducing stray light effects.
Technical Specifications
Magnification: 5x
Numerical Aperture: 0.21
Infinity-corrected optics (requires tube lens)
Compatible Tube Lens Focal Length: 200 mm
Thread Diameter and Pitch: M26 x 36 TPI
Weight: 285 g
Housing Length: 69.5 mm
Housing Diameter: 34 mm
Parfocal Distance (Housing Length + Working Distance): 95 mm
Exit Pupil Diameter: 18 mm
Focal Length: 40 mm
Working Distance: 27.0 mm
Resolution: 1.3 µm
Depth of Field: 6.2 µm
Imaging Performance – 208 mm Tube Lens
The following test images illustrate the imaging performance of the objective. The first is 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.
Test image at nominal magnification (DCR 150), with frame markers for the following cropped enlargements – very good sharpness, no visible vignetting, free of chromatic aberrations, and extremely slight pincushion distortion toward the image corners, which is barely visible and only measurable.
The central cropped close-up reveals, as expected, brilliant detail sharpness without chromatic aberrations.
In the corner crop of the full-frame image, a slight decrease in detail sharpness can be seen in the outer edge area (here in the upper left), most noticeably in the square elements. The mild pincushion distortion also becomes more apparent toward the corner. The sensor’s 43 mm diagonal slightly exceeds the objective’s image circle, but these effects would likely be absent on a smaller sensor (APS-C, MFT). Even on full-frame, the impact is minimal and likely insignificant at this level.
Center
The imaging performance in the center is simply outstanding. Even the finest lines and structures of the test target are rendered crystal-clear, high in contrast, and completely free from softness. Microcontrast is visibly enhanced compared to the standard M Plan Apo 5x. Edges are razor-sharp, with no blooming or halos. Even the finest elements are cleanly separated, indicating excellent correction of all monochromatic and chromatic aberrations. The HR design fully demonstrates its strengths here—delivering what is likely the best central optical performance currently available in the 5x industrial macro category.
Extended Center
Quality remains excellent in the mid-zone. Even in areas of high information density—such as dense circuit patterns or finely segmented edge zones of the test fields—the lens shows no meaningful degradation. The image remains crisp, with cleanly separated lines and no loss of contrast or onset of softness. Field flatness is very good—no signs of astigmatism or field curvature are visible, even when the focal plane varies slightly across the frame. This suggests a clearly improved flat-field correction compared to the standard version.
Edge Zone
In the edge region, the HR objective shows its real strength: unlike the standard version with NA 0.14, which exhibits noticeable quality drop-off at the edges, the HR version maintains impressively high performance here as well. Sharpness decreases only minimally—a slight softening is detectable, but details remain clearly defined and never appear muddy or distorted. Even the corner areas are nearly free from chromatic aberration and coma, which is remarkable considering a full-frame sensor with a 43 mm diagonal is being used, while the specified image circle is only 30 mm. Apparently, the optical reserves of this HR model allow for a practical expansion of the usable image field far beyond its original design specification.
Overall Impression
The Mitutoyo M Plan Apo 5x HR is a high-precision specialty objective that performs exceptionally well even on a full-frame sensor. It surpasses the already excellent standard version in every aspect: higher microcontrast, finer detail rendering, significantly improved edge and corner performance, and overall more uniform image quality across the entire frame. The numerical aperture of 0.21 plays a major role in this performance—it not only provides higher theoretical resolution but also delivers noticeably greater structural fidelity on real-world subjects.
For those with the highest demands for image quality—especially in scientific documentation, material analysis, or technical microphotography—this objective offers one of the best tools available, particularly for full-frame use. The Mitutoyo M Plan Apo 5x HR sets a new benchmark and is highly recommended for any application where uncompromising image quality is essential.
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 mentioned Mitutoyo series tolerate this approach to varying degrees, and this test aims to show what quality compromises—if any—can be expected when using the Mitutoyo M Plan Apo 5x HR under these conditions.
Test image with DCR 250: The shorter tube lens focal length results in a lower magnification, and with this combination (for which the objective was not designed!), the full-frame sensor more noticeably exceeds the usable image circle. Pincushion distortion becomes clearly more pronounced in the corners, and sharpness also drops off significantly in those areas.
