I realize that was your point. Just trying to clarify. In-focus and critically in focus are two different things. Paul On Nov 14, 2006, at 4:51 PM, J. C. O'Connell wrote:
> Your post concurs with mine as I have > previously stated the same thing, what > you are calling the point of critical > focus is what I am talking about all > along. > jco > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of > Paul Stenquist > Sent: Tuesday, November 14, 2006 4:08 PM > To: Pentax-Discuss Mail List > Subject: Re: Using a Super Tak w/ istDS- A challange to the list? > > > I think party of the confusion here is in regard to what constitutes > critical focus and what might fall within the depth of field of a > given lens. Every lens, no matter how wide has only one point of > critical focus. With my DA 12-24 at 12mm that point is nearly > impossible to find. Almost everything appears to be in focus. So one > could say that it's very easy to focus the 12mm lens. Yet there is a > point of critical focus. For important work, I try to locate that > critical point exactly where I want it. Sometimes I have to resort to > the distance scale to achieve critical focus with this wide a lens. > On the other hand, with my 400mm lens, it's easy to see what is in > focus and what is not due to the lack of depth of field. > On Nov 14, 2006, at 3:35 PM, J. C. O'Connell wrote: > >> I say its EASIER to focus longer lenses >> with the same accuracy at same fstop/speed, all >> else being equal. >> jco >> >> -----Original Message----- >> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On >> Behalf Of >> Cory Papenfuss >> Sent: Tuesday, November 14, 2006 2:46 PM >> To: Pentax-Discuss Mail List >> Subject: Re: Using a Super Tak w/ istDS- A challange to the list? >> >> >>> So, how does one measure ease of focusing in a lab? How does one >>> measure comparative ease of focusing (say a 35mm lens v a 105mm >>> lens)? >> >>> What tests are used, what equipment is used? How do you define >>> "ease?" Is the lens tested on a camera, or is the camera something >>> that gets in the way of an objective test? Is there an "easy of >>> focusing" machine to which the lens is attached? Do you use more >>> than >> >>> one sample of each lens? Do you change the light at times, vary the >>> subject? Is there an "ease of focusing" test target? How does the >>> target relate to real world subjects? For example, does the lab >>> target have a face? A nose? Eyes? Wear glasses? Or is it some >>> flat >> >>> sheet of paper with grid lines on it? >>> >>> Shel >>> >>> >> Again... I believe I was careful not to say, "ease," but rather >> "accuracy." The latter can be objectively measured and quantified >> and >> the >> former will always be run through an individuals' personal >> preferences. >> >> -Cory >> >> -- >> >> ********************************************************************* >> * > >> ** >> * >> * Cory Papenfuss, Ph.D., PPSEL-IA >> * >> * Electrical Engineering >> * >> * Virginia Polytechnic Institute and State University >> * >> ********************************************************************* >> * > >> ** >> * >> >> >> -- >> PDML Pentax-Discuss Mail List >> PDML@pdml.net >> http://pdml.net/mailman/listinfo/pdml_pdml.net >> >> >> -- >> PDML Pentax-Discuss Mail List >> PDML@pdml.net >> http://pdml.net/mailman/listinfo/pdml_pdml.net > > > -- > PDML Pentax-Discuss Mail List > PDML@pdml.net > http://pdml.net/mailman/listinfo/pdml_pdml.net > > > -- > PDML Pentax-Discuss Mail List > PDML@pdml.net > http://pdml.net/mailman/listinfo/pdml_pdml.net -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
