 |
The new-style Pentacon Six plain prism, also supplied in a smart leather case. Note that the changing dictates of style resulted in this newer case being in black leather, while the older one was in brown. [C414-4A] |
Pentaprisms
Plain prisms
Praktisix/Pentacon Six
From soon after the introduction of the Praktisix, a non-metering prism
was available, and with slight variations this continued to be available
for the Pentacon Six, so plain prisms are not difficult to find.
A few years later, an improved version of this prism was produced: a coated
condenser lens on the lower part of the prism was apparently intended to
brighten the viewfinder image substantially, although I can’t see any difference
– whether with the standard focussing screen in the camera or the much
brighter Rollei screen!
It is easy to spot whether the prism is of the older or newer design,
by looking at the button on each side of the prism that locks it onto the
camera: the original design has “silver” (bright aluminium) buttons,
while the newer prism has black ones.
|
|
The new-style Pentacon Six plain prism, also supplied in a smart leather case. Note that the changing dictates of style resulted in this newer case being in black leather, while the older one was in brown. [C414-4A] |
The prism on the Norita 66 seems to me largely inspired by the shape
of this prism – although there are of course obvious constraints on the
possible shape of pentaprisms. To see a comparison of the Pentacon
Six and the Norita click here.
 [C414-8A] |
| The older of these two prisms has in the casting of its base the KW
logo of Kamera-Werke Niedersedlitz, Dresden, the designers and manufacturers
of the Praktisix. KW had already been taken into State ownership
by the Communist government of the GDR but still used their own logo and
their own brand names (for instance, Praktina and Praktisix) on the equipment
that they made.
[C419-30] |
 |
 It is ironic that in these two examples of the prism, the Pentacon symbol of the Ernemann Tower is clear and sharp on the leather trim applied to the old KW prism (here on the right!), but fuzzy on the newer (Pentacon Six) prism, which no longer has the KW logo on its base. The older prism was obviously produced when the Pentacon name was first introduced, and used exisitng KW stock. Looking at the two cases in this picture, it can also be seen that more time and care went into the manufacture of the older case, which has a shaped insert to cushion the prism better. The original KW prism for the Praktisix did not normally have any logo at all on the leather – although I am grateful to Heinz Schrauf for a picture of a rare Praktisix prism with the KW logo on the leather:
|
Kiev 60
In the 60s and early 70s Arsenal apparently produced a non-metering
prism for the Kiev 6C, which was the precursor of the Kiev 60, but these
are extremely rare. The non-metering prism is not as tall as the
Kiev 60 metering prism.
[C436-6] The plain prism obviously lacks both the on-off switch and the metering dial of the TTL prism |
[CC436-5] The view from the other side shows, of course, the absence of a battery compartment |
[C436-7] Rear view of the Arsenal plain and metering prisms for the Kiev 6C/60 |
[C436-8] The underside of the two prisms reveals that optically they are apparently identical. Note that the non-metered prism does not have a serial number. |
Exakta 66
Exakta produced a very smart low-profile non-metering prism for the
Exakta 66, and this may still be available new from Foto Walser (see Links)
and possibly some other sources. Inside, it contains what looks like
an unmodified Pentacon Six plain prism.
 |
[C371-34A & C371-35A] Front and rear views of the Pentacon Six and Exakta 66 non-metering prisms |
Kiev 88-6 (Kiev “B.i.G.-Six”)
Arsenal have manufactured a small and light-weight
non-metering prism for the Kiev 80/Kiev 88/Salyut (also marketed in the
U.K. as the Zenith 80), and some users love it, but it is not easy to find
one.
[C442-15A] The Arsenal plain prism for the Kiev 88 This is clearly inspired by the Hasselblad NC-2 plain prism |
[C442-16A] The plain prism as supplied new in its moulded polystyrene box A protective base plate and a rubber eye-cup are supplied with the prism. |
Note that this prism is labelled “Made in Ukraine”, which dates the label, at least, at after the dissolution of the former Soviet Union. Plain prisms do not have a serial number, which – in the case of FSU products – normally indicates the year of manufacture. Like the Hasselblad NC-2 prism, the Arsenal plain prism provides 3× magnification of the focussing screen image.
[C442-17A]
The Arsenal plain prism mounted on a Hasselblad 500C
Metering Prisms
[C309-8] TTL metering prisms: L to R: Pentacon Six, Exakta 66, Kiev
60
Pentacon Six
In 1968 Pentacon introduced a TTL meter prism for the Pentacon Six,
which was henceforth called the “Pentacon Six TL”. This extremely
reliable and easy-to-operate prism provides both full aperture and stop-down
metering, though I consider that using the stop-down approach is much easier
and faster to use. The meter is not coupled to lens aperture or shutter
speed. It is criticised by some for not being very bright, although
I find it more than adequate when used with the Pentacon fresnel screen
or the Rollei screen. It is also criticised for having too wide a
“safety margin”; it just doesn’t show enough of the image on the focussing
screen. However, one adjusts to this, and if one composes tightly,
the resulting extra fraction round the edges of the image is rarely a problem,
and does at least allow for photo processors who are often not very accurate
when framing the negative to be enlarged, or when trimming the prints.
|
When not supplied with the camera, the Pentacon Six metering prism was sold in a smart leather case, and included a protective metal base plate. |
The Pentacon Six TTL prism will fit the Praktisix, the Praktisix II and the Praktisix IIA and will work perfectly with them. It has its own internal clips and so engages well even on the Praktisix and Praktisix II, which do not have the viewfinder locking pin that was introduced with the Praktisix IIA.
