Lens Calculator

The tool helps you find the right lenses and the necessary accessories for your optical system. To start the calculation, please fill in the input fields as precisely as possible. The calculator strictly follows predefined parameters. This means that even slight variations – as little as 0.1 mm – can lead to potentially suitable lenses being excluded from the results.

 

• Input Your Parameters: Specify your sensor, object width/height, working distance, and/or desired magnification.
• Select Mount & Filter: Define your camera mount and any optical filters you intend to use.
• Calculate Solutions: The system instantly computes and displays a list of compatible Schneider-Kreuznach lenses.
• Detailed Accessory Chains: For each lens solution, view the precise accessory chain required, including extension tubes, adapters, and Unifoc systems.
• Explore & Export: Compare solutions, view technical drawings, download datasheets and STEP files, and save your complete calculation as a PDF.

• Sensor: Select your camera sensor from the list (standard formats, specific manufacturer models, or enter a custom size).
• Working Distance (WD): Ensure the dropdown is set to "WD" and enter your desired working distance in millimeters. This is the distance from the front edge of the lens to the object.
• Object Width / Height: Define the dimensions of the area you want to capture. One value is sufficient.

Based on this input, the calculator determines the required magnification and searches for suitable lenses. This mode is ideal if you have a fixed working distance and need to achieve a specific field of view.

• Sensor: Select your camera sensor.
• Working Distance (WD): Enter the desired working distance (set dropdown to "WD"). You may also leave this field blank, which will provide a larger list of possible lenses.
• Magnification: Enter the desired optical magnification. The object width and height fields will be deactivated, as they are implied by the magnification.

This mode is useful when magnification is a key requirement for your application and the working distance is also important.

• Sensor: Select your camera sensor.
• Focal Length (FL): Change the dropdown next to the working distance field from "WD" to "Focal length", and enter the desired focal length of the lens.
• Object Width / Height or Magnification: Complete your input either by specifying your object’s dimensions or by directly entering the required magnification.

This mode is especially useful if you already have a specific focal length in mind or want to work with specific lens types and determine the resulting working distance.

• Camera Mount: Choose your camera’s mount type (e.g., C-Mount, F-Mount). For many common mounts, the flange distance (distance from the camera’s mounting flange to the sensor) is automatically filled into the "Camera Flange (mm)" field and set to read-only.
• Custom Mounts: If your mount does not have a predefined flange distance (e.g., M42x1), please enter the flange distance manually.
• Optical Filters: If you wish to use an optical filter (e.g., bandpass), select it from the list. The calculator will include it in the accessory setup and recommend the appropriate filter size.

After entering all relevant parameters, click "Calculate system".

• Results Table: The calculator will display a list of potentially suitable lenses. Key parameters such as effective focal length, resulting magnification, required extension rings, effective working distance, flange focal distance, object-to-image distance, and object-to-camera distance are clearly shown.
• Accessory Chain: Click on the name of a lens (indicated by a "+" symbol) to view the detailed accessory chain for the selected optical setup. This expanded view shows all components in sequence, from the (optional) filter to the lens, any extension rings or adapters, and the camera mount.
• UNIFOC Options (if available): For lenses requiring a UNIFOC focusing helicoid (e.g., PYRITE series), a dropdown will appear here. You can choose between different UNIFOC types, which affect focus range and total system length. The table and accessory chain update accordingly.
  
  

Angle of View
Also referred to as the opening angle, this describes the angular extent of a given scene that is imaged by the lens. In our calculator, it is often split into horizontal (h) and vertical (v) values, depending on the aspect ratio of the selected sensor. A wider angle of view captures more of the scene, while a narrower angle provides a "telephoto" effect.

Aperture / F-Stop (F/#)
Also known as the iris or diaphragm, this is the adjustable opening inside the lens that regulates how much light reaches the sensor. A wider aperture (lower f-number) lets in more light but may introduce optical aberrations. A narrower aperture (higher f-number) reduces light but often increases depth of field and sharpness. However, stopping down too far (beyond the recommended maximum, Fₘₐₓ/#) causes diffraction, which degrades image quality. Standard f-stops include: f/1.4, f/2.0, f/2.8, f/4.0, f/5.6, f/8, f/11, f/16, and f/22. Moving from one standard f-stop to the next halves the transmitted light intensity.

Circle of Confusion (CoC)
The maximum acceptable diameter of a blur spot on the image plane (measured in mm or pixels) that is still perceived as sharp. It is the core metric for determining depth of field. As a general guideline, use a CoC of roughly 2 pixels for monochrome sensors and 4 pixels for color sensors with a Bayer pattern.

Depth of Field (DoF)
The distance range on the object side, in front and behind the optimal focus pointwhere the subject appears acceptably sharp (blur is ≤ CoC). DoF increases as you close the aperture (higher f-stop) and decreases dramatically as magnification increases (DoF ~ F/# / β²). To achieve a deeper DoF, you must either stop down the aperture or reduce the magnification.

