50x Lens Shootout
Mitutoyo M Plan Apo 50x
HLB Plan Apo 50x
Two objectives with nearly identical specs—both offering 50x magnification, a numerical aperture of 0.55, and designed for infinity-corrected tube optics—suggest a comparable imaging performance on paper. But how significant are the actual differences between these two lenses in practice? To explore this question, I conducted a systematic comparison between the Mitutoyo M Plan Apo 50x NA 0.55 and the more budget-friendly HLB Plan Apo 50x NA 0.55.
Both objectives originate from the field of metallurgical microscopy, meaning they are optimized for reflected light and are frequently discussed among macro photographers—especially for use in focus stacking—as powerful high-magnification options. The goal of the following comparison is not only to evaluate the technical characteristics of each lens but also to assess their real-world performance in photographic microscopy. This includes image quality, usability, and how each performs with different sensor formats, all under as identical conditions as possible.
The results are intended to provide a well-grounded basis for decision-making—particularly in answering whether the higher price tag or the potential cost savings actually translate into a practical advantage in everyday photographic use.
Mitutoyo M Plan Apo 50x (left) and HLB Plan Apo 50x (right) — both were designed as microscope objectives for metallurgical applications and are ideally suited for focus stacking work.
Design and Build Quality
At first glance, both objectives appear nearly identical. They share the same thread format (M26 x 36 TPI), have almost the same housing diameter, and fit easily into standard adapters, bellows, or microscope mounts. They also differ only slightly in length. However, upon closer inspection and during practical use, some differences become apparent that go beyond mere shape.
The Mitutoyo objective feels slightly more refined overall: its surfaces are made of matte-anodized aluminum, the edges are precisely finished, and the threading operates smoothly and accurately.
The HLB objective is noticeably heavier, which suggests different materials or more substantial internal components.
The labeling on both is not engraved but applied as raised lettering. A subtle difference can be seen at the front lens: under sidelight, the HLB shows slightly weaker reflections compared to the Mitutoyo, which may indicate a slightly different coating or lens geometry. Whether this has a meaningful impact on image quality remains to be seen.
Overall, both objectives give a high-quality impression. The Mitutoyo conveys a sense of precision craftsmanship, while the HLB has a more robust, heavier character — both are well-suited for photographic use but present different aesthetic and tactile qualities.
The Mitutoyo (left) is slightly slimmer and lighter, though otherwise these two optical powerhouses are very similar.
Practical handling in the setup
In a real-world focus stacking setup, both objectives can be integrated equally well. They share the same thread diameter, the same tube length, and are parfocal—allowing for lens changes without any adjustment. This is a major advantage when capturing image series at varying magnifications.
Because of their identical optical design and intended pairing with a 200 mm tube lens, both yield an effective magnification ratio of 50:1. Mounting on a bellows or extension rings with a macro rail is straightforward. While the HLB lens is noticeably heavier, this poses no practical limitations as long as the setup is stable and free of mechanical play.
Day-to-day handling reveals subtle but noticeable differences. With the Mitutoyo, precise centering is immediately apparent—the optical axis sits very stably within the light path, which translates into a more sensitive focus response and accurate positioning. The threading is smooth and play-free, and the lens mount is machined precisely enough to retain its alignment even after repeated mounting and unmounting.
Mounting the HLB is also problem-free. Some users have reported slight axial play when screwing it in, which could theoretically lead to minor angular deviations—especially if the adapter is not perfectly flat. However, this effect could not be clearly reproduced in the test unit used here. The heavier HLB does shift the center of gravity slightly on some rails or holders, particularly when mounted vertically. While this doesn’t measurably tilt the focus plane, positioning may feel just a touch less precise.
One clear advantage of both lenses is their generous working distance. Despite the high magnification, there is plenty of room for effective lighting. This facilitates the use of side lighting or diffused LED illumination without annoying reflections from the lens barrel. This is particularly valuable for subjects with delicate surface features—such as fine hairs, pollen grains, scales, or crystal filaments—that can be disrupted by even minimal vibrations or air currents. Likewise, objects with protruding elements such as insect antennae, flower stamens, or jagged edges benefit from the spacing: Lighting setups can be positioned freely, without interference from reflectors or the lens itself.
Anyone working regularly with lifelike specimens, insects, or complex textures will quickly come to appreciate the extra space around the front element. Both objectives offer significantly more freedom than many older microscope lenses with shorter working distances, and they allow for the unrestricted use of diffusers, reflectors, or angled dual lighting—an often underestimated practical benefit.
