Nine years have passed since Ethan first wrote his thoughts down about Pentax’s Limited 20-40mm zoom lens here on PhotoArk. And while he parted company with it several years ago in pursuit of other fine lenses from the Limited series, its loss to our collection left a somewhat unquantifiable hole. It wasn’t that we did not have the focal length covered; we had primes and zooms that plugged the gap. It wasn’t that the 20-40 was the sharpest tool in the box; most of our primes could best it in edge performance at most apertures. It wasn’t a speed demon either; the variable 2.8-4 aperture could be considered a little sedentary, and it didn’t have a very large zoom range, which is something it has been criticised for over the years.
Having selected Pentax as a suitable second camera system to compliment my Leica gear, an opportunity arose for me to purchase a 20-40mm lens with my K3iii at a price I could not ignore. So it was that another lens that we previously sold (the other being Leica’s TL 60mm macro) was added back into our arsenal, the only difference being that this new one was finished in silver where the previous version was a black version. Other than this they were identical; there had been no optical or design changes in the years between our ownership. This in itself is a very reassuring message.
So what is it about this zoom lens that I love enough to buy another? Starting with the zoom range, it equates to approximately 30-60mm when attached to an APSC size sensor camera. Neither true wide angle or telephoto, it covers that narrow range between both which I find invaluable for a significant amount of my work. I consider it a prime lens with a small amount of wiggle room which is sufficient to allow me to tweak composition without the need for post-process cropping. For me the 20-40 is a true ‘walk around’ lens that I particularly enjoy when travelling, which brings me to the second reason for my affection. Weighing in at just 283 grams, it is the lightest zoom that I have ever owned. My previous record for a lightweight zoom was Leica’s TL-11-23 which is a true wide angle zoom that weighs in at just shy of 400 grams with its hood attached. The 20-40’s modest aperture keeps down the element size which, in turn, helps to keep the weight down. It is also machined from lightweight aluminium that also gives the design its premium feel that is typical of all of Pentax’s Limited range of lenses. A final design point I really enjoy is the handshake with the past in the form of a zoom ring styled on classic Takumar lenses. As this is the only zoom lens in the Limited series, it is the only one that echos this aspect of a bygone design. It works very well especially for the silver version when attached to a silver K3iii.
Naturally the 20-40 is larger than other DA Limited lenses, but I do not feel it detracts from its portability in anyway. Three of the DA Limited lenses are classed as ‘pancakes’, a term used when describing very small lenses that barely protrude from the camera body. Of course these are primes, therefore optically simpler than a zoom. All of the DA Limited primes take 49mm filters but the zoom has a 55mm filter thread which can be an inconvenience if you only have a bunch of 49mm filters.
The lens hood is a very odd little thing and leaves me wondering a) if it actually helps to protect the front element from stray light and b) why, given it is just a few millimetres long, was it not designed to simply slide in and out of the lens barrel? A strange design choice indeed but as it is so unobtrusive it is a permanent attachment on my lens.
The lens cap has come in for much criticism over the years. It is beautifully made out of aluminium with the Pentax logo engraved on the front. The inner part is lined with a felt like material that affords a very snug fit. I really like the simple pull-on/off design but have found that the fit becomes sloppy with time, therefore it is very easy to loose it. I have Leica lenses that have very similar hoods and these have become loose as the inner felt lining wears away. A simple replacement clip-on cap remedies this but detracts from the lens aesthetics. Alternatively, I have added new felt to my old Leica caps which helps.
Mention should be made of the zoom’s weather sealing; it is the only DA Limited lens that has this feature. It also has a much quieter autofocus motor when compared to its siblings as it does not use the archaic screw drive method to focus.
When it comes to results, the 20-40 zoom does not disappoint. Compared to my Leica zooms, it is not as sharp, especially around the edges. But in its defence it costs a fraction of a Leica zooms. Looking at MTF values for the 20-40, the edges clearly fall off at all focal lengths and at most apertures. Viewing this information alone, it is easy to be put off wanting to try the lens. However, laboratory measurements don’t tell all of the story. Factor in how the lens draws along with how its bokeh presents itself tempers such clinical tests with real world use. Pentaxians often refer to ‘Pixie Dust’ being present in many of the Limited series lenses. I think this relates to the more intangible elements of a lens’ results, similar to what is termed as the ‘Leica Glow’. Irrespective of this property existing or not, I view it as an amalgam of strength, weakness, flaws and intention which, when combined, sometimes lend an image a certain je ne sais quoi. It is said that the 20-40 possesses Pixie Dust. Up until now, I cannot state that I agree, although I have created some very pleasing images wide open at the 40mm end which are neither extremely sharp or mis-focussed. The periphery become lost in softness, especially when the subject is woodland and focus is not set to infinity. The central area of the image is sharp but not overtly so. The colours from the RAW file are muted but not desaturated. Bokeh is not startlingly soft therefore does not distract the viewer from the subject. For my purposes, I find this very pleasing and find myself using this lens to search for subjects that allow me to exploit these properties.
Like all of the DA Limited lenses, CA is present in high contrast areas throughout most of the zoom range if used at open aperture. While it is persistent it is not troublesome and very easy to mitigate either in post processing or slightly reframing the shot when it is known that CA will manifest itself.
Vignetting presents itself fairly obviously at the wider end when larger apertures are used. At f5.6 this becomes negligible. Toward the 40mm end it is much less obvious. Like bokeh vignetting can be used creatively, so embracing this ‘imperfection’ under the right circumstances adds to the result. Many post processing tools have an option to remove unwanted vignetting very easily. I have only ever found this to be a problem when shooting images that include large areas of blue sky at 20mm. Even at f5.6 I found I had to adjust very slightly in post.
The more I use the 20-40, the more it secures a place in my heart. On two recent trips abroad, it became my most used lens, covering around 80% of my shooting. On the same two trips I was also testing the DFA* 50mm and 85mm f1.4 lenses. These are an optical tour de force that are amazing to use. I cannot praise the results from them enough and will write about each one in the coming months. As near to perfect as they may be, using the 20-40 is for me, a far more exquisite experience. Even though it is a modern lens, the design and finish takes me back to my film days. I am writing this article while scanning some of my oldest negatives. The poor efforts define my first faltering steps into the world of 35mm photography. Looking past my technically sub-standard results, the OM Zuiko lenses shone with anticipation of a time when I would get my act together to produce images worthy of their use. In those early images I can feel the essence of a more emotive experience borne out of using those analogue lenses. It is something I rarely feel today, having long sold my film equipment. A couple of Leica lenses aside, the 20-40 introduces this back into my work, hence I think, my fondness for this optic.