Lens Spotlight
HLB M Planapo 10x
The HLB Plan Apo 10x is a microscope objective designed for metallurgical applications. This test aims to evaluate how well it performs in focus stacking setups without the use of a professional microscope.
The Objektive
The HLB Plan Apo 10x is a lens designed specifically for metallurgical applications. It is part of a series of objectives with varying magnification levels, all of which are parfocal—meaning they share the same total length in terms of housing and working distance. The housing diameter is also largely consistent across the series, which posed a particular design challenge for the lower 2x magnification lens, especially in the front element region. However, the primary advantage of this parfocal design emerges when used with specialized microscopes, where the camera mount is mechanically fixed to suit all lenses, often with an integrated tube lens.
A large working distance is essential for many metallurgical applications, especially because the illumination typically comes from the side. This marks a significant difference from most microscope objectives developed for laboratory use (e.g., in medicine, biology, etc.), where transmitted light is the norm and a long working distance is unnecessary—or even problematic.
While the HLB Plan Apo 10x was originally designed for use on specialized microscopes, its long working distance makes it ideally suited for use in focus stacking setups, where it can be mounted to a full-frame camera with the appropriate tube lens. The generous working distance greatly simplifies lighting the subject, offering excellent practicality for high-magnification imaging.
The HLB Plan Apo 10x is part of a parfocal objective series with an identical housing diameter.
The Manufacturer
The manufacturer is the Japanese company Shibuya Optical, which produces objectives for a wide range of professional fields, as well as specialized microscopes, accessories, and various other optical instruments. In Europe, the lenses are imported by Rainer Ernst Feinwerktechnik (www.stonemaster.eu).
The design was likely inspired by a series of objectives from the Japanese company Mitutoyo, which are also parfocal and set industry standards with their long working distances and exceptionally high imaging quality—albeit at very high prices. The HLB objective series represents a group of competitive alternatives with similar characteristics, and some of these lenses, such as the HLB Plan Apo 20x, offer optical quality that approaches that of Mitutoyo—though at a similarly high price point. However, the HLB lineup also includes significantly more affordable models that cost roughly half as much as a Mitutoyo M Plan Apo.
Numerous Mitutoyo clones from China are also available. While they often closely resemble the Japanese originals in appearance and are far less expensive, one should not assume their optical performance is comparable just because they look similar.
The lens featured here was provided for testing by Rainer Ernst Feinwerktechnik (manufacturer of the Stonemaster products).
Technical Specifications
Magnification: 10x
Numerical Aperture: 0.28
Infinity-corrected (requires tube lens)
Compatible tube lens focal length: 200 mm
Thread diameter and pitch: M26 x 0.706
Weight: 190 g
Housing length: 61 mm
Housing diameter: 34 mm
Parfocal distance (housing length plus working distance): 95 mm
Focal length: 20 mm
Working distance: 34 mm
Resolution: 0.98 µm
Depth of field: 3.5 µm
Imaging Performance – 208 mm Tube Lens
The following test images illustrate the optical performance of the lens. The first shows an overview image (full-frame sensor) taken with the Raynox DCR 150 tube lens, resulting in an approximate nominal magnification of 10x. The two subsequent images each show a magnified crop.
Test image at nominal magnification (DCR 150), with frame markers indicating the subsequent cropped enlargements – reasonably good sharpness, no visible vignetting, free from chromatic aberrations, and distortion at the edges is barely noticeable.
In the central cropped enlargement, good and consistent detail sharpness, free from chromatic aberrations or distortion.
In the corner crop enlargement, the decrease in detail sharpness is clearly noticeable, with structures appearing softer. A slight pincushion distortion is also visible in the corners.
The test image of the HLB Plan Apo 10x (NA 0.28), captured with an almost ideal tube lens focal length of 208 mm, demonstrates an overall very convincing optical performance on a full-frame sensor.
Center
In the center, the lens delivers excellent detail reproduction: fine conductor paths, tight structures, and microscopically small elements of the test pattern appear clearly separated, with high sharpness and very good microcontrast. The resolution appears well-defined, and the brightness distribution is balanced, with no significant blooming or contrast loss.
Extended Center
In the extended center area, this level of quality is largely maintained. The rendering remains fine and dimensional, with only minimal contrast degradation—barely noticeable in practical use. Structures retain their definition, and there are no distracting color errors or aberrations.