In the central cropped close-up of the full-frame image, detail sharpness is consistent and good. No chromatic aberrations are visible, and the image shows no noticeable distortion.
In the enlarged corner crop of the full-frame image, both distortion and blurring increase noticeably toward the edge—though not quite as dramatically as with the non-HR version. However, this affected zone is so narrow that it wouldn’t appear on smaller sensors (APS-C, MFT), and even on a full-frame sensor, it’s unlikely to matter with center-weighted subjects.
Center
In the center, image performance remains surprisingly strong—despite the significant underdriving. Circuit structures are still clearly distinguishable, and lines appear mostly sharp, though with slightly reduced microcontrast compared to optimal operation. The extreme precision the HR objective demonstrates at 200 mm is somewhat diminished, but still remains at a very high level. Central resolution remains high, although there’s a slight “matte” appearance—an indication of emerging spherical aberration due to shifts in the corrective elements within the lens system.
Extended Center
In the extended center zone, the loss in quality becomes noticeably more apparent. Fine structures begin to merge, local contrast visibly decreases, and the image takes on a softer overall impression. Lines appear less defined and in some cases slightly blurred. This is where the shortening effect of the tube lens becomes more pronounced: the image field contracts, projection onto the sensor becomes distorted, and correction for field curvature and astigmatism no longer fully applies. The plane of sharp focus also seems to tilt slightly—suggesting asymmetric distortion.
Edge Zone
In the corners and extreme outer regions, image quality is significantly limited. Contrast drops sharply, fine structures appear smeared, and in some areas, lines are only visible as blurry gray zones. Optical correction is largely ineffective here, as the altered tube length leads to noticeable loss of field flatness and a dramatic reduction in resolution. Coma-like flare and slight distortions are visible. However, even here, chromatic aberration remains surprisingly low—thanks to the high-end apochromatic correction of the HR objective.
Overall Impression
Even under less-than-ideal conditions, the Mitutoyo M Plan Apo 5x HR demonstrates impressive optical resilience. In the center, image quality remains at a high level, albeit without the legendary precision the lens delivers with a 200 mm tube lens. From the mid-zone outward, the quality loss becomes increasingly evident, and at the edges, it is significant. The results clearly highlight how precisely this objective is tuned to the correct tube length—and how sensitively it reacts to deviations. For image applications with centrally placed subjects, the lens can still deliver usable results at a magnification of approximately 3.1:1 with a shorter tube, but anyone aiming to fully exploit its capabilities—especially across a full-frame sensor—should definitely adhere to the specified 200 mm.
Overall, this test image confirms that the HR model not only offers peak optical performance under ideal conditions but also outperforms the standard version noticeably even in suboptimal setups with a shortened tube—proof of the exceptional optical quality and performance headroom of this objective.
Comparison: M Plan Apo 5x – M Plan Apo 5x HR – M Plan Apo 10x
The direct comparison between the Mitutoyo M Plan Apo 5x HR and the non-HR version shows in the cropped close-up that the HR plays in an entirely different league. It delivers a level of detail sharpness reminiscent of what a Nikon CF Plan Apo produces in the image center—though here with a significantly larger image circle.
While both of these objectives were used with the Raynox DCR 150 tube lens (208 mm focal length) for this comparison, a test with the Mitutoyo M Plan Apo 10x using a shorter tube lens was intended to see whether a similarly high level of detail rendering could be achieved. After all, this lens has a numerical aperture of 0.28 (compared to 0.21 for the 5x HR). However, this setup pushes the 10x outside of its ideal operating range—its so-called "sweet spot"—since it’s being used with a shorter tube lens and reduced extension. The direct comparison shows that while this approach yields more detail than the 5x with the DCR 150, the imaging sharpness of the 5x HR remains completely unmatched.
The already sharp-rendering Mitutoyo M Plan Apo 5x (left) is vastly outperformed by the HR variant (center), and even the 10x with a shorter tube lens focal length cannot come close to matching this level of image sharpness (all crops are from the image center, highly upscaled).