Imaging Performance – 200 mm Tube Lens
At the beginning, there is an uncropped image of a microstructured wafer taken with the Mitutoyo M Plan Apo 50x and the HLB Plan Apo 50x, each using a 200 mm tube lens and delivering an approximate magnification ratio of 50:1. The tube lens is of very high quality and closely matches the specifications of the ITL 200 from Thorlabs. These overview images provide a general impression and clearly reveal any possible distortions. They are followed by side-by-side comparisons showing cropped sections of these images—Mitutoyo on the left, HLB on the right.
Center
Both objectives deliver high resolution in the center, with cleanly defined edges, well-delineated contrast lines, and clearly distinguishable structures within the metallic grids. However, in direct comparison, the HLB exhibits slightly higher microcontrast in the center. Fine textural differences (e.g., in the granularity of the rectangular contact areas) appear a bit crisper and more three-dimensional. The Mitutoyo also provides excellent resolution but with slightly softer contrast transitions—which may be perceived as either more pleasant or less defined, depending on the subject.
Extended Center
In this zone, the HLB again holds a slight advantage in terms of detail contrast and edge sharpness. The spacing between structures tends to be a bit more clearly separated in the HLB image, while the Mitutoyo shows slightly more blending in those areas. The differences are subtle but noticeable in direct comparison—especially in more complex regions with many contrast edges.
Edge Zone
Here, the balance shifts: the Mitutoyo lens demonstrates a noticeably more uniform sharpness distribution all the way to the image edge. The right edge of the frame and the circular structures in the bottom right corner of the full image appear distinctly clearer with the Mitutoyo, showing no visible softening. In contrast, the HLB exhibits a more pronounced loss of sharpness in this area—especially along the vertical structure on the right and the rounded elements in the lower right, which appear softer, slightly blurred, and in some cases mildly distorted. Chromatic correction also seems to diminish slightly in this zone, though no severe color fringing is visible.
The left half of the full image from both objectives in comparison; this view spans from the center (mid-right in both individual images) to the image edge and corners (left side in each), making it possible to detect any distortion.
In the central cropped enlargement, both lenses show very high detail sharpness without chromatic aberration. On the right, the HLB delivers slightly better color contrast and finer detail rendering than the Mitutoyo on the left.
In the corner crop of the full-frame image, both objectives exhibit a slight loss of detail sharpness—but here, the Mitutoyo clearly comes out ahead. The HLB struggles more noticeably in this area.
Stray Light and Black Level
The Mitutoyo displays slightly deeper blacks in the background, with a bit less of a milky haze. This suggests slightly better control of stray light or internal reflections. With the HLB, black areas appear a touch brighter and, under high magnification, show a faint "clouding" that may stem from internal reflections or stray light from the front optics. However, this is only noticeable under very critical inspection.
Overall Impression
The HLB Plan Apo 50x delivers exceptionally high detail rendering in the center and extended center area, outperforming the Mitutoyo by a small but noticeable margin in those zones. However, in the outer image areas, the Mitutoyo shows clearly superior correction, with more uniform sharpness distribution and less distortion. Therefore, users primarily working in the image center, using smaller sensors, or applying heavy cropping might prefer the HLB. Those needing a larger, evenly usable image circle—such as with full-frame sensors or for capturing wide structures—will benefit from the more consistent field performance of the Mitutoyo.
Imaging Performance – 125 mm Tube Lens
In this second test series, each lens was again used to capture an uncropped image of the wafer at the outset—but this time with a 125 mm tube lens, resulting in a reproduction ratio of approximately 31x. Here, both objectives exhibit a noticeably different character compared to their performance with a 200 mm tube lens. The optical systems are being operated outside their specified compensation range, which is clearly reflected in the imaging performance. As before, the series continues with side-by-side comparisons of cropped sections from these images, with the Mitutoyo on the left and the HLB on the right.
In this second test series, each lens again begins with an uncropped image of the wafer—this time, however, using a 125 mm tube lens, resulting in an approximate magnification of 31x. Under these conditions, both objectives exhibit noticeably different characteristics compared to their performance with a 200 mm tube lens. The optical systems are being operated outside their specified compensation range, and this clearly affects imaging performance. As before, the test continues with side-by-side comparisons of cropped sections from the captured images, with the Mitutoyo on the left and the HLB on the right.
Center
In the center, the HLB Plan Apo 50x again shows crisp sharpness with high microcontrast. However, diffraction rings or light streaks along bright edges become noticeably apparent. These star-shaped artifacts are caused by overcorrection or internal reflections resulting from suboptimal light paths—an effect that is far more pronounced in the HLB than in the Mitutoyo. While the Mitutoyo renders the center with slightly softer definition, it remains optically cleaner and free from stray light effects.
