[rollei_list] Re: DOF (was Re: Rolleiflex 35mm Cameras)
- From: CarlosMFreaza <cmfreaza@xxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Fri, 13 Nov 2009 12:34:45 -0300
And it is not _purely_ a function of aperture, if you think DOF as
percentage, this is a statement from one of the website you quoted:
"..depth of field, expressed as a percentage of the distance to the
subject (Total DOF/s %), is inversely proportional to focal length. It
can be very small for long telephoto lenses..."
Carlos
2009/11/13, CarlosMFreaza <cmfreaza@xxxxxxxxx>:
> I'd say that I learnt nothing Eric.
> Carlos
>
> 2009/11/13, Eric Goldstein <egoldste@xxxxxxxxx>:
> > Hi Carlos -
> >
> > Here is my original statement:
> >
> > > It can be argued that DOF is purely a function of aperture and not FL.
> >
> > I'm glad you were able to learn something useful from this discussion.
> >
> >
> > Eric Goldstein
> >
> > --
> >
> > On Fri, Nov 13, 2009 at 9:24 AM, CarlosMFreaza <cmfreaza@xxxxxxxxx> wrote:
> > > Yes Eric; BTW, I interpret the last part of Richard explanation: "All
> > > this given for a constant distance from the subjects" that the
> > > difference for the lenses focal length has been cancelled changing the
> > > focusing distance to the subject. It's very easy to find the equal DOF
> > > for two different lenses changing the lens FL parameter and the
> > > Subject focusing distance parameter using a DOF calculator keeping
> > > identical the COC, frame size and aperture, this was the confusing
> > > part (to me) of your original statement because since I'm changing the
> > > focusing distance to equal the DOF for two different FL, I could think
> > > that the DOF is a subject focusing distance function.
> > > Carlos
> > >
> > >
> > > 2009/11/13, Eric Goldstein <egoldste@xxxxxxxxx>:
> > >> Our Richard should be writing and teaching... he has the knack for
> > >> clarity.
> > >>
> > >>
> > >> Eric Goldstein
> > >>
> > >> --
> > >>
> > >> On Fri, Nov 13, 2009 at 7:59 AM, CarlosMFreaza <cmfreaza@xxxxxxxxx>
> > >> wrote:
> > >> > Yes, I agree absolutely, if Richard explained DOF that way from the
> > >> > beginning, the point would be clear to me from the beginning too, it's
> > >> > a knowledge that you learn using DOF calculators and cameras-lenses
> > >> > DOF indicators.-
> > >> >
> > >> > Carlos
> > >> >
> > >> > 2009/11/13 Eric Goldstein <egoldste@xxxxxxxxx>:
> > >> >> Yes. This was covered in the links I provided, but not expressed so
> > >> >> simply and elegantly.
> > >> >>
> > >> >>
> > >> >> Eric Goldstein
> > >> >>
> > >> >> --
> > >> >>
> > >> >> On Fri, Nov 13, 2009 at 3:27 AM, Richard Knoppow
> > >> >> <dickburk@xxxxxxxxxxxxx> wrote:
> > >> >>>
> > >> >>> ----- Original Message ----- From: "Eric Goldstein"
> > >> >>> <egoldste@xxxxxxxxx>
> > >> >>> To: <rollei_list@xxxxxxxxxxxxx>
> > >> >>> Sent: Tuesday, November 10, 2009 7:30 AM
> > >> >>> Subject: [rollei_list] Re: Rolleiflex 35mm Cameras
> > >> >>>
> > >> >>>
> > >> >>> It is. Another interesting discussion relative to aperture, DOF and
> > >> >>> perceived sharpness:
> > >> >>>
> > >> >>> http://www.luminous-landscape.com/tutorials/dof2.shtml
> > >> >>>
> > >> >>>
> > >> >>> Eric Goldstein
> > >> >>>
> > >> >>> Depth of field/depth of focus can be defined as either the amount
> > >> >>> of
> > >> >>> defocusing that produces a constant size circle of confusion or for
> > >> >>> a circle
> > >> >>> of confusion which is a constant percentage of focal length. When
> > >> >>> the first
> > >> >>> definition is used the depth depends only on the physical size of the
> > >> >>> aperture. Thus it will be the same for a 100mm lens at f/2.8 as for
> > >> >>> a 200mm
> > >> >>> lens at f/5.6. Where the image from the shorter lens is magnified to
> > >> >>> equal
> > >> >>> the image from the larger lens the DOF will be constant with f/stop.
> > >> >>> All
> > >> >>> this given for a constant distance from the subjects.
> > >> >>>
> > >> >>> --
> > >> >>> Richard Knoppow
> > >> >>> Los Angeles, CA, USA
> > >> >>> dickburk@xxxxxxxxxxxxx
> > >> >>> ---
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