Depth of Focus
The tolerance range on the image side (at the sensor plane) within which the image maintains acceptable sharpness. It should not be confused with Depth of Field, which applies to the object being imaged.

Extension Tube
A physical adapter placed between the lens and the camera mount to increase the distance between the lens and the sensor. Spacers are necessary when the required Free Working Distance (FWD) is shorter than the lens’s mechanical Minimum Object Distance (MOD).

Field of View (FoV)
The actual physical dimensions (horizontal, vertical, and/or diagonal) of the object area that is captured by the active sensor at a specific working distance.

Flange Focal Distance (FFD)
The precise distance (in mm) from the mechanical mounting flange of the camera or lens to the image sensor. For a system to focus properly, the FFD of the lens and camera must match. Standardized FFDs include C-Mount and TFL-Mount (17.526 mm), and F-Mount (46.5 mm). Other thread mounts (like S/M12, M42, M58, etc.) do not have a universal standard, so the correct FFD must be verified via the manufacturer's data sheets.

Focal Length (f)
A fundamental characteristic of an entocentric lens. In optical physics, it is the distance from the secondary principal plane H‘to the focal point when light rays are collimated. Common focal lengths include 4.8, 6.5, 8, 12, 16, 25, 35, 50, 75, and 100 mm. For a given Field of View, a longer focal length requires a greater working distance and results in a narrower opening angle (2·ω).

Focusing Unit / Helical Mount (e.g., UNIFOC)
A mechanical focusing mechanism placed between the lens and the camera. Many industrial lenses do not have built-in focus rings. Instead, they rely on external helical mounts (like a UNIFOC system) that provide a precise, adjustable extension range (e.g., 0 - 12 mm for the UNIFOC 12). This allows you to fine-tune the exact focus distance for your specific application.

Image Circle
The circular area of light that a lens projects onto the image plane. For an image to be properly illuminated from edge to edge, the diameter of the lens's image circle must be equal to or larger than the diagonal measurement of the camera sensor. If the sensor is larger than the maximum supported image circle, the corners of the image will appear dark (a phenomenon known as vignetting).

Magnification (ß‘)
The ratio of the image size projected onto the sensor to the actual physical size of the object. Ideally, magnification remains identical across the horizontal, vertical, and diagonal axes. Entocentric lenses are usually optimized for specific magnifications or ranges. Magnification heavily impacts the Depth of Field: DoF ~ 1/β².

Modulation Transfer Function (MTF)
A metric used to evaluate the optical resolution and contrast performance of a lens. MTF describes how well subject contrast is transferred to the sensor across various spatial frequencies (measured in line pairs per mm, lp/mm). A practical target is a MTF value of about 30% at two-thirds of the Nyquist frequency of the sensor. The Nyquist frequency in lp/mm is calculated by 1000 / (2 x pixel size in µm)

Object-Image Distance [OO′]
The total physical distance from the object being focused on to the camera's sensor. For any specific camera and lens combination, this overall distance reaches its minimum at a 1:1 magnification (β = 1), where [OO′] = 4·f + [HH′].

Working Distance
The distance from the object to the first mechanical part of the lens, typically the lens barrel. For lenses with a protruding front lens element the value refers to the lens vertex of this first element.

Object Size (Object Width / Height)
The physical dimensions of the target area you need to inspect. Together, the object width and height define the required Field of View (FoV) at the focal plane. Entering these dimensions into the lens calculator helps determine the necessary sensor size, focal length, and magnification.

Principal Planes (H, H′)
The theoretical Primary (H) and secondary (H′) planes of a lens. Combined with the focal length (f), they dictate how the lens projects an image of an object located at a given object distance. The gap between these planes [HH′] can be positive or negative depending on the lens design. The exact positions of H and H′ are factored into our calculator for maximum accuracy.

Resolution
In industrial optics, this term is used in two ways:

1. Lateral/Physical Resolution: The actual object-side dimension captured by a single sensor pixel (measured in µm/pixel).
2. Optical Resolution: The ability of the lens to sharply resolve details, often quantified via MTF (lp/mm) to match a specific minimal pixel size.

Sensor
The electronic component that serves as the image plane in a vision system. It is defined by its physical size, its horizontal/vertical pixel count, and the size of the individual pixels (currently, our tools assume square pixels). To prevent corner darkening (vignetting), the diagonal measurement of the sensor must be smaller than the maximum image circle supported by your chosen lens.

Wavelength (λ)
A core property of light that determines its color and photon energy, typically measured in nanometers (nm) or micrometers (µm). For baseline calculations (such as Airy disc diameter and max recommended F-stop), a standard visible wavelength of λ = 550 nm is used. Common spectral bands in machine vision include: UV (< 400 nm), Visible (400–700 nm), Blue (400–490 nm), Green (490–590 nm), Red (590–700 nm), Near-Infrared / NIR (700–1000 nm), Short-Wave Infrared / SWIR (700–1700 nm).

This glossary was created with the kind support of STEMMER IMAGING. Thank you very much.