Extended Center
The differences become more pronounced moving outward. The Mitutoyo maintains better sharpness across the mid-zone, despite its slightly softer rendering. The HLB may appear richer in texture, but it increasingly suffers from light fringing and local contrast exaggeration along the edges of metallic structures. This is particularly noticeable in the lower right quadrant, where visible halos form—likely due to insufficient correction of spherical aberration at this reduced tube length.
Edge Zone
At the edges, the Mitutoyo clearly outperforms its competitor. While sharpness does diminish, it does so in a controlled manner: lines remain discernible, and contrast does not collapse entirely. The HLB, on the other hand, exhibits a significant drop in sharpness, accompanied by chromatic noise and reflective patterns indicating light path miscompensation at the shorter tube distance. Fine structures along the bottom edge and circular elements show strong softening, sometimes with exaggerated color fringes.
The left half of the full-frame image from both objectives in comparison; this view includes everything from the center (located mid-right in both individual images) to the image edge and corners (on the left), making any distortions clearly visible.
In the central cropped magnification, both objectives already show a slight reduction in detail sharpness.
In the corner crop of the full-frame image, both objectives are pushed beyond their limits—though the Mitutoyo handles the reduced tube lens focal length somewhat better than the HLB.
Overall impression
Reducing the tube lens to 125 mm has a negative impact on both objectives, but the Mitutoyo handles the deviation from the optimal configuration noticeably more confidently. It remains overall calmer and more controlled, with a gradual loss of sharpness. The HLB objective, on the other hand, clearly shows signs of being overstrained under these conditions: image defects that were barely noticeable at 200 mm now become obvious—especially in the peripheral zones, where the optical correction rapidly breaks down.
For those intending to use the objective with a shortened tube lens—e.g., to reduce the magnification—the Mitutoyo offers somewhat more stable image performance. While the HLB delivers impressive detail rendering in the center at optimal tube length, it loses precision more quickly under altered conditions.
Imaging Performance – 200 mm Tube Lens: Microprocessor
In the third comparison series—captured using a 200 mm tube lens on a modern smartphone microprocessor measuring 3 x 3 mm—the subtle yet critical differences between the two objectives once again become apparent, especially in the rendering of complex structural details.
Center
Both objectives deliver high resolution with excellent detail reproduction in the center. At first glance, the HLB Plan Apo appears slightly more brilliant—particularly in finely structured areas with strong local contrast. The gold-colored conductor paths are especially well defined. In contrast, the Mitutoyo offers slightly softer gradation, but with an extremely balanced tonal distribution that clearly differentiates even the smallest nuances in the metallic reflective surfaces. Notably, the Mitutoyo shows fewer internal reflections or glare bloating in the brightest highlights.
Extended Center
The HLB continues to provide high resolution in this region, though some instability begins to appear—e.g., in very fine line grids or densely structured areas. Some highlights appear slightly exaggerated, possibly due to lower stray light suppression or minor unevenness in field correction. The Mitutoyo maintains a calmer rendering. Fine lines appear more “structurally stable,” especially in grid-like patterns or overlapping lattice structures. The difference is small but noticeable upon close inspection.
Edge zone
This is where the typical strength of the Mitutoyo optics comes into play: sharpness distribution across the full image field is more consistent. The outer regions show virtually no visible aberrations—no softening or chromatic effects. The HLB, however, shows a slight softness on the far right edge, with the first signs of blur and chromatic shift becoming evident under high magnification—particularly on bright lines, which tend to “bleed” slightly or lose brilliance.
The microprocessor shown here spans a full width of 3 mm, slightly cropped at the top and bottom. The frames indicate the areas shown in the following image excerpts (note: this overview image was not captured using the Mitutoyo M Plan Apo 50x).
A 0.25 mm-wide excerpt from the extended center is rendered with fantastic clarity by both objectives. In this comparison, the HLB (right) appears slightly more brilliant and crisper than the Mitutoyo (left).
A further excerpt from the previous image—also from the extended center—shows a 0.12 mm-wide section of the original subject, with no image processing applied. The rendering performance of both objectives is simply impressive.
Color Reproduction and Reflection Behavior
Both objectives provide similarly good reproduction of the warm gold tones on the processor. However, some differences are noticeable: the Mitutoyo delivers a slightly more neutral light distribution, while the HLB appears marginally more contrast-rich but occasionally a bit overdriven in very bright zones. Especially on metallic reflective surfaces, the HLB tends to show more localized blooming—likely due to slightly stronger internal reflections.