You can find instructions on how to use this prism here.
Kiev 60
The Kiev 60 TTL prism is also totally uncoupled, but has two advantages
over the Pentacon Six prism:
Exakta 66
| The Exakta 66 TTL prism is large, expensive and clever. Inside
its smart grey exterior hides an unmodified (as far as I can tell) Pentacon
Six prism. But here the similarities end. A series of gold-plated
contacts on the base of the prism locate with matching contacts on the
top plate of the Exakta 66 body, to provide full transfer of shutter speeds
to the electronic metering system.
The front of the prism projects forwards of the front of the camera, and another series of contacts (this time in black) mate with a rotating cam on the Joseph Schneider lenses made for this camera, transferring the value of the aperture selected to the metering prism. In addition, a pin on the Schneider lenses with a maximum aperture other than f/2.8 also tells the meter the maximum aperture of the lens. The result? Open aperture metering fully coupled to the shutter speed and aperture chosen.
|
transfer the shutter speed data |
It is not possible to mount either of the Exakta66 prisms onto the Pentacon Six.
[C309-9] The three TTL prisms viewed from above: L to R: Pentacon Six,
Exakta 66, Kiev 60
|
When the Exakta 66 Mk II was released, one of the improvements was
a longer film advance lever. This minor change was in fact a major
improvement in speed and ease of handing. However, the tip of the
new longer lever just touches the rectangular release button on the right-hand
side of the metering prism (viewed from above). In consequence, this
was re-designed to a lower-profile curved button.
(The right hand button on the newer prism is not visible from this angle, but it is of course the same as the left-hand button.) In fact, there is a third form of the Exakta 66 metering prism, but the differences are not visible without disassembling it. It contains electronic components from a different sub-contractor. |
Stop-down metering with the Exakta
66 TTL prism
Andreas Steffen of Pentacon Service in Dresden has sent me the following
fascinating e-mail (the original is on the left, with my translation on
the right):
| Sehr geehrter Herr A,
beim Ansetzen des Balgengerätes oder der Zwischenringe (Originalzubehör) wird das TTL-Prisma der EXAKTA 66 automatisch auf Arbeitsblendenmessung umgeschaltet. Eine am Balgen bzw. Zwischenring befindliche Nase, gibt einen festen Grundwert für die Blende ein. In der Kamera müssen Sie den Springblendenhebel C nach oben schwenken, damit die Objektivblende auf den eingestellten Wert schliesst. Die Einstellung wird wie üblich vorgenommen, mit dem Unterschied, dass sich die Blendenanzeige nicht verändert. Die eingestellte Blende wird in diesem Fall über das einfallende Licht gemessen (Arbeitsblendenmessung). Mit freundlichen Grüßen i. A. Andreas Steffen
|
Dear Mr A
When the bellows or extension tubes (Exakta 66 original accessories) are attached, the Exakta 66 TTL prism is automatically switched over to stop-down metering. A projecting contact on the bellows or extension tube inputs a fixed basic value for the aperture. In the camera you have to swing up the aperture stop-down lever C, so that the lens aperture stops down to the selected stop. Setting up is as normal, with the difference that the aperture display does not change. In this procedure, the light entering the camera is metered via the chosen aperture (stop-down metering). Kind regards
Andreas Steffen
|
| Notes by me:
In the instruction booklet, lever C is indicated (not very clearly!) in the first photograph of instructions (after the pages that label the parts of the camera). Swinging this lever up is described in the last of the paragraphs relating to this photo. The image on the right shows this lever more clearly. As an alternative to swinging this lever up, one can carry out stop-down metering with the Exakta 66 TTL prism (when the Exakta 66 bellows or extension tubes are mounted on the body) by pressing the stop-down lever on the lens while metering. Releasing this lever restores full screen brightness and minimum depth of field for the purpose of focussing with maximum precision. |
 |
Kiev 88-6 (Kiev “B.i.G.-Six”)
The Kiev 88 metering prism operates essentially in the same way as
the Kiev 60 prism, and is therefore not coupled to the lens aperture or
shutter speed. Only the shape and the mount are different.
It is a 45° prism, and I find it very comfortable to use. It
also has the advantage of fitting Hasselblad cameras. It offers stop-down
metering only.
[C311-12] The Kiev 88 metering prism.
Arsenal have now produced a Kiev 88 metering prism with a new design: it incorporates a spot metering option, and is highly spoken of. See Arax Foto, Kiev Camera and the other usual sources.
What a pity that these prisms and “waist level” finders are not interchangeable
between the different cameras!
But now they are! See the section on other
accessories
To go on to the next section, click below.
Next section (Viewing Aids)
To go back to the beginning of the Accessories section, click below
and then choose the accessory that you want to read about.
Back to beginning of the Accessories section
© TRA February 2002, February 2008
