Pentacon Six System
lens test Results
Tests of Wide Angle lenses:
coverage, linear distortion, chromatic aberrations,
sharpness and contrast
|One important area of
use for wide angle lenses is for shots of
interiors of buildings. We have therefore
here carried out tests in a domestic
kitchen. The profusion of straight lines in
the subject will be a good test of how good the
lenses are at rectilinear reproduction. In
other words, are straight lines in the subject
reproduced as straight lines on the film?
This is a very tough test for wide-angle lenses,
and for the wide-angle end of zoom lenses, which
often display barrel distortion.
For this test we wanted to get the camera
as near to the opposite wall as possible.
This made using a tripod not practical, so the
cameras were raised to the appropriate height by a
stack of books placed on the kitchen table.
The proximity to the wall also prevented us
from getting behind the camera to compose the
image, so we used the best waist-level finder that
fits the Pentacon Six, the Exakta 66 finder.
Film in both cameras was Fuji Fujicolor
Professional PRO160NS. Before starting the
session, a meter reading was taken, using the
Pentacon TTL metering pentaprism on the Pentacon
Six. This reading, 1/30th second at f/8, was
used for all photographs taken during the session
on both cameras.
In the image on the left, the
40mm Schneider-Kreuznach Curtagon for the Exakta
66 can be seen mounted on the Pentacon Six.
For more information on that lens, see here.
In the image on the right, the 45mm Pentax
67 lens is mounted on a Pentax 67II, on which we
have mounted the Pentax 67 waist-level finder.
We will here compare lenses for the
Pentacon Six / Exakta 66 / Kiev 60 with two Pentax
67 wide angle lenses on the Pentacon Six.
We will then compare the coverage on the
Pentacon Six when the same Pentax 67 lenses are
used on a Pentax 67.
The distance from the focal plane of each
camera to the centre of the subject was measured
with a metal measure and set on all lenses at
approximately 3.4 metres.
Note that these images were not taken in
a photographic studio but in a domestic environment, such
as may be encountered by many visitors to this page.
Lighting intensity and colour are therefore not uniform
across the whole image area. There are two main
sources of light:
This enters the image from a window to the left that is
partly visible is some of the wider-angle images and also
from a full-length glass door also to the left, closer to
the camera and not visible in any of the images.
There is a significant fall-off in light intensity
from left to right, and the colour balance of the light
also changes from left to right, being cooler (bluer) on
the left and warmer to the right. The fall-off in
light intensity on the right-hand side of the images also
means that any slight variations in colour between one
photograph and another are easier to see. These
variations are more probably due to the manipulation
processes involved when scanning the images and adjusting
brightness, contrast and colour on the computer.
The intensity of the daylight and its colour also
changed slightly throughout the session, as clouds moved
over an otherwise blue sky.
2. Artificial light
This comes from the downlighters in the extractor hood and
under the wall units. Although these are described
by the manufacturers as “cool”, they do not have the same
colour temperature as the prevailing daylight, being
somewhat “warmer” than daylight (with a greater yellow/red
component). Their intensity is much lower than the
prevailing daylight, so they do not have a significant
impact on the colour of the images.
In “real life”, one is unlikely to take in the region of a
dozen images of the same subject, each with a different
lens, and all of these lenses produce images of a colour
and contrast that are very good, so any variations in
colour and contrast with all of these lenses are
insignificant for most pictures.
On this page,
clicking on each image opens a larger version of the
image. With most browsers, a second click will
enlarge the image further, except in the case of the
small images of chromatic aberrations at the bottom
of the page, which will probably only enlarge once.
2 × 40mm
Zenzanon (see details of this lens here)
|Note that the shadow
in the bottom left corner of these two images is not
(principally!) vignetting (darkening of the
corners of the images); it is the shadow of a
pedal bin that is just out of the shot.
Likewise, the shadow in the top left corner is a
shadow on the ceiling from a wall unit, the door
handle of which can just be seen. The top of
this unit nearly reaches the ceiling. On the
right of the image, the closeness to the ceiling
of the top of the tall right-hand “tower” unit
containing the two ovens also darkens the ceiling
in the top-right corner. This leaves the
bottom right-hand corner, the bottom door of the
fridge-freezer, where the darkening is no doubt a
combination of the light distribution from the
window and some vignetting by both lenses.
However, the contribution of these two lenses to
the darkening of the corners of the images is
relatively minor and substantially less than one
might believe just by looking at these two
pictures without considering the other
Schneider-Kreuznach Curtagon (for details of
this lens, see the link above)
3 × 45mm
two images here are “Soviet” era lenses from
Arsenal in Ukraine. The 45mm MC Arsat B lens
on the left is a rare multi-coated post-USSR
version of the commonly-found 45mm Mir 26Б
image is from the extremely rare Mir 69Б lens,
which is much more compact than the earlier Mir
The image on the right was
taken with a Pentax 67 45mm lens mounted onto
the Pentacon Six.
