Leitfaden zu Objektivanschlüssen: M12, C-Mount und CS-Mount für Bildverarbeitungskameras
M8, M12, C-mount, and CS-mount differ in thread, flange focal distance, and back focal length. This guide shows how to pick the right mount before you order hardware.
M12 (S-mount) uses an M12x0.5 thread with no fixed flange distance. Focus is set by threading the lens in or out and locking it. C-mount and CS-mount both use 1"-32 UN threads, but C-mount has a 17.526mm flange focal distance while CS-mount has 12.526mm. A lens can thread onto the wrong mount and still fail to focus.
The 5mm difference is the rule: a C-mount lens works on a CS camera with a 5mm spacer. The reverse usually does not work. Choose M12 for compact embedded systems, CS for compact cameras with standardized focus, and C-mount for larger sensors, adjustable iris, and maximum lens interchangeability.
Was ist der Unterschied zwischen M12-, C-Mount- und CS-Mount-Anschlüssen?
Two parameters define a lens mount: the thread interface, which is purely mechanical, and the registration distance, which sets where the image lands relative to the sensor. C-mount and CS-mount register at the flange, so the standard guarantees focus for any compliant lens and body. M8 and M12 register wherever the thread is locked, so the installer sets focus by hand. Commonlands manufactures lenses for all four, and S-mount, board lens, and M12 all name the same interface. The table compares them side by side.
| Parameter | M8 | M12 / S-Mount | CS-Anschluss | C-Mount |
|---|---|---|---|---|
| Thema | M8x0,35 oder M8x0,5 | M12x0,5 | 1"-32 UN | 1"-32 UN |
| Flanschbrennweite | Nicht standardisiert | Nicht standardisiert | 12,526 mm | 17,526 mm |
| Fokusmethode | Faden ein-/ausführen, arretieren | Faden ein-/ausführen, arretieren | Fokusring am Objektiv; standardisierte Flanschausrichtung | Fokusring am Objektiv; standardisierte Flanschausrichtung |
| Typischer Erfassungsbereich des Sensors | Bis zu 1/3" oder 1/2,7" | Bis zu 1/1,8" (bei ausgewählten Modellen 1/1,7"–1/1,6") | Bis zu 1" in kompakten Gehäusen | Bis zu 1" und darüber hinaus |
| Typischer Bildkreis | 4–7 mm | Bis zu 9 mm und darüber hinaus | Bis zu 16 mm | 16 mm und mehr |
| Iris-Steuerung | Behoben | Behoben (die meisten Modelle) | Fest oder manuell | Verstellbarer Ring – üblich |
| Systemgröße / Masse | So klein wie möglich, unter 1 g | Klein, typischerweise 2–15 g | Mittelgroß | Größter, schwerster |
| Typische Kosten | Niedrig | Kleinster Bereich pro Fähigkeit | Mittelklasse | Höchster |
| Am besten geeignet für | Endoskope, Lochkameras, Mikro-Drohnen | Embedded Vision, Robotik, Drohnen | Kompakte Industrie, ITS, Sicherheit | Bildverarbeitung, Prüfung |
Was ist M12 (S-Mount)?
M12, auch als S-Mount oder Board-Objektivanschluss bezeichnet, verfügt über ein metrisches M12x0,5-Gewinde, das direkt in eine Halterung an einem Kameramodul oder einer Leiterplatte eingeschraubt wird. M12-Objektive sind klein (in der Regel 10–25 mm lang), leicht (2–15 Gramm) und in Brennweiten vom Ultraweitwinkel-Fischaugenobjektiv bis zum Teleobjektiv erhältlich.
M12 has no standardized flange focal distance. Each design assumes a different back focal length, so focus is set during installation by threading the lens in or out against a live image, then locking it. That makes M12 flexible for embedded systems but not interchangeable the way C-mount and CS-mount lenses are. Optically it is a rigid assembly with no internal moving groups, and working distance runs from roughly 50mm to infinity uncorrected.
Was ist ein C-Mount?
