14/03/2025
Lenses
The selection of these lenses complements Kurokesu cameras to ensure sharp, clear, and accurate imagery. Choose from a variety of lenses, including fixed and variable focus, wide-angle, and telephoto options, designed to meet the specific needs of your project. Whether you are developing a cutting edge robotic system or teaching the next generation of engineers, Kurokesu lenses provide the clarity and flexibility you need.
Common lens types and their uses
Lens types are usually the first thing people notice when choosing a camera lens, because they define how the scene will look before any deeper specifications are considered. Wide-angle lenses are used when more of the scene must fit into the frame, telephoto lenses help when the subject is far away, and fisheye lenses provide the widest coverage with obvious distortion. Low-distortion lenses are often preferred for machine vision, where geometry matters more than dramatic perspective. Varifocal lenses add flexibility during setup, while macro and telecentric lenses are used for close-up and precision inspection tasks. In practice, the right lens type depends on what needs to be seen, measured, or monitored.
| Lens type | Brief description | Typical use |
| Wide-angle | Short focal length, covers a larger scene. Good when you need overview rather than distant detail. Shorter focal lengths give a wider field of view. | CCTV room coverage, doorways, robotics, embedded vision, general-purpose board cameras |
| Varifocal / Zoom | Lets you adjust focal length to tune framing after installation. Very common when exact field of view is not known in advance. Axis describes varifocal options as flexible field-of-view solutions. | CCTV installation, test benches, prototypes, multi-purpose streaming/inspection setups |
| Telephoto | Longer focal length, narrower view, larger subject image. Used when the target is far away or small details matter. Basler notes that larger focal length increases telephoto characteristics. | License plates, perimeter monitoring, distant objects, close-up inspection from longer working distance |
| Low-distortion wide-angle | Wide field of view, but with straighter lines and less geometric warping than fisheye. Useful when you want wide coverage without strong barrel distortion. Edmund explicitly lists this as a common machine-vision lens category; Theia highlights wide coverage with reduced distortion. | Machine vision, warehouse monitoring, mobile robots, analytics where image geometry matters |
| Fisheye | Extremely wide field of view, often around 180° class, but with strong intentional distortion. Useful when one camera must see almost everything around it. Axis markets fisheye sensors for wide-area coverage and panoramic view. | Ceiling surveillance, room overview, in-vehicle view, compact systems, creative video angles |
| Standard / Normal | Balanced field of view, between wide and telephoto. Often the safest default when you want natural-looking perspective. | General CCTV, USB cameras, embedded cameras, basic inspection |
| Macro / Close-focus | Designed for short working distances and small objects. Prioritizes close-up detail over large scene coverage. Edmund lists macro imaging lenses among common imaging categories. | PCB inspection, tiny parts, lab work, product photography, barcode close-up work |
| Telecentric | Special measurement lens that keeps magnification much more constant with object distance and removes perspective error. This is not a general CCTV lens; it is a precision machine-vision tool. | Metrology, gauging, dimensional inspection, edge measurement, precision QA |
Key Lens Parameters
After lens type, the next step is understanding the parameters that actually decide whether a lens will work well in a real system. The lens mount determines mechanical compatibility with the camera, with M12 being common on compact embedded modules and C/CS being more typical for larger CCTV and industrial setups. Focal length defines how wide or narrow the captured scene will be, while aperture controls how much light reaches the sensor and also affects depth of field. Adjustable lenses may also offer focus, zoom, and iris controls, which can be useful during setup or when one camera must cover different tasks. Finally, the lens image circle must be large enough for the sensor. This is why legacy sensor format names such as 1/2.5" or 1/2.8" still matter even though they do not match the real sensor dimensions directly.
Lens mount
The lens mount defines the mechanical interface between the lens and the camera. In our case the most relevant options are M12 and C/CS mount. M12 lenses are compact, lightweight, and very common on embedded and board-level cameras. C and CS mounts are much larger and more flexible, with a wide ecosystem of industrial and CCTV lenses. The key difference between C-mount and CS-mount is flange distance: C-mount is 17.526mm, while CS-mount is 12.5mm, so a C-mount lens can usually be used on a CS camera with a 5mm adapter ring, but not the other way around.
Aperture / Iris
Aperture, usually written as f-number such as f/1.4 or f/2.8, controls how much light reaches the sensor. A lower f-number means a larger opening, so the lens collects more light, which is especially important in low-light CCTV and night imaging. Aperture also affects depth of field: a more open lens gives a shallower depth of field, while stopping it down increases the range that appears in focus. In practice, aperture is always a compromise between brightness, depth of field, and optical sharpness.
Focal length
Focal length is one of the most important lens parameters because it strongly affects field of view. A shorter focal length gives a wider view, while a longer focal length gives a narrower view and more magnified image. On a sensor such as Sony IMX290, which is a 1/2.8-inch format sensor with 6.46mm diagonal and 2.9µm pixels, a 2.8mm lens gives a very wide view, around 90° horizontal, a 4 mm lens is still wide at roughly 70° horizontal, a 6 mm lens is closer to 50°, and a 12 mm lens becomes much tighter at about 26° horizontal. These numbers are rough but useful for quick product selection.
Lens controls
Some lenses have adjustable controls and some do not. The most common are focus, zoom, and iris/aperture control. Focus adjusts the distance at which the image is sharp. Zoom changes focal length and therefore changes the field of view. Aperture control changes the amount of light entering the lens and also affects depth of field. Many compact M12 lenses are fixed-focus or manually focused, while larger C/CS lenses more often offer manual or locking controls for focus, zoom, and iris.
Image circle
The image circle is the size of the image projected by the lens onto the sensor plane. The lens must produce an image circle large enough to cover the sensor; otherwise dark corners or full vignetting will appear. This is where the old inch-type sensor notation becomes important. Sizes such as 1/2.5", 1/2.8", or 1/1.8" are legacy optical format names, not the real physical sensor size. They come from old video tube standards, so the quoted inch value is larger than the actual sensor diagonal. As a rough rule, the real sensor diagonal is about two-thirds of the stated optical format, which is why a 1" format sensor is roughly 16 mm diagonal, not 25.4 mm. That is also why choosing a lens by “inch rating” is really about matching the supported image circle to the sensor format.
