Rethinking 4/3 Depth Of Field

Started Apr 11, 2013 | Discussions thread
richarddd
Senior MemberPosts: 2,957Gear list
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Re: I'm not convinced...
In reply to Great Bustard, Apr 13, 2013

Great Bustard wrote:

Anders W wrote:

Great Bustard wrote:

Rriley wrote:

Ironically, I think shallow DOF with UWA is "da bomb":

24mm FF isnt UWA

I've always thought that 24mm (on FF) was the long end of UWA:

http://www.cambridgeincolour.com/tutorials/wide-angle-lenses.htm

The definition of ultra-wide is a little fuzzier, but most agree that this realm begins with focal lengths somewhere around 20-24 mm [on FF] and less.

If I'm in error on this point, I'd appreciate a link to a credible source with a "less fuzzy" definition.

I am not usually inclined to propose definite limits of anything, but 24 is to me precisely the border line between WA and UWA.

That's basically how I see it, too.  In fact, let me get nerdy (I know, I know -- too late!).  Let's think of focal lengths in terms of stops, with 0 stops being the sensor diagonal, and each stop increase/decrease doubles/halves the area of the scene on the focal plane.  Then, for FF, we have:

  • -4 stops --> 11mm
  • -3 2/3 stops --> 12mm
  • -3 1/3 stops --> 14mm
  • -3 stops --> 15mm
  • -2 2/3 stops --> 17mm
  • -2 1/3 stops --> 19mm
  • -2 stops --> 22mm
  • -1 2/3 stops --> 24mm
  • -1 1/3 stops --> 27mm
  • -1 stop --> 31mm
  • -2/3 stops --> 34mm
  • -1/3 stops --> 39mm
  • 0 stops --> 43mm
  • 1/3 stops --> 49mm
  • 2/3 stops --> 55mm
  • 1 stops --> 61mm
  • 1 1/3 stops --> 69mm
  • 1 2/3 stops --> 77mm
  • 2 stops --> 87mm
  • 2 1/3 stops --> 97mm
  • 2 2/3 stops --> 109mm
  • 3 stops --> 122mm
  • 3 1/3 stops --> 137mm
  • 3 2/3 stops --> 154mm
  • 4 stops --> 173mm
  • 4 1/3 stops --> 194mm
  • 4 2/3 stops --> 218mm
  • 5 stops --> 245mm
  • 5 1/3 stops --> 275mm
  • 5 2/3 stops --> 308mm
  • 6 stops --> 346mm
  • 6 1/3 stops --> 389mm
  • 6 2/3 stops --> 436mm
  • 7 stops --> 490mm
  • 7 1/3 stops --> 549mm
  • 7 2/3 stops --> 617mm
  • 8 stops --> 692mm
  • 8 1/3 stops --> 777mm
  • 8 2/3 stops --> 872mm
  • 9 stops --> 979mm

This thinking leads to the following classifications:

  • Wider than -2 stops:  UWA
  • Between -2 stops and 1 stop:  WA
  • Between -1 stop and 1 stop:  Normal
  • Between 1 stop and 2 stops:  Portrait
  • Between 2 stops and 3 stops:  Short Telephoto
  • Between 3 stops and 5 stops:  Long Telephoto
  • Longer than 5 stops:  Super Telephoto

Thus, 24mm would just miss UWA, and 22mm would be the border.

That seems correct, although I don't regard arguing definitions as the most productive of exercises.  Your mileage definitely varies.

I doubt anyone who has another view on whether 24mm is UWA will be persuaded by shifting the discussion to stops.

I'm sure this is exactly what Rriley meant. 

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