Thanks for the link. I might have guessed it was cambridgeincolour.
There's lots of useful info on that site. I've read Merklinger's paper
some time ago but was unaware of the distribution of DOF front to back
as sensitive to focal length although I certainly knew it varied with
focus distance. Now I also know why the focal length is needed by my
DOF calculator which also tells me the front and rear limits and the
hyperfocal distance.
Although it won't modify my behavior (because I was already there with
wide angles at hyperfocal distances) this single sentence made it worth
the read: "A wide angle lens provides a more gradually fading DoF behind
the focal plane than in front, which is important for traditional
landscape photographs." Now I understand what I'm already doing a bit
better.
But there was one bit of the cambridgeincolour article that was
initially a bit confusing. He says: "The depth of field varies
depending on camera type, aperture and focusing distance, although print
size and viewing distance can influence our perception of it." Although
he redeems himself later, the implication of the statement is that print
size and viewing distance are somehow rather secondary to depth of
field. In fact, the size of the circle of confusion is the real
determinant of depth of field... and whether we can see a spot of size
equal to the circle of confusion is based on print size, viewing
distance and, of course, our own personal version of human visual
acuity. (except Moose is a special case and we'll have to leave him out
or we'll never calculate reasonable values) :-)
Chuck Norcutt
usher99@xxxxxxx wrote:
> Hi Jan,
>
> Ahh, found it:
> Quick and easy reference:? see first two tables:
> http://www.cambridgeincolour.com/tutorials/depth-of-field.htm
>
>
>
> To derive things from first principles see Merklinger:
> http://www.trenholm.org/hmmerk/TIAOOFe.pdf
>
> Near and far limits of dof:
>
> ?
> D1 = (f2D + gfD - gf2)/
> 1 = (f2D + gfD - gf2)/
> ????????? f2 - gf + gD
--
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