The Pentacon Six System
by TRA

Extensions & Exposure Factors
with Tubes & Bellows


The four types of extension tubes available from Pentacon:
Manual tubes in black or chrome finish (above)
and auto tubes in black or chome finish (below)
The dimensions on the black auto tubes have been added by me.
[4tubtypes.jpg]


 
The Manual Tubes

The manual tubes consist of a front tube (“A” in the image on the right) with a mount to receive Pentacon Six lenses at one end and a screw thread at the other, and a rear tube (“B” in the image on the right) with a mount to go on the Pentacon Six body at one end, and a screw thread at the other.  Each of these tubes is 9mm long, and both tubes are needed at all times, either just joined together, or with one or more of three spacer tubes of different lengths between them.

The screw thread used appears to be 68mm, apparently with the normal pitch for this size of 0.75, although I have yet to check that.

The dimensions of the other tubes are:

Tube I        8mm
Tube II       16mm
Tube III      32mm

The various combinations provide (without any gaps) image scales on film from 0.21:1 (fractionally more than one-fifth life-size) to 0.98:1 (fractionally under life-size), when used with the 80mm Biometar lens and making use of its focussing ring.

The big disadvantage of the manual tubes is that there is no automatic operation of the lens diaphragm pin, so it is necessary to open up the lens fully to focus, and then stop it down to the chosen aperture before taking the photograph.

This can be overcome by the use of the special extension tube with aperture control, and a double cable release.  This tube is 20mm long, and it can be used on its own or with the manual tubes, providing image scales from 0.24:1 to 1.02:1 (fractionally over life-size)

Here the manual tubes are being used with the special extension tube and double cable release in order to retain automatic aperture operation.

The special extension tube is labelled “Z” in the chart below.  Pentacon’s order number for this tube was 208 560.

For a long time I believed that these manual tubes were only ever available in plain metal finish outside (they are matt black inside).  However, thanks to a Pentacon collector who is a renowned expert, I now know that some manual tubes were made with a black finish.  They are seldom seen!

This chart shows the entensions obtained, image scales, image size and other information for photography using the manual tubes with the 80mm Biometar lens.

Light readings from a hand-held meter will need to be increased to allow for the increased extension between the lens and the film.  For instance, with an extension factor of 2.0, if the meter reading indicated 1/30 sec at f/4, you will need to give double the exposure, i.e.,
either 1/30 sec at f/2.8
or 1/15 sec at f/4.

In practice, depth of field is extremely shallow with macro photography, and a much smaller aperture would be recommended – either with increased light to compensate (if the image is moving) or a much slower shutter speed.

If you are use a metering prism, none of this compensation is necessary, as the meter will give you the correct reading.

Click on this table to view a larger version of it.

The Pentacon Order Number for the manual tubes was was 208 530.  You can see an illustration of the special extension tube here (scroll down).  I have called it an aperture control ring, because that is essentially what it is!

The Automatic Tubes

I recommend that if possible you obtain the automatic tubes.  These contain a plunger that transmits the camera instruction to stop down the lens aperture when firing.  The order number for the automatic tubes was 208 810.  Early versions of these tubes were produced in plain metal finish outside, although later on they were available with a shiny black finish outside.  All versions are of course matt black inside.  The dimensions of the auto tubes are as follows:
 
Tube I      15mm
Tube II     22.5mm
Tube III    30mm
Tube IV    60mm
 

In conjunction with the 80mm standard lens, these tubes provide image scales between 0.18:1 and 1.62:1.

Image scales, image size and other information for photography using the automatic tubes with the 80mm Biometar lens.

To see more information on the automatic tubes, click here.

You can see the effect of using these automatic tubes here

Click on this table to view a larger version of it.

Special Ring

There is also a 10mm extension ring which is not intended to be combined with any of the above rings; it merely fills the gap in the image scale between 0.1:1 and 0.18:1, i.e., the maximum extension of the lens (8.5mm) and the No 1 tube (15mm).  Pentacon said that if this ring is the first one to be put onto the camera, you should release the shutter before the lens is inserted and locked.  Data related to using this ring is in the above chart.

The Pentacon Order Number for the 10mm ring was was 208 811.  To see the special ring, click here.
 
Image scales & extension factors with other lenses

Pentacon also gave brief information on using the auto tubes with some other Carl Zeiss lenses.

 

Click on this table to view a larger version of it.
Bellows

The Pentacon bellows provide variable extension nominally from 20mm to 100mm and image scales with the standard 80mm lens from 0.25:1 (one quarter of life-size) to 1.25:1 (larger than life-size). 

With a double cable release, lens aperture automation is retained without the need for the special extension tube referred to above.

You can see further information on the Pentacon Six bellows here and on the Exakta 66 bellows here.

Image scales and other information for a range of bellows extensions is given in this table:
Click on this table to view a larger version of it.
For extreme close up work, it is possible to mount the 80mm Biometar lens reversed on the bellows (or for that matter, straight onto the body or one or more of the extension tubes), using Pentacon’s special reversing tube (which is illustrated here – scroll down).  This results in much greater magnification.  Here are the relevant exposure details:
Click on this table to view a larger version of it.
With the lens reversed, it is still possible to retain lens aperture automation by using the special tube described above in the section on maintaining aperture automation when using manual tubes (the “aperture control ring”).  This tube was often supplied with the double cable release.

You can see more information on the Pentacon Six bellows – and a better illustration of the set-up in this picture – here and on the Exakta 66 bellows here.

The Pentacon Order Number for the bellows was was 208 750.

The Pentacon Order Number for the double cable release was 210050


The four types of Pentacon extension tube sets, from L to R:
manual (chrome), manual (black), auto (chrome), auto (black)
(The size labels that I have added to the black auto tubes may just be visible in this picture.)
[4tubtyp2.jpg]











To go back to the beginning of the macro section, click here.

To go on to the next section, click below.
The Pentacon Six bellows

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© TRA January 2006.  Latest revision: April 2016