C-mount uses the same 1"-32 UN thread as CS-mount but registers at a 17.526mm flange focal distance. The extra 5mm of back focus makes room for larger rear groups, an iris assembly, and coverage of larger sensors, commonly up to 1" and beyond. C-mount is the industrial machine vision standard, with the broadest ecosystem of interchangeable lenses across manufacturers.
Unlike M12, it focuses through an internal cam that rebalances aberrations across the focus range (Kingslake, Lens Design Fundamentals, 2nd ed.). Working distance is typically 100mm to infinity. The cam sets a hard minimum object distance (MOD), measured from the front of the lens to the object, inside which the image goes uniformly soft and an extension tube is required.
Many C-mount lenses add an adjustable iris for depth-of-field control, practical in machine vision because illumination is programmatically controlled. Use the depth of field calculator to quantify the effect. Select models are ruggedized for harsh environments, which applies to specific lenses, not the mount.
Was ist die Flanschbrennweite?
Die Flansch-Brennweite (FFD) ist der standardisierte Abstand zwischen der Referenzfläche des Objektivanschlusses und der Bildsensorebene, gemessen entlang der optischen Achse. Sie ist eine Eigenschaft des Objektivanschlusssystems und nicht eines einzelnen Objektivs. Die FFD des C-Mount beträgt 17,526 mm, die des CS-Mount 12,526 mm, während es für den M12-Anschluss keine einheitliche FFD gibt.
The standard works because both sides conform to the same number: a C-mount lens is designed so its focal plane sits 17.526mm from the flange at infinity, and a C-mount body is machined so the sensor sits at that same distance. Any compliant pair then focuses without adjustment. FFD is strictly mount geometry, not focal length or working distance.
The term appears in several forms across datasheets: flange back distance, register distance, and flange-to-film distance in the original photography usage. For focal-length and field-of-view math, use the EFL calculator.
Was versteht man unter der Backfokallänge in der Bildverarbeitung?
Back focal length (BFL) is the distance from the rear vertex of the lens, the last glass surface, to the image plane at infinity focus. It determines whether a lens can physically reach focus on a given camera: for a given sensor, effective focal length sets field of view while BFL sets mounting clearance. The distinction from FFD is exact. FFD is fixed by the mount standard and measured from the flange. BFL is a property of one lens, measured from the last glass vertex.
For M12 lenses, datasheets specify mechanical back focal length (MBFL): the distance from the thread seating surface to the sensor at infinity focus. Because M12 has no FFD, MBFL is how compatibility is specified, and it typically ranges from 2mm on wide-angle designs to 15mm or more on telephoto designs. The holder height must match it. Two lenses of the same effective focal length can have different MBFL, so verify it per lens. For how EFL drives framing, see how to choose focal length for machine vision.
On the bench, thread the lens fully in, then back it out slowly while watching a live image. If focus never comes, the holder height is wrong for that lens. Blurry at infinity but sharp up close means the holder is too tall, and soft corners that focus cannot fix point to off-axis aberrations or a chief ray angle mismatch.
Datasheets label this dimension inconsistently (MBFL, back focal distance, or BFL) and not every maker publishes it, so check the mechanical drawing before ordering holders. See the Commonlands M12 lens holder selection guide.
Kompatibilität von Objektivfassungen und Adapter
Thread fit does not guarantee optical compatibility. A lens can screw onto the wrong camera and still fail to focus, because the sensor sits at the wrong distance from the lens's designed focal plane. C-mount and CS-mount share the same thread, so a single 5mm precision spacer converts one direction. The other direction has no passive fix. The rules below cover the combinations engineers actually attempt.
C-Mount-Objektiv an einer CS-Mount-Kamera
Yes. Add a 5mm C-to-CS adapter ring to restore the 17.526mm registration the lens was designed for. Many CS-mount cameras ship with one. The C CS mount adapter does exactly this, and no thread adapter is needed, only the spacing ring.
