Proposing a simple shorthand for writing "35mm equivalent field of view"

Started Feb 6, 2013 | Discussions thread
Great Bustard Forum Pro • Posts: 41,751
But what they don't do...

Mike_PEAT wrote:

Olympus owners typically just use the word "equivalent" when it's needed...it's understood that "135/35mm format field of view" is understood.

...is apply the same crop factor to the f-ratio as they do the focal length.

example: 25mn (50mm equivalent).

Example:  25mm f/1.4 (50mm f/2.8 FF equivalent), where "equivalent" means :

  • The photos all have the same AOV (diagonal angle of view) and aperture (entrance pupil) diameter: 25mm / 1.4 = 50mm / 2.8 = 18mm.

  • The photos all have the same DOF (as well as diffraction softening) when they have same perspective (subject-camera distance), AOV, aperture diameter, and display size.

  • The photos all have the same motion blur and the same total amount of light falls on the sensor when the aperture diameter and shutter speed are the same (e.g. ISO 100 on mFT / ISO 400 on FF).

  • The photos all have the same same noise when the same total amount of light falls on the sensor if the sensors are equally efficient (less noise if the sensor is more efficient, more noise if the sensor is less efficient).

  • Other elements of IQ, such as resolution, bokeh, flare resistance, etc., as well as elements of operation, such as AF speed/accuracy, size, weight, etc., are not covered in this use of the term "equivalent".

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