Apertia · Library
Calculate · Geometric blur diameter (mm)
A thin-lens plan using distances from the sensor plane. Real lens behaviour, focus breathing and computational photography are outside this model.
Compare a geometric blur diameter
Enter the sensor preset, actual focal length, f-number, focus distance and background distance from the sensor plane. The native geometry estimates the out-of-focus blur diameter and a framing-related comparison.
A blur diameter describes this geometric model. It does not predict the appearance of a particular lens’s aperture highlights, aberrations or bokeh, and it does not simulate a phone’s computational portrait processing.
Change one assumption at a time
Compare the same subject geometry while varying aperture, focal length or background distance. Read the units and model interpretation alongside the number; a larger numeric diameter is not by itself a judgement of image quality.
Method and reference context
A thin-lens plan using distances from the sensor plane. Real lens behaviour, focus breathing and computational photography are outside this model.
Results
Example calculation
Geometric blur diameter (mm): worked out from the values already filled in the form above.
Inputs
- Sensor: Full frame
- Focal length: 50
- Aperture: 8
- Focus distance: 2,000
- Background distance from sensor (mm): 15,000
Result
- Geometric blur diameter (mm): 0.143132383
- Blur diameter / portrait frame width: 0.0059638493
- Meaning and limits: Geometric blur, not a lens bokeh-quality rating
Related tools
Horizontal angle of view (°) · Airy-disk diameter (mm) · Focus-stack plan