CS-Mount-Objektiv an einer C-Mount-Kamera
Usually no. A CS lens expects the sensor 5mm closer than a C-mount camera provides, and the flange stops it at the correct thread engagement, so it cannot go further in. Without modifying the camera body, infinity focus is typically not achievable.
M12-Objektiv an einer Kamera mit C-Mount- oder CS-Mount-Anschluss
It is possible with an adapter, and the outcome is governed entirely by MBFL. The Commonlands CLA127 M12-to-C/CS adapter is 3.5mm thick and does not stack onto the flange distance: it recesses the M12 thread into the 1-inch throat so the lens seat ends up close to the sensor, at an effective depth of roughly 4mm. Wide-angle M12 lenses with an MBFL below about 4mm cannot reach infinity focus through it. The image plane forms short of the sensor, and no thread position moves it back far enough.
M12 lenses with an MBFL greater than about 4mm are the practical candidates: telephoto focal lengths such as 12mm, 18mm, 25mm, and 35mm sit far enough back to reach focus. The CLA127 M12 to C-mount adapter provides the mechanical interface. Some camera bodies also carry an IR-cut filter near the sensor, so verify both the back-focus budget and rear-element clearance past that filter for your lens before committing.
M8- vs. M12-Objektive: Für welches sollten Sie sich entscheiden?
M8 lenses use an 8mm thread (M8x0.35 or M8x0.5) and target extreme miniaturization. M12 lenses use a 12mm M12x0.5 thread and are the standard for embedded machine vision. The numbers are thread diameter, not focal length, and the larger M12 thread leaves more room for optical elements, which translates into image circle and correction headroom. If the system can physically accept M12, M12 is usually the safer default.
M8 lenses typically produce 4-7mm image circles and target 1/3" sensors, with 1/2.7" (about 6.7mm diagonal) as the practical upper limit. Many M12 lenses cover up to 1/1.8" (about 8.9mm diagonal), select models reach 1/1.7"-1/1.6", and resolution options extend to 20MP. Neither format has a standardized flange distance, so the holder-matching rules above apply to both. For matching image circle to sensor diagonal, see sensor size and lens compatibility.
Where M8 wins is package volume: the CIL857 6mm lens weighs 0.8 grams in its M8 variant and 2 grams in M12. In endoscope housings, pinhole enclosures, wearables, and micro UAV payloads with gram-level budgets, M12 hardware does not fit. Outside those cases, M12 offers a wider focal length range (0.8mm to 100mm across the Commonlands catalog), more sub-1% distortion options, and far deeper US sourcing.
The CLA812-AL (M8x0.35 to M12x0.5) and CLA811-AL (M8x0.5 to M12x0.5) adapters mount M8 lenses securely into M12 holders. The lens still has an M8 image circle and M8 optical limits. Use adapters for evaluation on M12 development boards. For production systems where M12 fits, use an M12 lens directly.
Die besten Objektive nach Anschlussart
The table ranks one primary lens per mount with a runner-up, all stocked in San Diego and shipping same day on orders placed before 12 PM PT.
| Montage | Objektiv | EFL | F# | Sensorabdeckung | Warum diese Wahl? |
|---|---|---|---|---|---|
| M12 / S-Mount | CIL250 25-mm-Teleobjektiv · 99 $ | 25 mm | F/2,0 | Bis zu 8 MP | Größte Reichweite, bei der das Objektiv noch in einen Board-Objektivhalter eingeschraubt werden kann; IR-korrigiert für den Einsatz bei Tag und Nacht |
| M12 / S-Mount | CIL350 35-mm-Teleobjektiv · 59 $ | 35 mm | F/2,4 | Bis zu 2/3", 8–10 MP | Zweitplatziertes M12-Teleobjektiv; deckt größere 2/3"-Sensoren zu einem günstigeren Preis ab |
| M8 / M12 | CIL857 6 mm · 39 $ | 6 mm | F/3.0 fixed | 1/2,7", 7,0 mm Bildkreis | Die kleinste und leichteste Variante (0,8 g in der M8-Ausführung) für Lochkamera-, Endoskop- und USB-Kameras |
| C-Mount | CIL531 8 mm · 149 $ | 8 mm | F/2,8–F/16 | Bis zu 2/3", 12 MP | Weites Sichtfeld mit einstellbarer Blende; ca. 58° HFOV bei einem 2/3"-Sensor |
| C-Mount | CIL579 75-mm-Teleobjektiv · 149 $ | 75 mm | F/3-F/20 | 8 MP | Zweitplatzierter C-Mount für großen Abstand; der große Blendenbereich eignet sich für ITS- und ANPR-Anwendungen im Außenbereich |
| CS-Anschluss | 8 mm CS-Mount · 59 $ | 8 mm | F/1,8 | Bis zu 1/1,7", 12 MP | Fast normal-to-wide view, about 50° HFOV on a 1/1.7" sensor, and it saves 5mm of body depth; Raspberry Pi HQ compatible |
Every entry is a lens Commonlands stocks and characterizes in-house, ranked by mount fit first, then by focal-length reach and aperture range.
