Certainly what you state regarding DOF is true. I believe though the writer was not making a dogmatic absolute statement of scientific fact. He was generalizing.
>As the camera: subject/background ratio wasn't altered, DOF should be >SIMILAR for all four lenses. I'm pretty sure he knows that actual DOF is not changed by altering the subjects distance from the focal plane. That's only moving subjects in to, out of, or within the range referred to as DOF. I think he means that the *perceived* DOF will be *similar*, which is true for lenses close to the same focal length used at close to the same aperture. Not the same, but similar. Tom C. >From: >Reply-To: Pentax-Discuss Mail List <[email protected]> >To: "'Pentax-Discuss Mail List'" <[email protected]> >Subject: RE: M85mm f2.0 bokeh >Date: Sat, 28 Apr 2007 10:26:25 -0400 > >No,this assumption is wrong, DOF is >constant only for same fstop and >MAGIFICATION (in camera ). If he >used same camera position and fstop >and only changed lenses, the shorter >lenses will have same perspective >in the shots but with MORE Depth >of field than the longer lenses. >DOF is a function of magnification, >NOT the "subject/background" ratio. Mr. J. >> >-----Original Message----- >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of >William Robb >Sent: Saturday, April 28, 2007 9:10 AM >To: Pentax-Discuss Mail List >Subject: Re: M85mm f2.0 bokeh > > > >----- Original Message ----- >From: "Paul Stenquist" >Subject: Re: M85mm f2.0 bokeh > > > > Of course the 70 gives you more DOF. Thus, a bit crisper. > >I left the camera position static and cropped the 70mm and 77mm images >to be >similar to the 85mm images. >As the camera: subject/background ratio wasn't altered, DOF should be >similar for all four lenses. > >William Robb -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