Unsurprisingly, the image coverage with
the Pentax 45mm lens for 6×7 format is better on
the Pentacon Six than with the two 45mm lenses
that were designed to cover just 6×6, with far
less brightness reduction particularly visible
in the top left corner of these three images.
|45mm MC Arsat B
(= Mir 26Б) For more information on this
lens, see here.
| 45mm Mir
69Б For more information on this lens, see
| 45mm Pentax 67
lens For more information on this lens,
50mm & 2 × 55mm
lenses, three different manufacturers.
First (on the left), the Carl Zeiss Jena
50mm Flektogon designed for the Pentacon Six.
Second (in the middle), the post Soviet-era
Arsat 55mm shift lens, here in zero shift
Third (on the right), the Pentax 67
55-100mm zoom lens at its widest setting, 55mm.
| 50mm Carl Zeiss
Flektogon For more information on this
lens, see here.
| 55mm Arsat
shift lens For more information on this
lens, see here.
| Pentax 67 55mm
- 100mm zoom lens set at 55mm. For more
information on this lens, see here.
Pentacon Six coverage
compared with Pentax 67
40mm – 45mm
horizontal angle of view of the Pentax 67 camera
is obviously wider than the horizontal angle of
view of any 6×6 camera, including the Pentacon
Here we repeat for easy side-by-side
comparison the shots taken with the two 40mm
lenses on the Pentacon Six and compare the
horizontal coverage obtained with the Pentax 67
45mm lens when it is used on the Pentax 67.
We can see that the
horizontal angle of view of the Pentax 67 45mm
lens is slightly wider than the horizontal angle
of view of 40mm lenses when they are used on a
Pentacon Six or other 6×6 camera. This is
very impressive – provided that you are prepared
and able to buy a Pentax 6×7, Pentax 67 or Pentax
Zenzanon lens on the Pentacon Six
Schneider-Kreuznach Curtagon lens on the
45mm Pentax 67
lens on the Pentax 67II
as both the Pentacon Six and the Pentax 67 have
the same vertical dimension for the film, even
when the Pentax 67 45mm lens is used on the Pentax
67, it includes less height of the subject than
either of the 40mm lenses.
50mm – 55mm
Comparing image quality
|Here we compare the
horizontal angle of the 50mm Carl Zeiss Jena
Flektogon lens on the Pentacon Six with the
horizontal angle of the 55mm end of the Pentax
55-100mm zoom lens when it is mounted on the
We first repeat for easy side-by-side
comparison the shot taken with the 50mm Flektogon
Again we see that the extra width of the
film on the Pentax 67 means that more of the
horizontal dimension of the subject is included
when the 55mm lens is used on the Pentax 67II than
is included horizontally on the Pentacon Six when
using the 50mm Flektogon lens.
Obviously, with both cameras having the
same vertical dimension of the film gate,
vertically the 55mm lens includes less than the
50mm Carl Zeiss
Flektogon lens on the Pentacon Six
Pentax 67 55mm
- 100mm zoom lens set at 55mm on the Pentax 67II
curvature of straight lines
The best place to observe this in these
images is the top of the units on the far wall, where the
shadow between the units and the ceiling makes seeing the
straightness or curvature of the line particularly easy.
Rank order from best
Joint Firsts are:
|They are three lenses
from three different manufacturers (in no
The first two lenses are extremely
scarce, at least, in the Pentacon Six mount, but
the 50mm Flektogon was manufactured for nearly
three decades and is not hard to find. It
does of course have a narrower angle of view than
the two 40mm lenses, but, in spite of this, it is
still quite a wide lens, equivalent to about a
28mm lens on a 35mm “full frame” camera.
- the 40mm Bronica Zenzanon lens
- the 40mm Schneider-Kreuznach
- the 50mm Carl Zeiss Jena
40mm Zenza Bronica
40mm Schneider Curtagon
50mm Carl Zeiss Flektogon
|One of these two
lenses is from Pentax, designed for the Pentax 67,
and the other one is the 55mm Arsat shift lens
that was first marketed from about the year 2000.
In the case of the Pentax lens, there is
slightly more barrel distortion than with the
above three lenses (the
40mm Bronica Zenzanon lens, the 40mm Schneider-Kreuznach Curtagon
and the 50mm Carl Zeiss
Jena Flektogon), and the
Arsat may have slightly more distortion than the
Pentax, but there’s not much in it.
These results are naturally disappointing.
Here we see the same 45mm Pentax 67 lens
twice, first on the Pentacon Six and then on the
45mm Pentax 67 lens on the Pentacon
45mm Pentax 67
lens on the Pentax 67
55mm Arsat shift lens
|These are the two
45mm Kiev 60 lenses from the Arsenal factory in
This poor result does not surprise
us, as we had already observed it in other
tests. See, for instance, here.
