The Olympus OM Zuiko 21mm f3.5 was one of the original lenses released with the OM1 in 1972. It is fair to say that the lens has tended to be ignored somewhat since the release of the f2 version, this was true in the days of film and it is especially true today with the current trend of mounting legacy glass on cameras such as the Sony A7r. Demand for a product dictates the price and copies of the f2 change hands on eBay for over $1000 USD while the f3.5 goes for around $350 USD. Apart from the aperture what other differences are there between the two? Well asymmetrical-type ultra wide-angle lenses are designed for optimum performance at infinity and unfortunately when used at their closest focusing distance picture quality has a tendency to deteriorate. The 21mm f2 lens incorporates a floating element system for improved sharpness from its close 0.2 meter (0.7 ft) minimum focusing distance to infinity and ensuring its superlative optical performance be extended to its closest working range. So what are the advantages of the 21mm f3.5? Well it fits Yoshihisa Maitani’s design criteria for the OM system – being lightweight and very compact. This thing is
absolutely tiny. It is about the same size as the Fotodiox OM to NEX adapter. Most other camera systems would call this a pancake lens – it’s not, it’s just that most modern DSLR cameras are very bloated and unnecessarily large. Optically it has 7 elements in 7 groups, is 31mm (1.2 inches) long, 59mm (2.3 inches) in diameter and has a filter thread of 49mm. Like most Olympus OM lenses there are different versions of the lens – the original weighed in 185g (6.5 oz) while the newer MC (multi coated) one, which is tested here, is 180g (6.3 oz) while sharing the same optical construction and exterior dimensions. Although it does not have the floating rear element of the f2 version it still focuses down to 20cm (7.87 inches) and the quality is reasonable.
Using my standard book shelf test it is immediately apparent that the lens has noticeable barrel distortion. This is not uncommon in wide-angle lenses and occurs where the image magnification decreases with distance from the optical axis and makes parallel straight lines look like the edges of a wooden barrel. These days this can be easily corrected in post. Looking more closely it is easy to see chromatic aberration on high contrast edges, again easily corrected in post. Wide open at f3.5 the centre of the image is sharp with what would now be construed as having low contrast but is actually quite good and can easily be improved on with a quick adjustment in curves. The edges are very soft and lacking in contrast – not mush but would be easily noticeable in architectural shots. At f8 the centre has improved and you can forget the thoughts of a contrast adjustment. The edges have improved but they are still not good. It is at f11 where things start to come very good, the centre is excellent and the edges are not far off. Any further stopping down and optical quality will drop off due to the effects of diffraction. Vignetting is very apparent when wide open – maybe 2 to 2 1/2 stops difference between the centre and the corners. Things improve significantly by f8. Flare is very well controlled considering the angle of view and the sun stars are quite nice considering there are only six aperture blades.
So keeping in mind this is a sample of just 1 and I have no idea if this is a good example or a bad what can I say about this lens. Well I happen to own a Canon EF 20mm f2.8 and while not one of Canon’s primo L lenses it is considered quite a respectable performer when stopped down. When we compare the two the first thing that comes to mind is the size difference. As I said before the Olympus is tiny, and it still looks small when attached to the lens adapter. Vignetting on the Canon is very well controlled, this is the big benefit of that large front element (72mm filter size compared with 49mm). Chromatic aberration is no better and no worse. It is the wide open corner sharpness where the Canon beats the little Olympus, but not hugely so and by f5.6 they are both pretty much the same. The big advantage the Olympus has over the Canon is filter use – the smaller size makes filters more affordable and I would hazard that is one of the few, if not only, ultra wide-angle lens that safely use the Cokin P system (84mm in width). My Canon still vignettes with the larger Cokin Z-Pro system (100mm in width).
Real World Examples
Well my only criticism of this lens is really nit-picking. It is just that aperture of f3.5 is a little dim and if I were to use it on an SLR (digital or analogue) it would make focusing using a split screen finder a little bit tricky. With the EVF of the A7r it makes no difference as the view can be made brighter and the focus peaking is easy to see. Probably this is not the lens to buy if you’re into astro, but if you shoot landscape and architecture as I do then it is a worthy addition to the camera bag.
The other OM lenses I’ve looked at are: