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 Pentacon Six plain prism.  This one was supplied in a beautiful leather case,  seen on the right.  [C311-10]

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.
 

The underside of the two prisms certainly is different.  The newer unit (right) seems to have an extra, coated, condenser lens.  [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]

[C414-5A] Subsequent reorganisations by the GDR authorities saw KW absorbed into the new State-owned Pentacon company, and the KW name for the camera – Praktisix – was replaced by the new name Pentacon Six.  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 existing 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: Photo by Heinz Schrauf, Solingen

Kiev 60 / Kiev 6C

In the 60s and early 70s Arsenal produced a non-metering prism for the Kiev 6C, which was the precursor of the Kiev 60, but these prisms 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.

In use on the Pentacon Six, via the Baierfoto adapter, the Kiev Arsenal plain prism has the same two advantages as the Kiev Arsenal metering prism:

• it is much brighter than either of the two Pentacon prisms
• unlike them, it enables you to see the whole of the focussing screen (and a little more than that!).

Exakta 66

Exakta produced a very smart low-profile non-metering prism for the Exakta 66.  This is on rare occasions offered on the internet.  Inside, it contains what looks like an unmodified Pentacon Six plain prism.
 

Front view of the Pentacon and Exakta 66 non-metering prisms. [C371-34A]

Rear view of the same prisms [C371-35A]

Accessory socket on Pentacon Six and Exakta 66 prisms

These prisms have a mounting socket often referred to as “big ears”, because of the shape of the bayonet mounting on the accessories.  You can see that mount on an accessory here.
 

[prismeyep1.jpg] When supplied new, the Pentacon Six prisms were delivered with a rubber protector that prevented spectacles from being scratched by the eyepiece.  I don’t know why the opening in this is rectangular and not square, but in practice it permits a full view of the image, so this is not significant.

[prismeyep3.jpg] If the rubber spectacles-protector is removed, one can see the “big ears” mounting socket designed to accommodate a range of viewfinder accessories. When buying a prism, I always look for one with the spectacles-protector.

This mount can be found on the later prisms that were produced for PRAKTINA 35mm cameras, as well as on Praktica 35mm cameras in the 1960s.

Kiev 88-6 (Kiev “B.i.G.-Six”) / Kiev 88CM

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.  No Kiev 88 prism can be mounted on a Pentacon Six and I do not believe that any adapter exists to make this possible.
 

[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.

Metering Prisms

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.
 

[C372-15A]

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:

You can find instructions on how to use this prism here (scroll down).

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 those 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.

[C387-29A] Seven gold-plated contacts transfer the shutter speed data to the Exakta 66 metering prism

The aperture selected is visible in the viewfinder, and also on the top of the finder, if you prefer to look there, and + and - signs show whether you are under- or over-exposing.  A “O” indicates correct exposure.

It is not possible to mount either of the Exakta 66 prisms onto the Pentacon Six.

You can find instructions on how to use this prism here and more information on how it works here.

[C326-4A]  Exakta 66 Mk I TTL prism on the left, and Mk II prism on the right.

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

See details of this here (scroll down).

Relationship between viewfinder image and image on film, print or screen

The Pentacon Six (and therefore also the Exakta 66) prisms (both metering and non-metering) are sometimes criticised for not showing the whole of the image area.  For a detailed analysis of this, click here and scroll down to the bottom of the page.  Interestingly, the Pentax 6×7 prism is criticised for exactly the same failing on the Luminous Landscape Review, which states that
 

Kiev 88-6 (Kiev “B.i.G.-Six”)/Kiev 88CM

Arsenal Kiev has produced two metering prisms for the Kiev 88.  Both metering prisms operate essentially in the same way as the Kiev 60 prism, and therefore they are not coupled to the lens aperture nor to the body shutter speed.  Only the shape and the mount are different from the Kiev 60 prism.  Both Kiev 88 prisms are (approximately) 45° prisms, and I find both of them very comfortable to use.   They offer stop-down metering only.
 

[C311_12.jpg] The original Arsenal plain prism for the Kiev 88

[ttl_spot.jpg] The newer prism is switchable between integrated centre-weighted and spot metering. The results in both modes are absolutely “spot”-on!

They also have the advantage of fitting Hasselblad cameras.
 

[500wkspot.jpg] The Kiev centre/spot prism looks very smart on the Hasselblad 500 C/M. It compares very favourably to the Hasselblad prism shown on the right.

[500whassyp.jpg] This Hasselblad prism has a flash shoe, but that is of course about the worst place to put a flashgun! And it does not offer a spot-metering option.

Here are the weights of the prisms for the Pentacon Six, Kiev 60 and Exakta 66, with the Norita prism weights added for comparison purposes:
 

The Kiev 60 prisms are shown with and without the Baierfoto adapter (see link below) so that their comparative weight if used on the Pentacon Six can be evaluated.

Important note: I do not have scientific scales; all items are weighed on domestic kitchen scales and are valid for comparison purposes only.  You may obtain different weights with different scales, or with different examples of these items.

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
 

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© TRA February 2002, Latest revision: February 2024