Overall Impression
This scene highlights that the Mitutoyo objective offers more consistent image quality across the entire field when dealing with complex, large-area structures. The HLB objective, on the other hand, continues to impress with its high-contrast, brilliant rendering—visually even slightly outperforming the Mitutoyo in the image center. However, in the peripheral areas—particularly when using large sensors or capturing fully filled image fields—it shows slight weaknesses. For applications requiring full-field use, the Mitutoyo remains the more balanced choice overall. For highly center-focused detail work, however, the HLB can deliver a visually striking result—provided the lighting is precisely controlled and well diffused.
Behavior When Varying the Tube Lens Focal Length
Both objectives are designed for use with a 200 mm tube lens. In this configuration, they achieve their specified magnification ratio of 50:1 along with optimal optical correction. However, not every user works with precisely this focal length—whether due to space constraints, a desire for lower magnification, or to expand the field of view. For this reason, a second test series was conducted using a shorter 125 mm tube lens (Raynox DCR-250), which corresponds to an approximate magnification of 31:1.
In this configuration, the two objectives responded quite differently. The Mitutoyo M Plan Apo 50x reacted moderately: while overall sharpness decreased slightly, the image field remained homogeneous. Even at the edges, line reproduction stayed largely consistent, structures remained recognizable, and distortion was minimal. Color aberrations were not significant, and the overall image appeared optically calm. The reduction in tube lens focal length led to a visible but evenly distributed drop in quality—predictable and acceptable in practice, especially when using smaller sensors.
The HLB Plan Apo 50x responded much more critically to the altered tube optics. While it still produced very high detail resolution with strong contrast in the center, noticeable limitations emerged toward the image edges. Zones of significantly reduced sharpness appeared, sometimes accompanied by chromatic fringing, halos along bright edges, and localized blooming. The image field appeared uneven, and the outermost edges were in some cases unusable. Highlight areas showed pronounced flaring, which under close inspection resembled diffraction ring patterns—suggesting that the internal light path was operating outside the lens’s corrected range.
In short: while the Mitutoyo maintains a controlled, albeit reduced, performance level when using a shorter tube lens, the HLB reaches its limits. Users who plan to work with variable tube configurations or frequently use shorter focal lengths—either to lower magnification or for spatial reasons—will be better served by the Mitutoyo. The HLB shows its strengths only under the specified conditions. However, for those able to adhere to these parameters, it offers strong central performance—at a price significantly lower than that of the Mitutoyo.
Operational Limits and Recommended Sensor Formats
Both objectives were originally not designed for photographic use on full-frame sensors, but rather for industrial applications—typically with sensor sizes up to 2/3", and officially only up to 1/2" in the case of the Mitutoyo. This limitation is due to the calculated image circle, which in both cases is significantly smaller than the diagonal of a full-frame sensor. However, in practice, especially the Mitutoyo M Plan Apo 50x proves capable of delivering usable image quality well beyond this theoretical image circle.
When paired with a 200 mm tube lens, the Mitutoyo covers an image circle of about 30 mm in diameter with high and largely consistent sharpness. Even on a full-frame sensor (43 mm diagonal), the usable area remains impressively wide. Only at the outermost edges do minor compromises become visible in the form of subtle sharpness loss and occasional faint chromatic aberrations. These only appear under critical magnification and can be fully eliminated with a slight crop. For users who already plan for a small safety margin in composition or routinely crop in post-processing, this limitation will hardly be noticeable.
The HLB Plan Apo 50x behaves more sensitively in this regard: the area of high imaging performance is visibly smaller, and sharpness loss toward the edges is significantly more pronounced. For APS-C or MFT sensors, image quality is sufficient—these formats don't capture the critical outer image zones. On full-frame sensors, however, the HLB clearly reaches its limits. In the outer regions, noticeable blurring occurs, along with occasional local distortions and contrast degradation. Users wishing to employ the HLB on full-frame must either accept a visible drop in quality outside the center or crop the image accordingly. For typical centrally composed subjects, tightly framed stacking sequences, or image series meant to be combined, this isn’t a dealbreaker—but for large-format single-frame output, it becomes a real concern.
Summary
The Mitutoyo objective can be effectively used with large sensors, as long as the extreme image corners aren't overly relied upon. It thus offers a substantially larger optically usable image field. The HLB objective, on the other hand, is better suited for smaller sensors or intentionally center-focused framing. The choice of sensor format directly impacts how much of each lens’s potential is realized—and where the optical design begins to show its limits.
