Unfortunately, it is not possible to mount the Pentacon Six bellows on an Exakta 66 that has an Exakta 66 metering prism in place, as this projects forward of the front of the camera body and fouls the rear standard of the Pentacon Six bellows.

The following solutions exist:

• use the Exakta 66 with the non-metering prism, waist-level finder, Pentacon Six magnifying head or Kiev 60 TTL prism via the Baierfoto adapter;
• add the shortest (15 mm) extension tube behind the bellows – or indeed a longer tube if appropriate.  This has the additional advantage (if using one of the tubes designed for the Exakta 66) of switching the Exakta 66 TTL meter into stop-down metering mode, as required when using bellows.  With this setup, the bellows just clear the front of the Exakta 66 metering prism.

Image to the right: 
The Pentacon Six set up for these tests
Here with Symmar – S 5.6/180 on Pentacon Six bellows at maximum extension, with the 15 and 22.5 mm tubes.
Note the cable on the top for mirror pre-release and the spirit level in the accessory shoe to assist in getting the camera exactly level.

A solution that exploits better the focussing range of the bellows is to use the 22.5 mm extension tube behind the Pentacon Six bellows.  This gives a minimum extension with the bellows of 41.5 mm, so an additional extension of only 3.5 mm provides infinity focus with the 135mm Symmar.
 
 
 
 
 

Image to the right:
[C404-31] 135mm Symmar – S at infinity focus on the Exakta 66:
Pentacon 6 bellows & 22.5 mm tube plus 3.5mm bellows extension

 – well, it might take a little more than “one smooth turn” to rack the Pentacon Six bellows all the way out to maximum extension!

Using the 180mm Symmar with this combination also works very well.  However, the best combination when using the 180mm Symmar on the Pentacon Six bellows is of course to use the two shortest tubes: 15 mm + 22.5 mm = 37.5 mm.  Adding the minimum Pentacon Six bellows extension of 19 mm results in a total extension of 56.5 mm, so only a short additional bellows extension (5mm) is required to achieve infinity focus.

For maximum stability, the extension tube or tubes should be mounted between the camera body and the bellows (also for the purposes of clearing the Exakta 66 TTL prism housing and switching the TTL meter to stop-down metering).
 

Image to the right:
[C404-31] 180mm Symmar – S at infinity focus on the Exakta 66:
Pentacon 6 bellows with 15 mm & 22.5 mm tubes plus 5 mm extension

The M – Componons are not designed to focus at infinity but to give the maximum possible enlargement of small objects.  Maximum and minimum image sizes and reproduction ratios, plus distances from the object photographed, are included in the table below.
 
 
 
 
 
 
 
 
 
 
 

Image to the right: 
[Comp28p6min.jpg]  The M – Componon f4/28mm lens on the Pentacon Six with the bellows at minimum extension and Pentacon focussing slide.
I have had to put the stamps onto a box, as the bellows rail projects too far forward, preventing the whole set-up from getting nearer to them. 
The camera still needs to be fully levelled prior to taking the picture.
Note the difficulty of lighting the subject without casting shadows from the equipment.  In some cases it is possible to position a white card to reflect light onto the subject to reduce or eliminate shadows from the equipment.

Image to the right: 
[C404-28]  The M – Componon f4/50mm lens on the Pentacon Six with the bellows at maximum extension.
Note the cable on the top for mirror pre-release and the spirit level in the accessory shoe to assist in getting the camera exactly level.

Further details of object field widths, distances between the front of the lens and the object and reproduction ratios are given in the following table:

No vignetting occurs when these lenses are used on the Pentacon Six bellows at its maximum extension without any extension tubes – but that is a total extension of 101 mm, compared with the 167 mm maximum extension of the Exakta 66 bellows.  Even when the 22.5 mm extension tube is added to the Pentacon Six bellows, there is still no vignetting.  Adding the 22.5 mm tube and in addition the 15 mm tube (total extension = 138.5 mm) results in a tiny amount of vignetting at the very corners that is unlikely to be noticeable in most cases.  If the 30mm tube is added to these (total extension 168.5 mm) a small amount of vignetting is inevitably visible.  Not all combinations of extensions and lenses have been tested.  To be certain of having no vignetting at all, a maximum extension of about 125 mm seems advisable.  However, if the square image is to cropped to a rectangle, the small amount of vignetting with greater extensions is not a limiting factor.

The prisms produced for the Pentacon Six and the Exakta 66 (which are identical in their optical components) do not show the whole of the focussing screen, where the area of image shown is significantly closer to what is recorded on the film.

These tests show that with the Exakta 66 with Exakta 66 TTL prism, or the Pentacon Six with the Pentacon Six metering prism, the image in the viewfinder is approximately 82.5% linear of the image that appears on the film – significantly less than the approximately 90% that most SLRs from the 1970s on have aimed to show – though I notice that Hasselblad is reported as stating that the field of view in the viewfinder of its XPAN cameras is “85 per cent or more” of the image in the film gate, according to the October 1998 issue of “Practical Photography”.  Of course, this is not an SLR but a rangefinder camera, and in such cameras the difference between the image in the viewfinder and on the film can be greater than with SLRs, especially when shooting close up.  Likewise, the specification of the Voigtländer Bessa R4A rangefinder camera states that the viewfinder shows “85% of the field of view for object distances of 3 meters”.

However, when the film from any camera is printed (or mounted in a slide for projection), the edges of the frame are always slightly masked.  With the prints that were produced for me in July 2006 by a quality laboratory in London, the masking was minor, but the image in the viewfinder corresponded to approximately 88% linear of the image on the prints – very close to the target of 90%.

These figures have been arrived at by looking at the figures for all of the non-infinity images in this test, and then averaging out the results separately for the film and for the prints, to allow for any slight errors of observation of the images in the viewfinder or slight variations in cropping by the lab.

Using the Pentacon Six/Exakta 66 waist level finder, the Pentacon Six magnifier head or a Kiev 60 prism via the Baierfoto adapter enables the whole of the focussing screen to be seen.

See more about the size of the film gate here (scroll down).

To see more about the prisms, click here.