The following chart presents a comparison between basic parameters of the M.Zuiko Digital ED 90 mm f/3.5 Macro IS PRO and these of other macro lenses designed for mirrorless cameras which focal length, converted to full frame, amounts to at least 100 mm. The newest OM System product is here the slowest aperture-wise but also it is the only one that offers you the 2:1 mapping scale.
When it comes to weight and physical dimensions the OM 90 mm f/3.5 is a real midget – only the Olympus M.Zuiko Digital 60 mm f/2.8 ED Macro is smaller in this group.
In the photo below the OM System M.Zuiko Digital ED 90 mm f/3.5 Macro IS PRO is positioned between the Canon EF 100 mm f/2.8L IS USM Macro and the Voigtlander Nocton 25 mm f/0.95. When you compare the new OM 3.5/90 to a macro lens designed for reflex cameras it doesn't seem so small any longer.
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The tested lens starts with a metal mount that surrounds contacts and a black, well matted inner tube. Inside the tube you see a rear element that doesn't move and is about 19 mm in diameter.
The proper body of the lens starts with a smooth, metal ring with a red dot, making an alignment with a camera easier, inscriptions with the name and parameters of the lens, information that this instrument is splash proof, its mount and the minimum focusing distance in the macro mode (0.25m/0.82ft-∞) and the S-MACRO mode (0.224–0.5m/0.735–1.64ft).
Further on you encounter a dark blue ring, characteristic for the PRO series, that turns smoothly into a part of the barrel which doesn't move. Then you see a whole series of switches. The first one is used for choosing autofocus range, with three options: S-MACRO, 0.25-0.5 m, and 0.25m-∞. The second switch controls optical stabilization (IS ON/OFF), and the third is an L-Fn switch that can be alloted many functions from the camera menu level.
A big manual focus ring, covered by ribs, is the next part of this lens. It is 37 mm wide and offers you two modes, a default mode, electronically enhanced, or a fully manual mode, available after shifting the ring toward the mount. After that a mapping and traditional distance scale is revealed, including the full range of the lens with the S-Macro mode. The focus throw in the manual mode amounts to a bit over 100 degrees; in the electronic mode this angle increases to significantly over 500 degrees.
When you work in the ordinary macro mode, at a distance of 0.25 of a meter the front element is situated 12 cm from the object. After passing to the S-MACRO and the 2:1 mapping that value decreases to about 6 cm.
Taking photos in the S-MACRO scale the minimum aperture value you are able to set is f/5.0. It stemms from the fact that macro lenses get 'slower' when you pass to higher mapping scales. Official information of the producers states precise aperture values for particular distances. In 1:1 scale at 0.25 of a meter it is f/6.3 ad in the 2:1 scale at 0.224 of a meter the efficient aperture increases already to f/8.0.
A narrow, metal ring with a dark blue band, with the name and parameters of the lens on it, is the next part of the instrument.
The front element of the lens doesn't move, it's relatively flat, and its diameter amounts to 29 mm. It is surrounded by an immobile, ribbed tube that turns into a non-rotating filter thread, 62 mm in diameter, and a hood mount.
When it comes to optical construction you deal here with 18 elements positioned in 13 groups and there are plenty of special elements among them. You get as many as 4 elements made of low dispersion ED glass, two made of Super ED glass, one made of HR and one of Super HR glass. Inside there is also a round aperture with nine blades that can be closed down to a value of f/22 at the maximum. What's interesting, after attaching the teleconverter the maximum aperture value doesn't change, still amounting to f/22.
Buyers get in the accessory kit: both caps, a hood, and a soft pouch (also called a wrap).
Optical stabilization
As we mentioned in the introduction, the producers boast of the fact that you can combine optical stabilization modules of the lens and the camera's sensor, reaching a very high efficiency of 7 EV.
To be honest such claims seemed to us a bit over the top – they would mean that, with a lens of such focal length, we should be able to take sharp photos employing exposure times of 0.5-1 second. We tried such a trick, in vain. In order to determine the real efficiency of the stabilization unit we decided to take several dozen of photos for exposure times ranging from 1/200 to 1/2 of a second with the optical stabilization switched on and off; then we determined the percentage of out-of-focus shots for every time of exposure. That percentage was presented as an exposure time function graph, expressed in EV, where 0 EV is an equivalent of 1/160 of a second.
As you can see, the maximum distance between both curves reaches 4.3 – 4.5 EV and so we assess the efficiency of the stabilization unit. It's far lower than official declarations but, nevertheless, it remains an excellent result.
