A Comprehensive Guide to Choose the Right Lens
The lens is arguably the most critical component in any camera system, acting as the eye that gathers light and focuses the image onto the sensor. For embedded vision projects, particularly those utilizing high-quality camera modules like the Raspberry Pi HQ Camera, selecting the correct lens from Waveshare's diverse catalog is paramount to achieving the desired outcome. This guide will demystify the key lens specifications and provide a practical framework for making an informed choice.
Understanding the Core Lens Specifications
Choosing a lens involves balancing several key technical parameters that directly impact the final image and the camera's field of view.
1. Focal Length and Field of View (FoV)
Focal Length (EFL), measured in millimeters (mm), is the distance between the lens's optical center and the camera sensor when the subject is in sharp focus. It is the primary determinant of the Field of View (FoV), which is the extent of the scene captured by the camera.
- Short Focal Length (e.g., 2.7mm, 6mm): Results in a Wide-Angle view, capturing a larger area. This is ideal for surveillance, panoramic shots, or applications where the camera is close to the subject but needs to see a broad scene. Waveshare offers ultra-wide options like the 184° Ultra Wide Angle M12 Lens .
- Long Focal Length (e.g., 16mm, 25mm): Results in a Telephoto view, magnifying the subject and capturing a narrower area. This is essential for observing distant objects, detailed inspection, or achieving a shallow depth of field. Waveshare's 25mm Telephoto Lens is a prime example .
- Zoom Lenses (e.g., 8-50mm): Provide a variable focal length, offering flexibility to adjust the FoV without changing the lens. The 8-50mm Zoom Lens from Waveshare is a versatile choice for applications requiring dynamic framing .
2. Aperture (F-number)
The Aperture, expressed as an F-number (e.g., F1.2, F2.8), controls the amount of light passing through the lens to the sensor. It is a ratio of the lens's focal length to the diameter of the entrance pupil.
- Smaller F-number (e.g., F1.2): Indicates a larger aperture (or "faster" lens), allowing more light to reach the sensor. This is crucial for low-light conditions and for creating a shallow depth of field (bokeh effect).
- Larger F-number (e.g., F16): Indicates a smaller aperture, allowing less light but increasing the depth of field (more of the scene is in focus).
3. Sensor Size Compatibility
A lens must be designed to project an image circle large enough to cover the camera's sensor without causing vignetting (darkening at the edges). Waveshare's lens specifications often list the compatible sensor size (e.g., 1/2", 2/3", 1"). Using a lens designed for a smaller sensor on a larger sensor will result in vignetting.
Waveshare Lens Mount Types
Waveshare primarily supports three common industrial lens standards, each defining the physical connection between the lens and the camera body.
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Mount Type
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Flange Focal Distance
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Typical Use Case
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Waveshare Examples
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C-Mount
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17.526 mm
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High-quality, industrial, and telephoto lenses.
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16mm, 25mm, 35mm Telephoto Lenses
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CS-Mount
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12.526 mm
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Compact, wide-angle lenses. Requires a 5mm adapter ring for C-mount cameras.
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6mm Wide Angle Lens
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M12 Mount
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Variable (S-Mount)
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Compact, small-form-factor cameras (e.g., board cameras).
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184° Ultra Wide, 8mm Telephoto M12 Lenses
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Practical Selection Guide: Choosing Your Lens
The best lens depends entirely on your application's requirements. Consider the following scenarios:
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Application
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Key Requirement
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Recommended Lens Type
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Waveshare Example
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Wide-Area Surveillance
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Maximum FoV, good low-light performance.
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Wide-Angle, low F-number.
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6mm Wide Angle CS-Mount Lens (F1.2)
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Long-Distance Observation
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High magnification, narrow FoV.
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Telephoto (25mm or 35mm), high resolution.
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35mm Telephoto C-Mount Lens
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Variable/Flexible Scenes
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Adjustable FoV for different distances/subjects.
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Zoom Lens.
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8-50mm Zoom C-Mount Lens
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Compact/Embedded Systems
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Small form factor, high resolution in a small package.
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M12 Mount Lens.
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113° Small Distortion M12 Lens
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Waveshare Lens Showcase
Here are examples of Waveshare lenses that demonstrate the range of options available:
1. The Versatile Zoom
A zoom lens like the 8-50mm Zoom C-Mount Lens offers unparalleled flexibility, allowing you to quickly switch between a wide-angle view (8mm) and a powerful telephoto view (50mm).
2. The Long-Range Specialist
For capturing details from afar, a fixed telephoto lens such as the 16mm Telephoto C-Mount Lens provides a high-quality, consistent image with a narrow field of view.
3. The Compact Wide-Eye
For small, embedded projects, M12 lenses are the standard. The 113° Small Distortion M12 Lens provides a wide field of view with minimal image warping, making it excellent for close-range machine vision.
Conclusion
Choosing the right lens is a process of matching the lens's technical specifications—focal length, aperture, and mount type—to the specific needs of your application. By understanding these core concepts and exploring the robust selection of C-mount, CS-mount, and M12 lenses offered by Waveshare, you can ensure your embedded vision project captures the world with the clarity and perspective it requires.