Weighing suppliers as well as mounts? Our guide to Edmund Optics alternatives for imaging lenses maps seven vendors to the applications where each one fits, including where board-level M12 and C-mount lenses make more sense than catalog optics.
Häufig gestellte Fragen
Was ist der Unterschied zwischen M8- und M12-Objektiven?
M8-Objektive verfügen über ein 8-mm-Gewinde (M8x0,35 oder M8x0,5), während M12-Objektive ein 12-mm-M12x0,5-Gewinde verwenden. Das größere M12-Gehäuse ermöglicht den Einsatz größerer optischer Elemente, eine breitere Sensorabdeckung und mehr Gestaltungsfreiheit. M8 zielt auf extreme Miniaturisierung ab und deckt in der Regel Sensoren bis zu einer Größe von 1/3" oder 1/2,7" ab.
Kann ich ein C-Mount-Objektiv an einer CS-Mount-Kamera verwenden?
Ja. Setzen Sie einen 5-mm-Adapterring von C-Mount auf CS-Mount zwischen Objektiv und Kamera ein. Dadurch wird der Unterschied im Flanschabstand ausgeglichen und die korrekte Fokussierung auf unendlich wiederhergestellt.
Kann ich ein CS-Mount-Objektiv an einer C-Mount-Kamera verwenden?
In der Praxis ist dies in der Regel nicht der Fall. Bei einem CS-Objektiv wird davon ausgegangen, dass der Sensor 5 mm näher sitzt, als es bei einer C-Mount-Kamera der Fall ist. Ohne mechanische Anpassung ist eine Fokussierung auf unendlich in der Regel nicht möglich.
Wann sollte ich M12 statt C-Mount wählen?
Entscheiden Sie sich für M12, wenn Größe, Gewicht und Integration auf Leiterplattenebene eine Rolle spielen. M12-Objektive sind kleiner, leichter und kostengünstiger. Wählen Sie C-Mount, wenn Sie eine größere Sensorabdeckung, eine einstellbare Blende oder ein standardisiertes Wechselobjektivsystem benötigen.
Kann ich ein M12-Objektiv an eine Kamera mit CS-Anschluss anpassen?
Mechanically yes, with an adapter. Optically it depends on the lens MBFL and the adapter depth. Through the 3.5mm Commonlands CLA127 adapter the lens seat sits about 4mm from the sensor, so M12 lenses with an MBFL below about 4mm typically cannot reach focus. Telephoto focal lengths such as 12mm, 18mm, 25mm, and 35mm are the better candidates. Verify the focus range before committing.
Brauchst du Hilfe bei der Auswahl einer Halterung?
Commonlands fertigt M8-, M12-, C-Mount- und CS-Mount-Objektive für die industrielle Bildverarbeitung und Embedded-Vision-Anwendungen, wobei unsere Objektivkonstruktionen einer MTF-Charakterisierung unterzogen werden. Unser Ingenieurteam in San Diego kann gemeinsam mit Ihnen die FFD-, MBFL- und Adaptergeometrie abstimmen, bevor die Hardware bestellt wird.