[Rockhounds] achieving depth of field w digicam?

[Axel Emmermann]

Hi Rik, 
 
> (which does not mean that we aren't 
> good friends :>).

Damn right we are ;-)))
 
> 1.	When we look at a specimen and we need a depth of view, 
> we move, turn etc. the specimen, and our brain/memory
> makes a stack of the images, creating in that way a more or 
> less 3-D view of the specimen. Stacking software does
> (about) the same thing on a photo.

Already I protest ;-))
When you turn YOUR specimen you get the above effect. When you look at A
specimen, it is usually on a shelf behind glass. You look at it and that is
the end of stacking. You can kinda scan the object by moving the focus of
your eyes back and forth but at any given time you see only part of it sharp
unless it's a big object at some distance.
That is also how the photo should look to resemble reality.
Reproducing reality is what makes photography art. Digital imaging is what
devaluates photography to the level of a xerox machine. Anyone can make a
1000 images a day and hope there's 1 or 2 acceptable among them. With
stacking software you don't make a photo, you flatten reality to something
that is impossible and surreal. You crunch 3 dimentions into two.

> 2.	When we take an analogous photo (meaning : with a 
> classical camera, on film) we narrow artificially the
> aperture, and use a much higher exposure time to obtain a 
> higher depth of focus (taking into account Axel's arguments 
> in his second message). Stacking software pursues the same 
> goal, using different means.

A good photographer will strive to use an aperture that is as wide as
possible to move the plane of attention towards the object and blurr out the
unimportant detail.
The ambitious amateur wants to rival that and is fooled into believing that
expanding the depth of field is by all means preferable. 

> 3.	Imagine that you would be able to have a heterogeneous 
> lens, meaning that the focal distance would change
> gradually from the centre towards the edge of the lens, than 
> you would be able to make a photo where a crystal in the 
> centre would be sharp in focus, and the background material 
> towards the edges of the lens as well, because the focal 
> distance would be adapted. Of course, such a lens would have 
> to be designed just to take one photo :>)  Such a photo would 
> not be considered as "not permissible"... however the only 
> difference would be that other means have been used for 
> (something like) the same result as if you follow the way of 
> stacking software.

There are no such lenses but there are bellows that can be tilted and turned
at both sides obtaining similar result. They are used for mainly technical
purposes wher DOF is important and some art photography.
Why are they used instead of stacking software? RIGHT, the photographer
STILL reserves the right for himself to choose were his photo is in or out
focus. There are plenty of examples on the internet.
http://www.pentaxforums.com/forums/pentax-slr-lens-discussion/24004-my-self-
made-tilt-shift-bellows.html
Look at the flower on this page:
http://www.outdoorphotographer.com/content/2007/july/macro.shtml
Not stacked, just tilted lens. The flower is sharp as it should and the rest
is beautifully out of focus.
I rest my case.

> 4.	The depth of focus of our eyes is far better than that 
> of a camera. 

No, it's not nearly as good as a good technical camera can achieve.


> This means that a photo (not stacked) does
> show in fact even less than your eyes would see directly. In 
> fact the depth of focus of human eyes is perhaps not "far 
> better", but the brains combine the images of both eyes... in 
> fact what we see is a "stack" of two images... a photo shows 
> only one image instead of a combination of two.

I don't agree (but you knew that) ;-)))
You don't SEE more with both eyes!
Your brain actually fills in the gaps just like the "unshap mask" filter
does in photoshop. You think you see more but you may in fact see things
that only appear to be there. That is how we actually recognize faces. We
look at mouth, eyes and nose and the brain fills in the rest in a few
thousands of a second. But sometimes the brain fails and we mistake people
for someone else.

> 5.	Any photographer would have no objection to a 
> photographic panoramic view. Again, this is an example of
> something that we would not be able to see with our eyes. 

We see about 180 degrees or so. Try that with a fish-eye lens and look at
the ridiculous amount of distortion. You seriously underestimate our eyes,
Rik.

> 6.	The purpose of a photo has, IMHO, always some 
> didactical purpose, and therefore, the more detailed information
> one can show clearly in one photo, the better. Even if that 
> necessitates the use of stacking software. On the condition, 
> however, that nothing is shown that wasn't there in reality. 
> Then it would become fake.

Photography means "painting with light", creating a facsimile of reality.
Reality is dicontinous. It is like a string of pearls where each pearl is a
moment in time. You scan the depth of the object you perceive in limited
time frames (about 1/30 of a second per frame).
A photo HAS to be a pearl. What you see at ONE monent in time. Only then can
it be a true representation of the world that we see. You can't focus on
every distance at once so any close-up photo that is in focus all over has
to be a fake

> 7.	Perhaps the most important of my arguments is that a 
> stacked composition of photos shows nothing that was not
> really present, therefore for me nothing is wrong with such 
> type of imaging.

You confuse a photo with a movie. There you can zoom in without violating
reality.

> And I admit that there is, as always, some sort of a gray 
> zone : what about the correction of a wrongly tuned color 
> temperature ? 

Why would you do that when you used the right camera setting and the right
lighting?

>What about enhancing sharpness, 

That you can't do. There are PS-filters that EMULATE the effect by merging
pixels and adjusting this and that... Ultimately you CREATE (and I have
demonstrated that on several occasions) artefacts that are not there. Lines
and grooves that are simply create by your software suddenly appear and your
photo seems so much richer in detail...that wasn't there in reality. Enough
licht to subdue noise and take the time to focus.... Those are the tricks
that make a photo sharp.


>contrast etc ? 

RE-Why would you do that when you used the right camera setting and the
right lighting?

> What about the use of a "soft focus" lens, that reduces 
> sharpness artificially ? Those things are done digitally, but 
> were done as well in the dark room in the last century.
> Also in analogous photography many techniques produce images 
> that are not exactly as the naked eye would see.

Art, Rik... Art... Art has no foothold in reality unless and only so far sa
the artist deems in appropriate.

> On the other hand I want to emphasize on the fact that I 
> don't even have any stacking software, and so far I did never 
> use it. Since the time I have a decent digital camera I did 
> not have the time to do much about photography of minerals.
> So I am not defending "my technique".
> I hope to get to mineral photography as soon as I will retire 
> (that is 1 July 2010).

We rejoice in the prospect ;-)))
I'm sure you'll have our full attention. 

> And of course, this is just my opinion and interpretation of 
> things, not the absolute truth. I think that this discussion 
> is fruitful as such, and everyone has to distill his own 
> conclusions from it.

NOW we agree (roflmao).
It was fun refuting you... This seems to be an never-ending story... 

Cheers my friend
Axel