- a multi-coated version of the
26Б, upgraded by Arsat
- the extremely rare Mir 69Б lens.
45mm MC Arsat B (= Mir 26Б)
45mm Mir 69Б
|This is the 55mm end
of the Pentax 67 55-100mm zoom lens.
This is not surprising. The designers
of zoom lenses struggle to eliminate rectilinear
distortion throughout the whole of the focal
length range of the lens, and this usually appears
to be impossible. The result is inevitably a
compromise, with the best point being somewhere in
the middle of the zoom range, with the wide-angle
end usually displaying barrel distortion, while
the long end of the zoom range usually displays
pin-cushion distortion (something that we have not
yet noticed with this lens).
This lens is not ideally suited to interior shots
in which long straight lines run near to the edges
of the frame.
Pentax 67 55mm
- 100mm zoom lens set at 55mm on the Pentacon
Pentax 67 55mm -
100mm zoom lens set at 55mm on the Pentax 67II
It is probably the case that all lenses have
some amount of chomatic aberrations, as each colour in the
visible spectrum has a different wavelength and so
correcting distortion equally for all colours is extremely
difficult. However, at normal degrees of enlargement
and from normal viewing distances this defect is often not
obvious. However, in some lenses chromatic
aberrations are reduced far more than in others, and we do
observe some variations between these lenses.
The lens in this test with the least
chromatic aberrations is probably the Pentax 67 45mm lens, with
the 40mm Zenzanon and the 40mm Curtagon very close to it
in quality. With the 50mm Flektogon,
chromatic aberrations are very small, although the greater
contrast delivered by this lens makes them more
visible. At 55mm, the Pentax 67 55-100mm zoom lens
shows virtually no chromatic aberrations, but it has very
45mm Pentax 67
section of the image taken with the 50mm Flektogon
lens, we see no chromatic aberrations in the
horizontal lines, but do see some in the vertical
lines. This becomes clearer because of the
fact that the Flektogon appears to deliver the
sharpest and most contrasty of the images seen
67 at 55mm
The lens in
this test with the most chromatic aberrations is the
55mm Arsat shift lens, followed by the 45mm Mir 26Б.
The 45mm Mir 69Б has slightly less
aberrations than the Mir 26Б.
45mm MC Arsat
45mm Mir 69Б
In spite of the clear presence of chromatic
aberrations with some of these lenses, studying the
whole-frame images above, even when they are enlarged on a
large screen, we observe that we do not notice these
aberrations on most occasions. That is why I here
call some results “less good”, but not “bad”.
When we examine small sections of these images
massively enlarged in order to check for chromatic
aberrations, we also observe that some lenses are less
sharp than others. It is normal for sharpness to
reduce as one moves nearer to the edge of images, and we
have here selected a section that is quite near to the
left-hand edge of the images and also not far from the
tops of the images, in other words, not far from the top
left-hand corner. All images were shot at f/8 in
order to achieve a correct exposure at 1/30 second,
without using a tripod. f/11 at 1/15 second would
undoubtedly have given sharper images, but as we were not
able to use a tripod on this occasion, this was not an
option. Again, we repeat that we only noticed these
variations when a tiny section of each image was massively
enlarged. For normal use, normal degrees of
enlargement and normal viewing distance, all of the lenses
in this test produced images that were acceptably sharp or
Are the Pentax 67 lenses better than the
equivalent Pentacon Six lenses? Yes and No!
Do the Pentax 67 lenses make a good contribution to the
potential of the Pentacon Six? Yes!
Looking at the two Pentax 67 lenses reviewed on this page,
are they better than the equivalent Pentacon Six lenses?
The 45mm Pentax 67 lens
Yes. It avoids the barrel distortion that
is clearly visible at all image sizes with the Soviet Mir
26Б and Mir
It reduces massively the chromatic aberrations that become
visible with larger image sizes when the Mir 26Б and Mir 69Б are used. It is
also, for this focal length and format, quite a “small”
The 55-100mm Pentax 67 lens at
No. The 50mm Flektogon is much better,
with virtually no barrel distortion and much higher
contrast than the Pentax lens.
However, the Pentax 55-100mm lens does offer something
that is otherwise unavailable for the Pentacon Six: a
wide-angle zoom. In less demanding situations than
this current test, the 55-100mm Pentax 67 lens will make a
valuable contribution to photography with the Pentacon
We must also remember that Pentax offers for the Pentax 67
a 55mm fixed focal length lens. Such lenses are now
commonly referred to as “prime” lenses. That lens
has not been tested, but it is reasonable to assume that
its performance will be better than that of the Pentax
wide-angle zoom lens at 55mm.