Pentacon Six: 120-140mm lenses

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

120-140mm

120mm: the 120mm Carl Zeiss Jena Biometar

At f/2.8 the Carl Zeiss Jena MC Biometar produces a very satisfactory image across the whole of the frame, for the plane focussed on. The shop signs look sharp, although the loupe does reveal a slight lack of resolving power for some very small details (e.g., the cream-coloured sign on the Tea & Coffee House sign). At f/11 this has sharpened up so that with a loupe I can read the lettering on this sign. Likewise, the roof tiles have sharpened up across the frame. At this aperture, the 120mm Biometar is as sharp and contrasty as – if not sharper than – the best of the 80mm lenses at f/11 – but then one would expect to see more detail, as the view is magnified 50% more than with the standard lens.

120mm Biometar at f/11, 1/125
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The 120mm Arsenal Vega lens

After completing the original comparative lens tests in Hitchin I purchased the Arsenal Vega 120mm f/2.8 lens. This has not yet been tested in the same place, although two pictures taken with it can be seen here.

This is what the 120mm Vega looks like:

The 120mm Arsenal Vega lens (l) and the 120mm Carl Zeiss Jena Biometar (r), each with its lens hood fitted.
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This lens has a fractionally longer focal length than the 120mm Biometar, i.e., it covers a fractionally narrower field of view. However, physically, it is hardly larger than the 80mm Arsenal Volna standard lens. See the size comparison in the image to the right here.

In November 2008 I wrote here: “unfortunately, it is not possible to close the Pentacon Six “ever-ready” case with the Vega fitted to the camera.”

In June 2019 I received an e-mail from a visitor to this website from Russia who told me,

“You can freely close the ever ready case if your helicoid on the Vega 28 retracted to the minimum.”

I checked, and this is correct. Thank you for your correction!

The Arsenal Vega 120mm lens, in the middle, compared with the Arsenal 80mm Volna standard lens, on the left, and the Carl Zeiss Jena 120mm Biometar on the right.

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However ...
Unfortunately, it is not possible to close the Pentacon Six “ever-ready” case with the Vega fitted to the camera, when the Vega has a standard Hama brand UV filter fitted and the lens cap. Removing the lens cap, but not the filter (not really an option that I would consider), I still can’t close the the camera case. If I remove the filter and replace the lens cap, it is possible to close the case – but the large, beautiful front element of the Vega is so near to the front edge of the lens that I am really not happy using the lens without the protection of a UV filter. (See picture to the right here.) The Hama filter adds approximately 5.5mm to the front of the lens. Perhaps one of the newer slim-line filters will solve the problem. Let us see. The filter that came with the lens, a Hama UV filter, is in the middle in the next picture. On its left is a newly-purchased Kenko “SMART MC UV370 SLIM” filter. On its right is a newly-purchased “Phot-R PRO MC16L DIGITAL UV SLIM” filter that was described in the listing as “Ultra Slim”, which it certainly is. [Kenko_Slim_Hama_Ultra_Slim.jpg]		The MC Vega 26B 120mm lens (in Russian: MC ВЕГА 26Б) [Vega_120_01.jpg]

Here is what the the 120mm Vega lens looks like with each of these filters in place. For this photograph, I have placed the images of the lens with the thickest filter on the left and the thinnest on the right, so the order is Hama – Kenko – Phot-R. For all three pictures I have used the same lens, focussed on infinity (which is, of course, its minimum extension). The lens has an East German rear lens cap, which I find better than the Arsenal rear lens cap. (See here.) However, the cap is of course removed when the lens is on the camera, so it is not a factor for this issue.
For the Kenko filter I have rotated the lens to enable us to see the name on the filter. The differences in thickness of the three filters is again immediately obvious. [120Vega_3fltr.jpg]		However, we now come to attaching the front lens cap to the filter. I am using the original Arsenal front lens cap for this lens: The Arsenal front lens cap, leaning against the lens [120Vega_cap.jpg]

This cap is spring-loaded, and it can be mounted directly onto the lens, or onto the front filter thread of any of these three filters, and this is where the next problem occurs.
[120Vega_Ultra_cap.jpg]		With the Hama and Kenko filters, the two spring grips of the lens cap fit within the front thread of the filter. However, the Ultra Slim filter is so slim that there is very little depth to the front thread. The cap does fit safely to the filter, but it projects forward of it, increasing the total depth of the lens+filter+cap, thus again making the closing of the Pentacon Six case difficult, even with the ultra-slim filter in place. If we could find a push-on lens cap that would push down beyond the (ultra-slim!) thickness of the filter, down onto the front of the lens, the problem would probably at last be solved! Can I close my Pentacon Six case with this combination? If I use a brand-new, unused case, which is quite hard, the answer is “no”. If I use my regular case, which has decades of use and is fairly soft and supple, the answer is “yes”. So, after all these filters and all these tests, we have a conditional “yes” to closing the Pentacon Six case with the 120mm Vega lens on the camera – depending on whether or not you use a filter, and if you do, on the thickness of the filter and the type of lens cap – and whether the camera case is nearly new and so rigid, or well-used and therefore more flexible. I do anyway prefer my well-used, flexible case, even though it has considerable signs of wear! Given the fact that the front element of the Vega lens is so close to the front surface of the lens barrel, the barrel provides no shading to the lens, so I would recommend the use of the standard Vega lens hood or shade, regardless whether a filter is used or not. You can find more information of the lens hood for the Vega 120mm lens here.

Rick Denney reports that “The 120mm Vega is nice and sharp, but not really any cheaper than the 120mm Zeiss Jena MC Biometar.” Rick has made a detailed comparative study of the rendering of out-of-focus components of images using these two and some other lenses. The technical term for the (deliberately) out-of-focus part of an image is “Bokeh”. The results of Rick’s study can be found at http://www.rickdenney.com/bokeh_test.htm. (Information correct in January 2002) 140mm
A further slight magnification of the view is afforded by the 140-280mm Schneider Variogon at its 140mm setting. Even though its maximum aperture is f/5.6, this is a very large lens. At f/5.6 the results are outstanding, both in terms of sharpness across the whole frame and contrast. There is a further increase in sharpness (and marginally in contrast) at f/11, but to see it you’d need a powerful loupe or images much larger than my 8 × 8 prints. The lens certainly deserves its outstanding reputation, and it is clear why Hasselblad users for decades have been happy with the images it produces.		140-280mm Variogon at 140mm and its maximum aperture of f/5.6! The shallow depth of field means that the front cobblestones are out of focus, but this is not due to a poor lens definition, merely a consequence of using a longer focal length lens. [C303-4]