Image left – Mitutoyo M Plan Apo 5x (NA 0,14, tube lens 208 mm)Resolution is solid, and typical structures are clearly visible, but microcontrast is noticeably lower in direct comparison. Fine lines appear slightly bloomed, and grayscale gradients are somewhat flat. Especially along diagonal edges (e.g., upper left corner of the “765” field), there are subtle resolution losses and the onset of softness. The image is good—but not a leader when compared to the other two. This confirms what was already evident from earlier test shots: the standard 5x version performs well in the center but is not optically maximized. Summary: Good, but clearly weaker than the HR version.
Image center – Mitutoyo M Plan Apo 5x HR (NA 0,21, tube lens 208 mm)This image is significantly clearer and sharper. Microcontrast is outstanding, fine circuit traces and transitions are cleanly separated, with no blooming or smearing. Lines are crisp and well-differentiated, and the gray areas between structures appear smoother and more detailed. The HR version clearly delivers the best result here: highest fidelity in detail, excellent tonal purity, and visibly better edge sharpness. It stands as the optical reference in this comparison. Summary: Optically flawless—maximum image quality with perfect balance.
Image right – Mitutoyo M Plan Apo 10x (NA 0,28, tube lens 125 mm)
Surprisingly strong—especially considering the lens is designed for 10x at 200 mm tube length but is throttled down here to around 6.25x. Still, the lines are crisper than with the standard 5x, microcontrast is better, and even the tiniest details in the black areas remain visible. However, the rendering feels slightly harsher, with a subtle tendency toward microscopic "ringing" at the edges. The sharpness is a bit technical—not quite as harmoniously balanced as with the 5x HR. Fine brightness speckles and delicate tonal gradations appear slightly less nuanced. It’s an excellent image—but it lacks the final touch of elegance and refinement that defines the 5x HR. Summary: Strong, better than the standard 5x, but with a slightly more "technical" look.
Overall Impression
The Mitutoyo 10x at 125 mm tube length visibly outperforms the standard 5x, particularly in terms of sharpness and contrast. It comes close to the performance of the 5x HR but doesn’t quite match it. The HR version remains superior—it combines maximum sharpness with an exceptionally smooth image character, excellent microcontrast, and natural tonal differentiation.
When it comes to maximum center performance with professional reproducibility, the 5x HR remains the top choice. However, the 10x at 125 mm is a very interesting and capable alternative—especially in situations where a touch more magnification is desired without compromising the image field.
Imaging Performance – 208 mm Tube Lens: Microprocessor
The following image shows a highly magnified crop of a microprocessor measuring 3 × 3 mm, captured using the Mitutoyo M Plan Apo 5x almost in its optimal configuration—with a 208 mm tube lens on a full-frame sensor. This setup allows for a very precise evaluation of the lens's imaging performance across different areas of the frame, revealing not only its sharpness and detail resolution but also providing an impression of its color rendering capabilities.
The 3 mm wide microprocessor shows clear and sharp details
This crop of the 3 mm wide microprocessor represents approximately 1.6 millimeters of image width and shows not only strong color contrast but also brilliant sharpness.
This single view shows a magnified crop of the full chip in impressive optical quality. What stands out is the remarkable structural clarity across the entire image field: even the finest circuit details appear sharp and high in contrast, with neutral and well-differentiated color reproduction. There are no distracting chromatic aberrations, no blooming in bright areas, and no noise in dark zones. Particularly noteworthy is the excellent edge definition—transitions between metal, silicon, and substrate structures remain cleanly separated, without any edge softness or fraying.
The consistent brilliance across the entire visible field indicates perfectly flat optical correction—typical of a high-end apochromat with a high numerical aperture. The rendering of the bond pads on the right side of the image is also free from glare, with well-resolved structural details visible within the contact surfaces.
Comparison Mitutoyo M Planapo 5x HR – M Planapo 5x
The fine structures within the microprocessor also lend themselves well to a comparison between the HR and the standard version—and once again, the HR variant proves vastly superior. This becomes immediately apparent when looking at the square contact pads of the processor, but the tiny internal details also make it clear that the outrageously expensive HR version is in a class of its own.
The Mitutoyo M Plan Apo 5x HR in direct comparison with the standard version, the M Plan Apo 5x
This comparison clearly highlights the advancements the HR model offers over the standard version.
Resolution and Microcontrast
On the left (5x HR), even the tiniest grids and logic elements within the circuitry are clearly visible and sharply separated. On the right (standard 5x), the same structures appear softer, with weaker edge definition and reduced tonal dynamics. The overall impression is duller and less finely rendered.
