Pentacon Six System
Depth of Field
I have given an introduction to Depth of Field here. There I
explain why the depth of field is so immense with mobile
phones and most small digital cameras that differential
focus is not possible. In other words,
everything will be sharp, regardless
whether or not this is desirable. Objects in the
surroundings or in the background may be so detailed
that they distract the viewer’s attention from the
subject chosen by the photographer.
Control of what is in focus and what is out of focus
within the image only begins to become possible to some
extent with cameras that have a film or sensor format of
24×36mm (now commonly referred to as “full
frame”). Most “35mm” cameras had/have this
format. However, real control of
focus with such cameras is often only possible with
longer-than-standard lenses, for instance, with 90mm or
100mm lenses, or longer, on a full-frame 35mm camera.
For reasons explained on the above page,
control of in-focus and out-of-focus zones within the
images first becomes easy to achieve with medium
format cameras such as the Pentacon
Six. On that page I also stated:
The zone of sharp focus is
usually called “depth of field”.
Depth of field depends on three things:
- the focal length of the lens,
- its aperture
- the distance from the
The three rules are:
- The longer the focal length of
the lens, the shallower the depth of field.
- The wider (bigger) the
aperture of the lens, the shallower the depth
- The closer the camera is to
the subject, the shallower the depth of field.
Therefore, if the photographer
wishes to control the areas that are in focus in
- the longer the focal length,
- and the wider the maximum
aperture available on the lens, the better.
The distance of the
camera from the subject obviously depends on
composition and other related factors.
One area where the depth of field is especially shallow
(narrow, thin) is in macro photography, where the
lens is obviously very close to the subject.
demonstrates the depth of field that can be
obtained with the Pentacon Six, using its
standard, 80mm Biometar lens on the shortest of
the extension tubes available for the camera,
the 10mm tube. You
can find information on that tube here.
For all macro photography, the camera needs to be mounted on
a tripod, and the focussing slide (see here) is extremely helpful
to enable the camera to be moved fractionally backwards or
forwards without moving the tripod and so disturbing the
composition. For these tests I also used the angle
finder (see here)
to assist me in focussing and to enable me to view the
focussing screen from a comfortable angle.
For these pictures I chose five, small Lego figures.
This grab shot was taken hand-held with a digital
camera using a 50mm Carl Zeiss Jena Tessar lens at a
wide aperture, and it is not sharp throughout, but
it does show the setup used.
Lighting was from natural daylight entering a window
to the right, and the camera was also positioned to
the right, low down, just above the surface of the
table on which the figures were standing.
|All of these pictures were taken with
a Pentacon Six TL with the 80mm Biometar lens
mounted on the 10mm tube. The film was
Fujicolor PRO400H. A slower-speed film (for
instance, 160 ISO) would have yielded images with
finer grain, but this was the film that I had in the
camera at the time. Obviously, with
slower-speed film I would have needed to give longer
The width on the film of the images as cropped here
is approximately 37mm, or 70% of the total width of
the film frame. If I had moved closer to fill
the frame better, the depth of field would have been
Biometar on its maximum aperture of f/2.8
Shutter speed 1/30 sec
No cable release, no MLU
Focussed on 1st figure from the right.
(Using a cable release is normally to be preferred
for macro photography, but with a steady tripod and
1/30 sec I was confident that I could release the
shutter gently and not move the camera during the
Note the extremely shallow depth of field when this
80mm lens is used at its maximum aperture with the
|Focussed on the second figure from
Other settings as in previous picture.
|Focussed on middle figure.
Changing focus changes the size of the subject on
the film, something that must always happen, since
the further the lens moves forward, away from the
film (as when focussing on closer objects), the
larger the image that is projected by the lens onto
the film. In most normal photography, the
differences are so tiny as not to be observable, but
in macro photography, such differences immediately
become clear in the viewfinder.
|Focussed (approximately!) on 4th
figure from the right.
In fact, focus is probably a little too far forward,
a consequence of trying to work too fast.
Macro photography requires patience and time – and
unchanging lighting conditions, if possible!
|Focussed – supposedly! – on far-left
figure, although again focus is slightly out.
This does of course demonstrate why it is extremely
unwise to shoot at maxium aperture when doing macro
photography, since – even with perfect focus! –
depth of field is extremely shallow.
Stopping down the lens (any lens) has many
It does of course have one disadvantage (at least,
with moving subjects):
- it can mask any unintentional focussing error
- it increases the depth of field, bringing
other components in the image into sharper focus
- with most lenses it will increase the image
resolution, its sharpness and therefore its
The normal solution with moving objects is of course
to use electronic flash, which will enable the use
of smaller apertures while still achieving a much
shorter exposure that will in most cases “freeze”
any movement by the subject. However, the
flash should not normally be mounted on the camera,
since in that position it is likely to project a
shadow of the lens onto the subject! In
addition to this, evenness of illumination across
the whole of the image area must also be achieved as
far as possible, often by using two flashguns.
- the need to increase the exposure time (to
give a much longer exposure).
|Stopping down to f/16 has massively
increased the depth of field (to a depth of about 20
centimetres or 8 inches), although this is not quite
enough to encompass the full distance from the
nearest figure to the one farthest away.
As the smaller aperture lets much less light pass to
the film, I have had to increase the exposure time
to 1 second, and have of course therefore used a
cable release, to prevent the transmission of any
movement from my body (breathing! heartbeat!) to the
The depth of field extends both forward of and
behind the point of sharpest focus and as the lens
is stopped down, the increase in focus is greater behind
the point focussed upon than in front of
it. For this reason, in this image I have not
focussed on the middle figure but somewhere between
it and the image to the right of it in this picture
(the second figure from the right).
The increased depth of field now enables one to
perceive (slightly out of focus) the front edges of
the table and the point where the back of the table
reaches the wall.
|Here, without changing the point of
focus, I have stopped the lens down to its minimum
aperture of f/22, and this has increased the depth
of field and brought the farthest figure (the one on
the extreme left in the image) into sharp focus.
Naturally, I have had to double the exposure time
(to 2 seconds), to compensate for the halving of the
light intensity caused by stopping down the lens
from f/16 to f/22. Cable release used, of
|Remember that the
closer the subject on which the lens is
focussed, the shallower the depth of
field. This happens with all
lenses. In macrophotography, the
depth of field will be very shallow at
maximum aperture, and
the longer the focal
length of the lens (for instance, with a
focal length of 180mm), the
shallower will be the depth
The opposite is obviously also true: the
shorter the focal length of
the lens (for instance, with a focal
length of 50mm with the Pentacon Six), the
deeper will be the depth of
For this reason, it can
sometimes be good to use wide-angle
lenses for macro photography,
providing that you are not so close
that you either frighten your subject
or cast a shadow on it.
Thank you, Rubén and the
boys, for providing the figures for these pictures!
For more on this subject, see the pages
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© TRA First published: April 2017