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Category: New Questions

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Photography Question 
Steve Beckle
BetterPhoto Member

member since: 2/3/2006
 

Depth of field markings on lenses


I've decided to enter the 21st century and replace my 25-year old Pentax SLR system. This question will seem stupid to anyone with newer equipment than mine, but so be it. On all my Pentax (manual focus) lenses, the depth of field is indicated using the distance scale (in feet/meters) that changes with focus, and a fixed f-stop scale. You know what I'm talking about, you bracket the distance scale between the f-stop markings on both sides of a zero-point, and that gives you the range of focus. Ok..I saw a picture of a Nikon AF 18-200 VR lens online and noticed that it has the depth of field distances markings in feet/meters. But unlike my ancient Pentax lenses, I don't see the fixed f-stop markings that delineate the depth of field for a given f-stop. Is this information somehow displayed in-camera somewhere? Or are you expected to use the depth of field preview button to determine the DOF.

3/13/2006 1:02:15 PM

 
Jon Close
BetterPhoto Member

member since: 5/18/2000
  Your manual focus Pentax lenses are usable on Pentax DSLRs, directly if they are K-mount, and with an adapter if they are M42 screw mount.

Depth of field scales are not very compatible with autofocus lenses. First, to speed AF, the amount of turning from close focus infinity is very short. This so compresses the DoF scale as to make it unreadable, though it is still included on many AF prime lenses. Secondly, it is not possible to incorporate the DoF scale with AF zooms the way it was done with manual focus push-pull zooms. Third, to trim costs many entry-level lenses eliminate both the focus distance and DoF scales.

DoF data is not displayed in any camera (yet). It is very subjective anyway, dependent on the final image size and viewing distance. Canon EOS cameras have a workaround called DEP or A-DEP mode. Of the 2, DEP is preferred. In this mode there is a 3 step process: (1) focus on the near subject you want included in the depth of field, (2) focus on the far subject, (3) press the shutter button the 3rd time and the camera automatically sets the appropriate aperture and focus distance and takes the picture. A-DEP is used on the lower-level models and is a one-step process that attempts to determine the near and far subjects covered by the focus sensors.

Otherwise, resort to depth of field preview (if your camera has it), or you can create useable DoF and hyperfocus tables with nifty freeware available at http://www.dofmaster.com/.

3/13/2006 1:40:18 PM

 
Christopher A. Walrath
BetterPhoto Member

member since: 4/25/2006
  Welcome to the 21st century. New and improved. So what if it's new if it's seldom improved.

5/9/2006 8:55:01 PM

 

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