Microscope field of view calculator
camera field = sensor dimension in pixels × pixel size / total magnification
Two deliberately distinct methods. From the sensor: pixel dimensions and pixel size give a rectangular field, the one the camera actually records. From the field number engraved on the eyepiece: the diameter of the circular field seen by eye. The tool reports width, height, diameter and area depending on the method, in the unit of your choice.
Total optical magnification: 20× · Pixels read out: 2048 × 2048 px
Scientific dossier
What the tool computes, what it assumes, where it stops being valid, and where its data comes from.
Method & formulascamera field = sensor dimension in pixels × pixel size / total magnification
camera field = sensor dimension in pixels × pixel size / total magnification
eyepiece diameter = field number / total magnification
The first describes a rectangle, the sensor area referred back to the specimen. The second describes a disk, the eyepiece field diaphragm referred back to the specimen. They never coincide: the camera records only a portion inscribed within the visual field.
- Field number
- · diameter in millimeters of the eyepiece field diaphragm, engraved on it. Typically 18 to 26 mm.
- Rectangular field
- · what the camera records: its proportions are those of the sensor, never a disk.
- Circular field
- · what the eye sees through the eyepiece: a disk whose diameter depends only on the field number and magnification.
- Effect of magnification
- · the field is inversely proportional to magnification: moving from 20× to 40× halves each dimension, hence quarters the observed area.
Validity domainThe calculation assumes the sensor is fully illuminated by the optical path.
The calculation assumes the sensor is fully illuminated by the optical path. An adapter of insufficient diameter, or a sensor larger than the available image field, produces vignetting: the usable field is then smaller than the computed value. No calibration is replaced here, for a measurement. Use a stage micrometer.
Binning does not change the fieldThis is the counter-intuitive point of the calculation.
This is the counter-intuitive point of the calculation. Grouping pixels 2×2 doubles the projected pixel size and halves the number of pixels read out, but the physical sensor area. Hence the portion of specimen imaged, is strictly unchanged. Confusing 'fewer pixels' with 'smaller field' is the classic mistake here.