Should crop factor be used when calculating camera field of view?
Asked 3/5/2015
3 views
2 answers
0
I’m calculating the field of view of smartphone cameras using:
FOV = 2 × arctan(sensor size / (2f))
where f is focal length and sensor size is the sensor width, height, or diagonal in mm.
Some camera specs also list a crop factor or a 35mm-equivalent (“effective”) focal length. When using this formula, should I use the actual focal length of the lens, or the effective focal length after applying crop factor?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
11y ago
2 Answers
4
You should use the actual focal length of the lens in question. When you include the sensor size into the equation FOV = 2 arctan(SensorSize/2f), you have already included the crop factor into your calculation.
That is because the so called crop factor is really nothing more than describing what field of view, in terms of a lens of a given focal length for a 35mm/FF sensor, will be given by a particular sized sensor. The reason a Canon APS-C sensor has a crop factor of 1.6x is because the linear dimensions of a Canon APS-C sensor are 1/1.6 the dimensions of a 36mm x 24mm full frame sensor. The same is true of a camera with a 2x crop factor: the 18mm x 12mm sensor has linear dimensions 1/2 that of a full frame sensor.
Originally by user15871. Source · Licensed CC BY-SA 4.0
user15871
11y ago
0
Generated from our catalog & community — verify before relying on it.
Use the actual focal length with the actual sensor dimension.
In the formula FOV = 2 × arctan(sensor size / (2f)), the sensor size already accounts for format differences, so you do not apply crop factor again. Crop factor is just a way to describe what focal length on a 35mm/full-frame camera would give the same field of view.
So:
- If you know the real focal length and the real sensor width/height/diagonal, use those directly.
- If a spec gives only the 35mm-equivalent focal length, first divide by the crop factor to recover the real focal length.
- Alternatively, if you use the equivalent focal length, then you must also use the 35mm full-frame sensor dimensions (36×24 mm, or its diagonal) in the formula.
In short: don’t mix real sensor size with equivalent focal length, or you’ll apply crop factor twice.
Recommended products
UniqueBot
AI11y ago
Your Answer
Related Questions
How do I calculate the Nexus 5 camera’s field of view correctly?
How do I calculate a smartphone camera’s angle of view and subject distance correctly?
Why is APS-C usually called 1.5× crop when the math gives about 1.53×?
Do quoted camera field-of-view specs include lens distortion?
Does image size on the sensor depend on sensor size or 35mm-equivalent focal length?