Medium Format Lenses with the Pentacon Six Mount
A comparative test
by TRA

Shift or Wide?

We have already explained (here) that in some situations what is needed is not a wider lens but just a shift lens.  On this page, we look at that further, along with the whole issue of converging verticals in architectural photography.

First, we look at a further example of an ultra-wide-angle lens, compared with a shift lens that is slightly less wide, but this time we are using a different wide-angle lens and a different shift lens.

On the page that introduces shift lenses (here), we compared a Zenza Bronica 40mm lens that had been specially-modified to Pentacon Six with a 45mm ARSAT shift lens.
On this page we compare the probably-unique Schneider-Kreuznach 40mm Curtagon for the Exakta 66 with a 45mm Hartblei shift-only lens.

More information on the 40mm Curtagon can be found, starting here.  The results of other tests with the very same 45mm Hartblei shift-only lens can be seen here.

Leeds Castle, Kent
(Yes, it is in Kent, not in the great city of Leeds in Yorkshire in the north of England.)
 Pentacon Six Fuji PRO160NS negative film 1/125 f/19


40mm Schneider-Kreuznach Curtagon lens for Exakta 66
The Curtagon gives us a great wide-angle view of the front of the castle.
However, the composition of this picture would be much better if we trimmed most of the gravel drive at the bottom of the image.
[C557_13_C.jpg]


45mm Hartblei PCS shift-only lens in Pentacon Six mount
From exactly the same position, we can see the reduction in the width of coverage when using a 45mm lens.
The Hartblei lens is here shifted 9mm up, resulting in a major reduction in the amount of the drive that is shown at the bottom of the image,
while more sky is visible than would have been the case with a non-shift 45mm lens.
[C557_12_H.jpg]

Which of these images is better?  That is of course a matter of opinion.  However, I consider that the section of another building to the right in the Curtagon image adds nothing to the image, and the expanse of gravel drive at the bottom of the image detracts from it.  Of course, if there had been a procession of ducks walking across the gravel, that might have shown the superiority of having the widest-possible lens.  Unfortunately, there were no ducks in the vicinity.  So I consider that in this instance, the 45mm shift lens gives a more pleasing image.  A tiny bit of the other building on the right can be seen, and in real life we would of course crop that out, but the purpose here is to give a fair comparison between the two lenses.  It is pleasing to note that with the Hartblei lens shifted 9mm up, there is no sign of vignetting (darkening of the corners of the image). 

However,
there are some other considerations:
  • This particular 40mm Curtagon is the only example of this lens that I am aware of in the world.
  • The 40mm Zenza Bronica lens that produced one of the pictures of St Albans Abbey that can be seen here is a custom adaptation and may well also be the only example of this lens in the Pentacon Six mount in the world.
  • This means that the widest lens in the Pentacon Six mount that one is likely to find is either the 45mm Arsenal (or ARSAT) Mir 26b, which is easy to find, or the extremely rare 45mm Mir-69 lens, reported on here.
  • If we limit ourselves to Carl Zeiss Jena lenses designed for the Pentacon Six, the widest is the excellent 50mm Flektogon, reported on the same page, here.
Of course, here we were able to stand well back from the castle, but in many situations where a wide-angle lens is required – perhaps in a narrow street or in the interior of a building – it is not possible to stand well back, and the only possible way to get the image is to use the widest-angle lens there is, whether with or without shift.

Results obtained with the Wiese shift-only version of this lens can be seen here.  The images shown there reveal what happens when the lens is shifted further than is advised for 6 × 6 format.

 

Converging Verticals and Residual Perspective

As stated in our introduction to shift lenses (here),  using a shift lens is often the best or only way of avoiding converging verticals, in which the building appears to be falling over backwards.  However, even on that page we saw, with some of the pictures of St Albans Abbey, how difficult it can be to eliminate converging verticals completely: even with an extremely wide-angle lens, or with a shift lens, one often still needs to tilt the camera up a little, to get in the top of a building, or to get a reasonable composition.

Perhaps we are sometimes too anxious about this.

When we look up at an imposing building, the verticals do converge in our view of it.  However, our brains, aware of the angle of our heads and how buildings actually are (normally with parallel walls), cleverly compensate for this, and we don’t seem to notice the converging verticals.  It is only when we look at a wide-angle picture that we notice the effect, and generally perceive it as unnatural.

Wide-angle lenses, and especially wide-angle shift lenses, enable us to reduce or even eliminate the phenomenon of converging verticals.  However, when we see a building that was obviously photographed from a low perspective, looking up, and the sides of the building are absolutely parallel in the image, our brains, which are trying to compensate for expected converging verticals, can stretch out the top of the building and generate in our mind an image where the top of the building seems to sprout out, appearing to be wider than the base, even if measurement of the components of the image would indicate that this is not the case.

I am grateful to Schneider-Kreuznach for their suggestion that – even if we have a super-wide-angle shift lens – our brain will perceive the image as more normal if we deliberately leave in what they call “Residual Perspective”.  At the time of writing this page (which is October 2018), their article on this can be found here: https://www.schneideroptics.com/pdfs/photo/PC-TS%20Anleitung%201-12%20en.PDF

The article is entitled “Schneider Kreuznach PC Tilt/Shift Lenses User Manual” and it is about the PC-TS SUPER-ANGULON 2.8/50 HM, the PC-TS MAKRO-SYMMAR 4.5/90 HM and the PC-TS APO-DIGITAR 5.6/120 HM Aspheric.  Of course, none of these lenses is for the Pentacon Six, or even for the Exakta 66, for which they produced the lenses.  The first two lenses are for “full frame” 35mm cameras, whether digital or analogue, while the third lens is for the Mamiya/Phase-One System, which covers a range of formats including Medium Format.  However, the principles do apply to us and using shift lenses on the Pentacon Six.

On the final page of this brochure, Schneider state,

“We expect that a very high object becomes smaller at the top where it is further away. It is therefore meaningful not to align converging lines completely parallel, but to leave a slight slant as a “residual perspective” in order to maintain a natural appearance.”

They continue by informing us that:

“Test shots with different amounts of keystone correction have shown that a correction of 70% to 80%, or a residual perspective of 30% to 20%, produces the most natural impression depending on the subject.”

Visitors to this website who wish to learn more about shift and tilt lenses will find a lot of interesting information in this article by Schneider-Kreuznach.  They are real experts in this area, having been producing shift and shift-tilt lenses for decades, including the 55mm Super-Angulon that they manufactured for the Exakta 66.


To see more advantages of shift lenses, continue to the

Next section (Other advantages of shift lenses)

To continue to a test of the Hartblei 45mm shift-only lens, click here.

To go back to the section on Other Accessories, click here.

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© TRA October 2018