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From: David Ruether on 13 Dec 2009 14:59

"Ofnuts" <o.f.n.u.t.s(a)la.poste.net> wrote in message news:4b252229$0$30363$426a74cc(a)news.free.fr...
> On 13/12/2009 10:25, Henry wrote:

>> Before I launch myself into the wonderful world
>> of search engines, which I understand little of, I
>> thought I would be better advised first of all, to
>> start by asking those who may know more about
>> digital cameras and lenses it than I do. Some of
>> you may have used such lenses, assuming
>> they exist!
>> Henry.

> DoF depends on aperture, focal length, and sensor/film size. It is easy to put marks on a prime lens used only with a 24x36
> sensor/film, but most digital era lenses are usable and used with various sensor sizes, and zoom lenses make it even more
> complicated.
>
> However, technological evolution outside the photography word allows one to evaluate the DoF using simple tools. There is a DoF
> calculator application for Java-capable phones (and likely one for iPhones).
> --
> Bertrand

I think there is more to consider for DOF than this --
I've been an "unbeliever" when it comes to DOF scales...
Notice that when they exist on lenses (or in charts), they
symmetrically place on either side of the "correct" focus
point at a given aperture both the nearer and farther focus
points within which a selected range of "misfocus" supposedly
is permissible before the image becomes visibly soft - or the
distance range around the correct focus within which all is
supposed to be "hunkey-dorey". Baloney!;-) OK, here's why.
Imagine (or shoot) a landscape with a tree with leaves at a
great distance. Include the same type of tree much closer to
the camera. Now, using DOF scales and aperture, select the
distance setting on the lens that the DOF scale says will just
produce both good sharpness for both trees and also equal
sharpness for both trees. Print the image. You may notice that
the more distant tree that was photographed doesn't look as
sharp as the nearer one. In fact, it may look down-right fuzzy
in comparison! This is easy to explain. The "blob" size used as
a standard for "sharp point rendition" is the same in both cases,
but for the distant tree, the "blob" size represents a much
larger proportion of its size, making it appear softer. Beware
of this effect when including near-infinity landscape features.
"Almost-sharp" horizons and distant features generally don't
look very good, and you may need to "fudge" the focus a bit
toward infinity-focus and also use a smaller stop than indicated
by the DOF scales to really have good DOF coverage. BTW,
I always considered that DOF indications cheated by about a
stop..;-)
--DR


From: Better Info on 13 Dec 2009 15:36
On Sun, 13 Dec 2009 09:25:18 +0000, Henry <theeight(a)not.co.uk> wrote:

>Before I launch myself into the wonderful world
>of search engines, which I understand little of, I
>thought I would be better advised first of all, to
>start by asking those who may know more about
>digital cameras and lenses it than I do. Some of
>you may have used such lenses, assuming
>they exist!
>
>Thank you for your time.
>
>Henry.

Too bad you've saddled yourself with that SLR-design limitation. If you
check into all the CHDK capable P&S cameras, you'll find that the on-screen
EVF/LCD display (OSD) comes complete with all sorts of focal-distance and
DOF information that you need.

http://chdk.wikia.com/wiki/CHDK_User_Manual#DOF_Calculator

Just a small example of what you can include (or not) in any location on
your viewfinder's on-screen display (OSD) in any transparent colors of your
choice. There's just no going back to the limitations of an optical
viewfinder design once you find all that can be done with a good EVF/LCD
viewfinder working in conjunction with superior super-zoom optics these
days.

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