Focal length 35mm equivalent, but not F-stop?

Started Jul 24, 2014 | Discussions thread
Great Bustard Forum Pro • Posts: 43,668
Equivalence is about format independent parameters.

edhannon wrote:

35mm equivalent focal length is a crutch invented to help us old f@*ts to transition from 35mm film to APS-C digital. It helped us transition from film by knowing what lens to use to get a particular FOV in APS-C using our experience from 35mm film..

However, like learning a second language, real proficiency only comes when you think in the new format.

Same applies to DoF - one needs to learn what DoF will result with the lens/f-stop/sensor size you have - not one that you are currently familiar with.

This transition is easier for those of us who used both 35mm and medium format film. I never did translate lens focal length or f/stop when I switched between my Pentax 35mm film camera and my 500C Hasselblad. I learned to think 35mm when I shot with the Pentax and 6x6 when I shot with the Hassey.

Equivalence does not require comparing to FF -- you can use the equivalence ratio (crop factor) between any two formats.  For example, the equivalence ratio between mFT and 1.6x is 1.25.

Of course, if you are not comparing formats, then there's no reason to be thinking of Equivalence.

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