Edge Zone
In the edge zone, a gentle drop in performance is noticeable. Lines become slightly softer, microcontrast diminishes, and a subtle compression of fine details begins to appear. Still, the image remains very usable—especially when compared to many other objectives in this magnification range on full-frame sensors. There is no abrupt loss of sharpness, but rather a gradual transition, which indicates very good optical correction.
Overall Impression
When used with the proper optical configuration, the HLB Plan Apo 10x delivers high-end image quality—with outstanding sharpness in the center, solid performance in the extended center, and a well-controlled, relatively mild drop-off at the edges. For full-frame focus stacking applications, it is a highly capable tool that performs on a level comparable to more expensive competitors like Mitutoyo. The high numerical aperture of 0.28 is clearly reflected in its fine resolution and balanced contrast rendition.
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 6.25x (instead of 10x). Some metallurgical microscope objectives from the HLB series tolerate this setup to a certain extent—though not all equally—and this test is intended to reveal what kind of qualitative compromises can be expected when using the Mitutoyo M Plan Apo 10x under these conditions.
Test image with DCR 250: The shorter tube lens focal length results in a reduced magnification. With this combination (which the lens was not designed for!), the pincushion distortion is significantly more pronounced than at the nominal magnification.
In the central cropped enlargement, detail sharpness decreases slightly from the center toward the edge.
In the corner cropped enlargement, distortion and blurring increase dramatically toward the edge, making approximately one-third of the total image area near the periphery likely unusable.
The test image shows the performance of the HLB Plan Apo 10x (NA 0.28) under a suboptimal configuration: it was operated with a 125 mm tube lens, although the objective is designed for 200 mm—resulting in a noticeable impact on image quality, especially when used with a full-frame sensor.
Center
In the center, the imaging performance remains at a good level despite the altered setup. The fine conductor structures of the test object are still well separated, and the line definition is differentiated, although visibly softer than with the optimal focal length. Microcontrast is reduced, grayscale gradients appear slightly flattened, and the crisp rendering seen with a 200 mm tube lens is lacking.
Extended Center
In the extended center, these effects become more pronounced. Individual structures begin to blur together, and initial signs of spherical aberration become evident—small areas lose precision in definition. Fine edges also appear generally softer, likely due to the reduced effective numerical aperture resulting from the lowered magnification.
Edge Zone
In the edge zone, the loss in quality is significant. The image is visibly soft, with a notable drop in contrast. Details are still visible but often blurry or affected by localized brightness loss. Especially along the right edge, the image appears optically compressed and slightly distorted—possibly a result of field curvature combined with the altered optical path.
Overall Impression
Using the HLB Plan Apo 10x with only a 125 mm tube lens is not recommended from an optical standpoint—at least not with a full-frame sensor. Central sharpness remains usable, but in the extended center and particularly at the edges, the lens is clearly pushed beyond its limits. The root cause lies in the reduced magnification and its consequences: lower effective aperture, altered chief ray angles, and increased field curvature. For users who depend on image uniformity and fine detail rendering, a 200 mm tube lens is clearly the preferable choice.
Comparison HLB M Plan Apo 10x – Mitutoyo M Plan Apo 10x
The direct comparison with the Mitutoyo M Plan Apo 10x shows that the HLB M Plan Apo 10x is only slightly inferior to this extremely high-quality and sharp-rendering objective—at least when used with a tube lens focal length of around 200 mm.
The HLB M Plan Apo 10x demonstrates its capabilities in comparison with the Mitutoyo M Plan Apo 10x, and both lenses are shown side by side in the direct comparison below.
In the direct comparison between the HLB M Plan Apo 10x (left) and the Mitutoyo M Plan Apo 10x (right), clear—though not dramatic—differences in imaging performance become apparent, particularly in microcontrast, detail separation, and visual uniformity on a full-frame sensor.
The HLB lens delivers a clean and consistent image in the center and extended center zones. Line clarity remains stable, and fine structures are reasonably well differentiated. However, the image appears slightly softer overall: microcontrast is reduced, especially in densely patterned areas, giving the image a flatter, less crisp appearance. Edge performance remains usable, though precision drops off slightly. No significant field curvature is visible.
The Mitutoyo, on the other hand, provides noticeably higher precision in nearly all aspects. Fine structures are more clearly resolved, dark areas appear deeper, and transitions between light and dark are more sharply defined. Image consistency is also more uniform across the entire field. In challenging zones—such as areas with high line density or low-contrast elements—the superiority of the Mitutoyo is evident.
