Sensor Size Comparison and Field of View (F.O.V)
This page explains the relationship between the area visible through the microscope eyepiece and the area captured by a DSLR, mirrorless camera or C-mount microscope camera. The captured field is not determined by sensor size alone. It also depends on the microscope optical path, the adapter optics and the usable image circle projected to the camera sensor.
Use this guide as a technical reference when comparing APS-C, full-frame, Four Thirds and C-mount cameras for microscope imaging. Final compatibility should always be checked with the actual microscope model, photo port and camera body.
DSLR and Mirrorless Camera Sensor Size Comparison
The illustration below compares typical camera sensor sizes used in DSLR and mirrorless cameras. These sizes help estimate the captured range, but they do not by themselves guarantee full image coverage.
About Image Sensor Sizes and Adapter Selection
Digital cameras use different image sensor formats. A larger sensor can potentially record a wider projected image area, but only when the microscope optical system and adapter provide a sufficiently large and well-corrected usable image circle. If the sensor is larger than the usable projected image area, vignetting or dark corners may appear.
1. Eyepiece View
The visual field is related to the eyepiece field number, such as 10X/22. The number 22 indicates a field number of 22 mm.
2. Sensor Size
The camera sensor records only the portion of the projected image that falls onto the sensor area. APS-C, full-frame and Four Thirds sensors therefore record different areas, even when the same microscope and adapter are used.
3. Adapter Optics
The adapter magnification and image circle determine how much of the microscope image can be used by the camera.
Sensor Size vs. Captured Range vs. Microscope Field of View
The illustration below summarizes how three factors interact: the eyepiece field of view, the camera sensor size and the adapter optics. In practical terms, the camera records the portion of the projected microscope image that falls on the usable sensor area.
- Eyepiece field number: The visual reference range, often shown as 10X/22 or similar.
- Projected image circle: The optical image delivered by the microscope and adapter.
- Camera sensor: The rectangular area that actually records the projected image. Image composition may also vary depending on the sensor aspect ratio or recording mode, such as 3:2, 4:3 or 16:9.
- Vignetting: Dark corners may appear if the sensor is larger than the usable image circle.
How to Read Eyepiece Field Number
- GSWH: Eyepiece model name or series.
- 10X: Eyepiece magnification.
- 22: Eyepiece field number, approximately φ22 mm.
- Common eyepiece field numbers vary by microscope and eyepiece type. Values around 18–22 are common in many compound microscope eyepieces, while some stereo microscope eyepieces may use wider field numbers such as 22–27.
Magnification and Calculation Method
The displayed size on a camera LCD or monitor is not the same as the optical magnification at the microscope. It is affected by the microscope objective magnification, adapter magnification, sensor size, display size, display scaling and viewing conditions.
= Objective magnification × Adapter magnification × (Display size ÷ Sensor size)
Calculation Example
| Camera | Canon EOS Rebel T3i |
| Sensor Size | Approx. 22.3 × 14.9 mm |
| LCD Monitor Size | 3.0 inch wide |
| Adapter | NY-1S, approx. 1.74× |
| Objective Lens | 20× |
| Approx. On-Screen Image Enlargement | 20 × 1.74 × (3 / 1.06) = approx. 98.5× |