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Photography and other stuff.


Angle of View (AoV)

How wide or long is your lens ?  Many of us have used “Full Frame” (FF) 35mm SLRs long enough to know which focal length to select for the next shot.  A 24mm very wide lens for a streetscape, a 135mm medium telephoto for a portrait, a 500mm extreme telephoto for that stupid bird.  Now you have a digital SLR (dSLR) with a 1.5x or 1.6x crop factor (CF) sensor and your lens intuition isn’t as reliable as it once was.  What do you do ?  Well, I started to think in terms of Angle of View (AoV).  Not in terms of actual degrees, but more in terms of the width of the scene in front of me that I want to cover (or sometimes, the height of the scene).  After a while, I realized that I could use my hands and arms to span the view, and use my own body’s geometry to decide if the AoV is ultra wide, normal or whatever.  The specific camera that I’m using then lets me get from ‘whatever’ to a specific focal length.  This way of thinking has become even more important for my new adventure with Large Format (LF) photography, where a 90mm lens is “very wide” on a 4x5 camera.


By the way, “wide” is an angle of view expression, but “long” is a focal length expression: what gives?  Here are a few illustrations that I use to keep track of AoV, focal length and lens selection.  The AoV used in f.Zones is the diagonal AoV which is most commonly quoted in lens specifications.  The section on calculators has a spreadsheet for determining “equivalent focal length”, which uses both diagonal AoV and horizontal AoV (AOV.h).  In most cases, I prefer to use AoV.h.


            f.Zones a graphical way to compare lenses on FF 35mm and 1.6x CF SLRs

            crop factor a graphical comparison of FF 35mm and 1.6x CF images

            Full Frame AoV use your hands to estimate what focal length you need

            1.6x Crop Factor AoV use your hands to estimate what focal length you need


Thanks for looking, jim@jcolwell.ca


Last update: 2005-10-16



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