Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
04-10-2008, 02:18 AM   #16
Veteran Member




Join Date: Sep 2006
Location: Virginia Beach VA USA
Photos: Gallery
Posts: 1,364
In addition to all the other arguments for f2.8 glass, assume for the moment you can shoot at f4.0. An f2.8 lens stopped down to f4.0 will return better and sharper images than an f4.0 lens wide open, everything else being equal.

04-10-2008, 02:35 AM   #17
Pentaxian
falconeye's Avatar

Join Date: Jan 2008
Location: Munich, Alps, Germany
Photos: Gallery
Posts: 6,862
QuoteOriginally posted by axl Quote
One thing that will stay always different is DOF. f4 will never be f2.8 ...
As i have written elsewhere, the hyperfocal distance H (multiplied by d/f to get the same magnification of a subject at hyperfocal distance) is:

H d/f ~= 1730 a

(f: focal length in mm, a: aperture in mm, d: sensor size in mm)


So, whatever be the lens and sensor, it is the mere diameter (in mm) which creates the DoF effect on a given subject (when moving forth and back to get the same print size of the subject -- and I do not say the same perspective ).

And tele lens have large apertures (in mm) anyway. My 75mm limit may be only 300mm f/4.0 but it would be 50mm f/0.67 for a normal length!!

So you tell me that you need less DoF than this? Cool!
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
f/4, iso, k-mount, k20, pentax lens, slr lens, sports, users
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Lens implications of high ISO bodies? Nass Photographic Technique 11 09-16-2010 01:47 PM
K-7 high ISO vs K20D high ISO supa007 Pentax DSLR Discussion 72 05-10-2010 04:24 PM
High iso jpgs GX20 (k20) 1600-6400 burnie Pentax DSLR Discussion 3 01-17-2010 12:39 PM
K20 high iso opinions!! COULDBE2 Pentax DSLR Discussion 4 07-03-2009 04:39 AM
High ISO quality of K20 lol101 Pentax News and Rumors 56 02-07-2008 03:44 PM



All times are GMT -7. The time now is 01:29 PM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top