I think the student has long ago surpassed Dr. Focus.
Chuck Norcutt
On 8/31/2011 10:34 AM, usher99@xxxxxxx wrote:
> Thanks for looking and commenting Chuck.
>
> The 10 yr old book given to me with the Paph orchids used
> illustrations obtained by flash at small apertures with an artificial
> smooth background.
> They were OK only but served the purpose. I would have been much
> pickier, but it would not have been published until the next millennium.
>
> As AG pointed out in the past, you know things are slow when the dof
> thread appears.
> Learned from Dr. focus long ago that FL has little effect on total dof,
> but shorter FL have a greater percent in the rear--distal to the focal
> plane.
> The "absolute blur" as defined by the by the blur disk diameter of a
> point in the background is larger for longer focal
> lengths but the "relative blur" is the same--after adjusting for
> different mag. Thus the longer FL background will be smoother as per
> CH.
> Part of this is also that the background area is more restricted by the
> AOV.
> A curious note in the Nasse article is that with distant backgrounds
> the absolute blur is a f(physical lens aperture) and not really the
> lens design.
>
> Nasse frim Zeiss in his e-mail said an experienced photogs would
> correctly ignore full wave dof solutions to their lenses (or something
> to that effect)
> so they don't provide them. So he was wearing his "I agree with Moose"
> T-shirt that day. I have no clue why they do provide them for the
> cine lenses.
>
> Hope others liked the orchid. :-)
>
> Trying to be in critical focus, Mike
>
>
--
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