What is Depth of Field?
Depth of field is a range interval in front of a camera, within
which the photo appears sharp. Or to be more precise:
A regular camera can focus at one distance at a time only and
the best image definition on a photo appears for objects located
there. However, the same photo may also have tolerably sharp
resolution within an interval around this 'best' focus: That's what
we call the Depth of Field,
apparently the interval from 80 to 100
centimeters on this single-shot test photo, taken with a FocOz
camera, 3x tele lens (f=20mm) and full aperture F/2,6 focused
at 90 centimeters.
The classic way to
improve (increase) this range is to reduce the lens aperture,
i.e., increase the F-number (here to F/8).
Zooming for shorter focal
length will also do.
It works, but there are constraints:
Small apertures reduce light transmission, giving long exposure
times and as a consequence, motion blur. And too small apertures
suffer from light diffraction, degrading the image resolution.
The FocOz camera brings the nearest depth of field limit down
to 3 centimeters and all the way up to the horizon (infinity) with
full aperture and without these limitations.
Evolution of Photography
The principle of projecting an image through a small pinhole onto the
wall of a dark room (or box) may have been anticipated by ancient
Chinese thinkers, and was known more than 1000 years ago by Arab
astronomers, later improved by Leonardo da Vinci and further developed
by adding a small lens in that pinhole, becoming a camera obscura.
The invention of light sensitive emulsion made it possible to record images
permanently in the same camera obscura - giving us the first generally
useful cameras (Daguerre) from the 1830s. Development of high
resolution roll film for cameras of reduced size meant better depth of field
in so-called Fixed-Focus cameras for the general public of the next century,
and the 1977 invention of Autofocus (AF) made focusing cameras
much easier. But: Still one focus only for each exposure.
The development of large-aperture, high-resolution lenses made the Depth of
Field issue more critical again, although the recent development of
with small sensors has improved the depth of field situation to a
Extending the Depth of Field
So there we are: The old Depth of Field problem within photography is
obviously still there! But Digital camera technique provides us with a key to
remedy this problem: You may record several differently focused frames
of one and the same scene. Each of these shots has its own Depth of Field
around a focus, but they may overlap each other, together constituting a
merged continuous Depth of Field, even stretching over the whole focusing
range of a camera lens. It's feasible to do so with the FocOz camera, where
compound photos with a continuous depth of field from 3 centimeters
(Supermacro proximity distance) up to the horizon (infinity) are regularly
attempted. In order to achieve this, you must merge the differently-focused
frames in such a way that only the best focused parts from each frame are
kept for a final (processed) picture while the blurred rest is rejected.
This is done with a FocOz image processing computer program, specially
developed for this purpose.
I know that some of you may object that you don't need any Depth of Field
extension. Fair enough: Sometimes we prefer to blur a background in order
to bring out the foreground. It's an old tradition within photography to
transform this technical shortcoming into an advantage.
The Old Masters
The old masters made oil paintings with 'Infinite Depth of Field': They
painted what they saw - and their eyes accommodated (focused) onto each
individual object, depicting them sharply one after another.
The 1467 AD portrait below is an example of that (Hans Memlinc):
Even modern art shows
evidence of Infinite Depth of Field, like this AD 1998 painting
by Dietrich Varez (Hawaii) below:
Infinite Depth of Field photos, made with the FocOz camera, also have
more image information than the individual shots from which they originate.
This is indicated by reading original (jpg) file sizes for these pictures:
The merged FocOz picture file is usually bigger, as evidenced here:
It may sometimes be the purpose of a photographer to record as much detail
as possible, like at a press conference with several prominent participants
sitting along a table. Or you may wish to make a close up view of some
flowers, at the same time documenting the rest of the garden.
Here is an example:
Extended depth of field may help you in such cases, adding more
information to the photo. We have made many such shots during the past
few years and find that the extended depth of Field of a FocOz camera
adds quality, information, and appeal to a picture.
(1) a darkened enclosure having an aperture usually provided with a
lens through which light from external objects enter to form an image
of the objects on the opposite surface.
(up to "Evolution...")