Conclusion
Both lenses deliver remarkable optical performance in their class—and each has strengths in different areas. The Mitutoyo M Plan Apo 50x impresses with its balance: it offers very high image quality across an unusually large usable image circle, displays consistent behavior across varying tube lens focal lengths, and is built with mechanical precision down to the finest detail. Sharpness is high, contrast is stable, and its optical performance remains predictable even under non-ideal conditions. For those working with large image fields, experimenting with different tube lengths, or looking to take full advantage of a full-frame sensor, the Mitutoyo is a reliably uncompromising choice—though its price, around €2800 new (as of 2025), certainly makes a statement.
The HLB Plan Apo 50x surprises with even higher brilliance in fine central detail, crisp microcontrast, and excellent performance within its ideal working range. When paired with a 200 mm tube lens and an APS-C or MFT sensor, it delivers image quality in the center that closely approaches that of the Mitutoyo—and at times even slightly exceeds it in terms of microcontrast and textural clarity—at a somewhat lower price point (here: €2300). It is also clear, however, that this lens is more tightly bound to its optimal operating conditions. Sharpness drops off more quickly toward the edges, tolerance to optical deviation—such as reduced tube length—is more limited, and its uniformity across the image field lags behind that of the Mitutoyo.
Choosing between the two is not a matter of right or wrong, but rather of application, budget, and personal priorities. The question posed at the beginning—whether the higher price or the cost savings pay off in practical photography—is, in my opinion, not decisive: those who rely on maximum image field correction, tightest mechanical tolerances, and versatile performance under varied setup conditions will not want to miss out on the extra performance the Mitutoyo offers. Those who work intentionally in a center-weighted style, with smaller sensors and stable conditions, and who place particular value on contrast and fine texture rendering, will find the HLB to be a serious tool—priced slightly below the Mitutoyo, yet with its own distinct optical character.
How do I decide for myself? When I want to capture a structure at the highest possible magnification and plan to crop the image all around from the outset, I reach for the HLB. In this case, central detail brilliance is what matters most—and that’s exactly where this lens excels. But when I want to capture a finely textured surface with repetitive patterns—like the scales on a butterfly wing—and need the entire image field at 50:1 to remain sharp edge-to-edge, then corner performance is critical. Even slight edge softness would be distracting, and cropping would sacrifice too much subject area. In such cases, I turn to the Mitutoyo. And I’m genuinely impressed by both lenses—each in its own way.
Butterfly wing scales of Chrysiridia rhipheus, captured with the Mitutoyo M Plan Apo 50x NA 0.55. This is a focus stack composed of 200 individual frames, with a magnified crop from the full image below. Each individual scale measures approximately 0.1 mm in width.
A direct comparison reveals: the Mitutoyo is the more versatile system, while the HLB is more specialized. Both lenses deliver more optically than their official image circle specifications would suggest. However, only one remains consistently sharp when image quality must be maintained across the full-frame sensor right to the corners. Those who require that will likely find the higher price of the Mitutoyo justified. Those who don’t can opt for the HLB as a worthwhile compromise—without any real sacrifice in the critical central imaging area.
Technical Specifications Mitutoyo m Plan Apo 50x NA 0,55
Magnification: 50x
Numerical Aperture (NA): 0.55
Optical Design: Infinity-corrected (requires tube lens)
Recommended Tube Lens Focal Length: 200 mm
Thread Diameter and Pitch: M26 x 36 TPI (x 0.706?)
Weight: 230 g
Housing Length: 66.2 mm
Housing Diameter: 30 mm
Parfocal Distance (Housing Length + Working Distance): 95 mm
Exit Pupil Diameter: approx. 6.0 mm
Focal Length: approx. 4.0 mm
Working Distance: 13.0 mm
Resolution: 0.34 µm
Depth of Field: 0.68 µm
Manufacturer-Recommended Sensor Size: up to 1/2"
Technical SpecificationsHLB Plan Apo 50x NA 0,55
Magnification: 50x
Numerical Aperture (NA): 0.55
Optical Design: Infinity-corrected (requires tube lens)
Recommended Tube Lens Focal Length: 200 mm
Thread Diameter and Pitch: M26 x 36 TPI (x 0.706?)
Weight: 325 g
Housing Length: 82 mm
Housing Diameter: 35 mm
Parfocal Distance: 95 mm
Exit Pupil Diameter: 5 mm
Focal Length: 4.0 mm
Working Distance: 13.0 mm
Resolution: 0.5 µm
Depth of Field: 0.9 µm
Recommended Sensor Size: Not specified by manufacturer
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