Impression
The HLB M Plan Apo 10x delivers solid optical performance and represents a compelling option for high-resolution macro imaging on full-frame sensors—especially when considering the price-to-performance ratio. However, in a direct comparison, the Mitutoyo M Plan Apo 10x remains visibly superior: more contrast-rich, more precise, and more uniform across the image field. For applications demanding maximum microcontrast and fine detail resolution, Mitutoyo is the top choice. Nonetheless, the HLB remains a serious alternative—particularly for ambitious work on a more limited budget.
Imaging Performance – 208 mm Tube Lens: Microprocessor
A tiny microprocessor originally intended for mobile phone electronics contains extremely delicate structures. Measuring just 3 × 3 mm in size, it serves as a subject that demonstrates not only a lens’s sharpness and detail resolution but also its color reproduction capabilities.
The test with the microprocessor demonstrates relatively good sharpness and color reproduction, and the cropped section—approximately one millimeter wide (below)—reveals the image quality in greater detail.
The overview image (first picture) clearly demonstrates how well the lens can evenly and sharply render a larger structural area—on a full-frame sensor, no less. The outer bond pads and the complex internal structures remain clearly distinguishable. Notably, even in this wide shot, there are no significant edge distortions or visible field curvature, which speaks to the lens’s excellent correction—especially regarding the flatness of the focal plane, which is essential for microphotography.
The second image, a cropped enlargement from the red-marked area, reveals the full potential of the lens in detail. The rendering is largely uniformly sharp, the circuit traces are distinctly separated, and the high structural density is resolved with good differentiation. There are no color fringing artifacts or excessive contrast loss, although the overall contrast appears slightly subdued. Particularly striking is the consistent reproduction of the complex transitions between highly detailed and more uniform image areas—an indication of good control over field curvature, astigmatism, and chromatic aberration.
Compared to earlier test images of other lenses in this series, the 10x stands out as one of the most capable within the HLB Plan Apo lineup. It effectively utilizes its numerical aperture of 0.28 without visibly pushing the limits of its design. Even at this magnification, the depth of field remains shallow but well centered and free from disruptive blur zones.
In summary, these two images paint a very positive picture: the HLB Plan Apo 10x is excellent for high-resolution microphotography of technical structures, especially flat objects such as semiconductor chips. The combination of high resolution, balanced contrast, and a flat focal plane makes this lens a powerful tool for demanding applications in focus stacking and microphotography.
Resolution Test
The Zeiss Resolution Test 300 allows the resolution of a microscope objective to be read as a numerical value. While this reading involves some degree of interpretation and is not entirely precise (see details here), it does provide a useful general impression of fine detail and image rendering quality.
The resolution value, shown here in the two right fields, was measured at the center of the lens at 560 line pairs per millimeter (lp/mm).
Conclusion
The HLB M Plan Apo 10x is a powerful industrial objective lens well-suited for high-resolution macro photography on full-frame sensors—especially when the tube lens focal length is optimally matched to the recommended setup (200 mm). In the center and extended center areas, it delivers a clean, uniform image with well-resolved structures and largely neutral color reproduction. Line rendering is precise, and even in densely structured areas, the image remains clear, though with slightly reduced microcontrast compared to top-tier models.
Performance in the edge zone drops off somewhat but remains at a usable level—without distracting chromatic aberrations or significant field curvature. Particularly noteworthy is its low susceptibility to color fringing and its overall consistent resolution performance.
In direct comparison to the Mitutoyo M Plan Apo 10x, the HLB lens is only marginally behind. The Mitutoyo appears sharper, higher in contrast, and more uniform across the entire image field—especially when imaging very fine structures or challenging contrast conditions. Those seeking maximum precision and absolute perfection will appreciate the finer differentiation of the Mitutoyo.
Nonetheless, the HLB remains a convincing alternative: it offers very good optical performance, high mechanical build quality, and a design tailored for professional applications—all at a significantly lower price. For those working in demanding macro photography but not absolutely reliant on the last reserves of microcontrast, the HLB M Plan Apo 10x is an excellently suited lens with a very attractive price-to-performance ratio.
Advantages
Extremely long working distance, high image sharpness and detail accuracy, parfocality within the objective series allowing for easy lens changes, and a significant price advantage compared to the Mitutoyo reference objective.
Disadvantages
Unusual thread size requiring a special adapter (e.g., www.stonemaster-onlineshop.de); significant loss of image quality when using 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