[Rockhounds] achieving depth of field w digicam?

[J Bryan Kramer]

Quite right it's called diffraction limits over here. This page has an
explanation with a calculator:

<http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm>

Playing with that calculator will quickly show you why more megapixels are
not always better. Some point and shoot cameras are always diffraction
limited since the lens that they are supplied with is slower than the
diffraction limit for that camera. And also why sensor size is so important.

<http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm>

I rate myself as fairly knowledgeable in photoshop and what you are calling
stitching is not what photoshop calls it. Stitching is adding photographs
together to increase the width of the final shot, often called a panorama.
It does not increase depth of field (DOF).

Stacking has a couple of meanings but it is often used to add repeated shots
together (often used in astrophotography) to increase the exposure while
holding down camera sensor noise. In CS3 extended you can stack shots to
eliminate moving objects. For example you can shoot ten shots of some street
scene and by stacking them you can eliminate moving objects from the shot.
Subtracting the tourists and moving cars from a street scene for example.

There is a plugin to let you stack shots taken in different focal planes to
get greater DOF but that is an addon to photoshop noy something it does
normally. I don't recall the name of the plugin, I have never used it.

here is some freeware plugin software that seems to be aimed at microscopy
but might work on macro shots:

<http://bigwww.epfl.ch/demo/edf/>

BK




On Wed, Apr 16, 2008 at 2:39 PM, Axel Emmermann <axel.emmermann at pandora.be>
wrote:

> Lanny,
>
> Using f32 will reduce sharpness rather than increase it. This is due to
> refraction of light around the edges of the iris.
> You can demonstrate the effect by punching a hole in a cardboard with a
> perforator and making one with a pin or small nail. Looking through both
> of
> them at a distant object will clarify my point.
> Lenses usually perform best at mid-range f-stops... F8 or 11.
> Verily low f numbers yield low depth of field but extreme resolution of
> detail due to the above effect of refraction.
>
> Cheers
> Axel
>
> > -----Oorspronkelijk bericht-----
> > Van: rockhounds-bounces at lists.drizzle.com
> > [mailto:rockhounds-bounces at lists.drizzle.com] Namens Lanny R
> > Verzonden: woensdag 16 april 2008 18:24
> > Aan: Rockhounds at drizzle.com: A mailing list for rock and gem
> > collectors
> > Onderwerp: Re: [Rockhounds] achieving depth of field w digicam?
> >
> > Hi Tim,
> >
> > There are no magic answers with the basics of digital
> > photography; it is still bound by the same laws of the
> > physics of light.
> >
> > However, for 1-3 cm fossils (or minerals) you shouldn't have
> > a problem with that lens. Use enough light so you can stop
> > the lens down to f16 to f32 and there will be more than
> > enough depth of field for fossils of that size to be in
> > focus. The depth of field focus problem is
> > really only a problem when doing things smaller (micro fossils or
> > minerals) so that you really need to magnify them, either
> > with a microscope or extension tubes.
> >
> > On the odd occasion that you might need more depth of field,
> > shoot two or three photos to get the front and back in focus
> > and hand stitch the photos together in Photoshop or similar
> > software. It doesn't take very long to do it by hand, I was
> > doing that with micro minerals several years before automatic
> > stitching software became available. It becomes a lot of work
> > if you have several individual focus shots of each of several
> > specimens, but for just two or three shots of an occasional
> > "special" specimen, it's doesn't take very long.
> >
> > Regards,
> >
> > Lanny
> >
> >
> > On Apr 16, 2008, at 8:14 AM, Tim Jokela Jr. wrote:
> >
> > > This one goes out to the digital photography gurus out there.
> > >
> > > I was talking to a buddy last night about macrophotography of small
> > > fossils, 1-3cm stuff, and how capturing any depth of field
> > continues
> > > to be the major challenge. He suggested three ways of doing it: buy
> > > the $25,000 camera system made to do the job, take the picture 3
> > > meters away from the specimen and blow up the image, or
> > take multiple
> > > shots, focusing on different areas, and stitch them together with
> > > Helicon, Combine-Z, or the expensive new version of PhotoShop.
> > >
> > > All are basically horrible options.
> > >
> > > So, is there anything new and interesting in the world of digital
> > > photography that's giving depth of field to macrophotography in a
> > > simple, affordable manner? (My weapon of choice atm is a
> > Canon Digital
> > > Rebel with a 50mm macro lens.)
> > >
> > > Many thanks for any info!
> > >
> > > Tim Jokela Jr., tjokela at execulink.com
> > > Business: http://www.element51.com
> > > Pleasure: http://www.ontariominerals.com
> > >
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-- 
"Photography, as we all know, is not real at all. It is an illusion of
reality with which we create our own private world."
Arnold Newman


J Bryan Kramer
North Florida, USA
photos at:
http://pbase.com/photoburner


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