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Field Tests

50mm focal length is probably one of the most popular among photographers. Demand stimulates supply so naturally there are quite a bit of different options when it comes down to 50mm primes, with each of the modern camera/lens manufacturing offering one, sometimes even two or three different 50mm models. So why review an old, discontinued long time ago lens? What can such an old lens do what a modern lens from Canon or Nikon cannot do? Call it a nostalgia, or for more practical reasons call is a search for a cheaper quality lens. Either way, here we are, with Pentacon 50mm f/1.8 mounted on Canon 5D. Like most M42 mount lenses, the 50mm Pentacon mounts on both full frame and APS-C Canon cameras without any problems, but you would end up operating the lens in a fully manual mode, including manual focusing as well as manual aperture setting. Not a big deal if you used manual lenses in the past, but if you are switching from AF-everything camera, then you can quickly get annoyed by a few quirks like stop down metering and lack of shutter priority mode.

Once mounted on a camera, Pentacon 50mm f/1.8 feels pretty much like any other 50mm prime, however, unlike many other 50mm lenses, this one has an extremely long focusing drive. Some may call it precise focusing, I just call it long - almost 360 degrees of rotation to go from the infinity to the closeup. Some dedicated macros don't have such a long drive. More accurate focusing as mentioned is one major benefit here - the focusing drive is longer at closeup ranges, ~40 degrees to go from 33cm to 34cm, enough to give you full control over where to focus and how to position that pretty thin DOF that the lens is capable of delivering. More about this in a bit. However, the disadvantage of a such long focusing drive is that it takes quite a bit of time to rotate that darn ring to focus! QUick focusing on manual lens is hard enough, but on Pentacon 50mm it would be practically impossible, unless you preset your lens, using an engraved on the side of the barrel DOF scale.

Let's talk about DOF now. A shallow DOF and bokeh handling are often quoted as main reasons why photographers are eager to try out such old lenses as Pentacon 50mm f/1.8. Naturally, the shallower is your DOF, the better isolation you would get between the subject in focus and fore/back-ground. Combine that with rich, saturated colors, good resolution and good contrast and you have a winner on your hands. The shot below simulates the DOF you can achieve with this lens at its minimum focusing distance and wide open aperture.

 

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ISO 400, 1/640, f/1.8, 50mm (Canon 5D)

 

Well, 'this seems like a pretty thin DOF, but nothing unusual' you might say. Right... There are obviously other lenses that are capable of producing as thin or maybe even thinner DOF, but take a look at the next couple of shots done at the small beach-head off the Marine Dr in San Francisco. The completely blurred shape in the photograph on the left is the Golden Gate Bridge. Both shots were made at the minimum focusing distance. Naturally, since the bridge is much farther then the subject in focus, even f/16, shown in the shot on the right, would blur the background to some extent.

 

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ISO 100, 1/1600, f/1.8, 50mm (Canon 5D)

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ISO 100, 1/30, f/16, 50mm (Canon 5D)

 

Ok, so by now we can safely say that the lens can indeed give us pretty good separation. You can however notice, from another sample shot below, that at wide open aperture, the lens does produce pretty harsh highlighting around edges in OOF highlights. There is also a little bit of double-edging around the out of focus objects, which while not too pronounced does create a minor sense of distraction. More noticeable however is  the lack of definition, resolution that is. Now, at close focusing distances and wide open aperture, image borders are blurred so there is no point in discussing the resolution. But notice that the images taken at close focusing distances are noticeably softer then images  taken at infinity or close to infinity (just compare a couple of shots from the sample image gallery with the DOF shots above). It does seem that the lens is optimized for infinity, doesn't it? Moreover, even at infinity, image borders are noticeably soft at wide apertures - by f/4 most lenses show pretty good resolving capabilities both in the center as well as around borders, but with Pentacon 50mm f/1.8 you need to stop down to about f/8 to get a more or less uniform results across the frame. While not very desirable, you might be surprised to learn that in 60s and 70s some lens designs were developed specifically with such behavior in mind. Several famous lens designs from Leica, Zeiss and  Angenieux produced noticeably soft images at wide apertures. The main reason for that was to create rendering that softens skin tones and even adds a little bit of glow, thus creating even smoother transitions in midtones without sacrificing the overall image contrast. Now, I don't really know whether the designers of the 50mm Pentacon purposefully designed a lens that is soft around borders, or this is just a plain bad design, but the lens is noticeably soft, so you need to take this into account when using the lens and either stop it down to f/8 or f/11 and rely on some post-processing to improve the sharpness (if you want to improve it of course).


ISO 100, 1/500, f/1.8, 50mm (Canon 5D)

 

Try hard enough, and you will see flare in pretty much any lens, and the flare tests here try to stress lenses as much as possible to see where that point of failure is going to be. In many cases this means finding the most extreme situations possible, situations that are not necessarily common in your typical day to day photography. The shots below show such stressfull situation - the sun was peaking from the top of the building on the left side, with the sun rays hitting the front element at about 65 degrees. Naturally you can see flare, glare, desaturation, color streaks and ghosting all together, but again this does not mean that you would always see these results - not unless you ignore the most basic precautions. Hence there is probably no need to panic here.

 

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ISO 100, 1/2000, f/1.8, 50mm (Canon 5D)

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ISO 100, 1/200, f/8, 50mm (Canon 5D)

 

Like most fast lenses, Pentacon 50mm f/1.8 falls prone to some vignetting. At f/1.8 the light falloff is moderate on a full frame camera, but quickly disappears once you stop down to f/2.8 or so. On an APS-C body, vignetting is minimal at f/1.8 and basically non-existent for most practical uses starting with f/2.

 

Vignetting @ 50mm - full frame vs APS-C

 

The final note in the field tests is on color rendering. Color palette produced by the lens seemed a little bit warm, with some excess of yellow. The results looked sort of 'Canon'-ish rather then 'Zeiss'-ish, that is warmer tones which are quite common to Canon lenses as opposed to Zeiss lenses that tend to produce cooler gradations of color, with some excess of blue. Color aberration was pretty minimal throughout the aperture range - you can notice minor signs of longitudinal aberration in the sample shots, but nothing really drastic.

 

ISO 100, 1/6400, f/1.8, 50mm (Canon 5D)