Edge Sharpness and Detail Separation
In the HR image, circuit traces show precise black-and-white contrast, without fringing or blurring at transitions. In contrast, the same structures in the standard objective appear slightly softened. Lines begin to merge in densely packed areas.
Tonal Depth and Surface Smoothness
The surfaces in the HR image appear calmer, more homogeneous, with greater tonal differentiation—especially in the metallic contact zones. In the right image (standard 5x), subtle fluctuations in brightness and grainier transitions can be observed.
Chromatic Aberrations
Both images show generally excellent color correction, but the HR objective remains even more neutral—particularly in high-contrast transitions, where it exhibits no color fringing or CAs, while the standard model shows minimal color shadows under extreme magnification.
Overall Assessment
The images confirm once again: the Mitutoyo M Plan Apo 5x HR outperforms the standard 5x model in all key aspects of image quality. It offers higher resolution, greater microcontrast, cleaner edges, and an overall calmer, more pristine image. For demanding applications such as precise documentation of technical structures (e.g., microprocessors, MEMS, micromechanics), the HR model is clearly the superior choice—even on a full-frame sensor.
For anyone looking to extract the maximum amount of information from a subject—whether for research, technical analysis, or scientific publication—the 5x HR represents a reference-grade optic that is currently hard to surpass. The standard model remains a good, but visibly inferior, alternative by comparison.
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 interpretive, not entirely precise, and highly dependent on the resolution of the camera sensor (see details here), it still provides a general impression of fine rendering and detail reproduction. With the HR objective presented here, this resolution test becomes even more challenging than with the non-HR version—despite using a high-resolution 45-megapixel sensor—because the smallest resolvable line spacings are finer and thus represented by fewer pixels, making them harder to distinguish. In general, objectives with 5x magnification or less ideally require sensors with smaller pixel sizes for this type of evaluation.
The value for resolvable line pairs is clearly higher at 450 lp/mm compared to the non-HR version (360 lp/mm). However, using a camera sensor with smaller pixels might allow for an even higher value to be measured.
Conclusion
The Mitutoyo M Plan Apo 5x HR is a no-compromise, high-performance optic and ranks among the best industrial objectives available for high-resolution macro photography. Its image quality clearly surpasses even the already excellent standard version of the M Plan Apo 5x—delivering superior detail resolution, microcontrast, edge sharpness, and fine structure differentiation. Once you’ve experienced the HR model in practical use, it’s hard to go back to the non-HR version—even if you previously found it more than sufficient.
When used as intended with a 200 mm tube lens—or with a slightly shorter alternative like the DCR 150—it delivers outstanding results even on a full-frame sensor. A slight loss of sharpness at the extreme edges is measurable, but in real-world use, it’s rarely relevant. Only when the tube lens focal length is significantly shortened (e.g., DCR 250), thus operating outside the specification, do notable limitations appear in the outer image zones—especially with subjects containing fine structure all the way to the corners. These effects are irrelevant for smaller sensor formats like APS-C or Micro Four Thirds.
Contrary to the manufacturer’s official claim that the lens is designed for sensors up to 2/3 inch, real-world use shows that it performs exceptionally well even on full-frame sensors—especially when the subject is centered in the frame, as is typical in macro photography (“fly-head scenario”). In such cases, the outer sensor zones are visually unused or serve merely as background blur.
Additionally, the numerical aperture of 0.21 gives the 5x HR a significant resolution advantage over the standard version (NA 0.14), which becomes immediately visible at identical magnification—not just in the center but across much of the image field. Its optical correction is impressively flat, free of color fringing, and exhibits a very consistent contrast profile.
All in all, the Mitutoyo M Plan Apo 5x HR is a lens for those who refuse to compromise in documentary macro work—and are willing to operate a specialized setup to achieve the highest optical performance. For anyone seeking to extract the maximum possible information from small structures, this lens represents a true reference class.
Advantages
Extremely high image sharpness, long working distance, excellent color correction, parfocality within the objective series—allowing for easy lens changes.
Disadvantages
Very high purchase price, uncommon thread size requiring a special adapter (e.g., RAF Camera or www.stonemaster-onlineshop.de).
Daniel Knop, www.knop.de, www.danielknop.eu