Kowa Prominar MFT 25mm f/1.8 - Review / Lens Test Report
Lens Reviews -
Page 1 of 3
Review by Klaus Schroiff and Sebastian Milczanowski, published August 2015
The Kowa Prominar MFT 25mm f/1.8 is member of a gang of three new Kowa lenses for the Micro-Four-Thirds system (we covered the Prominar 8.5mm f/2.8 about a month ago). It's a "standard" lens equivalent to 50mm on full format cameras. It's reasonably fast in its class but it stays short of the conceptually similar Voigtlander Nokton 25mm f/0.95 as well as the much more affordable Pana/Leica Lumix G 25mm f/1.4 ASPH. Given this competition, the Kowa lens should better have something special - otherwise it'll be a very uphill battle.
The build quality of the Kowa lens is excellent thanks to a tightly assembled metal body and a smoothly turning focus ring. By MFT standards it is a big (to be precise: long) lens and, consequently, also quite heavy. This isn't necessarily a bad thing though - bigger is often albeit not always better (in terms of optics). Interestingly it has a couple of specialties that you don't find elsewhere. To begin with, it features a so-called "Dual Link Iris" which gives you the choice to select the aperture either in distinctive f-stop clicks (for photography) or in a smooth cine mode (T-value for movies). From this you can already conclude that the lens has no electronic coupling (no AF, no EXIF data, no camera-controlled aperture). At 25mm this is a bit of a borderline aspect because accurate focusing is not effortless here. The other specialty - or in this case it's more an oddity - is the filter thread. It is located on the lens hood (55mm). The bayonet mount is only meant to accept the lens hood. Furthermore you have the choice between three different colors - black, silver/black and green/black. The latter probably relates to a Kowa tradition because their spotting scope share the same color scheme.
As mentioned there is not much to report regarding the AF performance - because there is none. It is a fully manual lens. Apropos focus - the Kowa lens features a so-called floating system. Thus the positioning of the focus groups is optimized towards close focus distances. The max. object magnification (1:6.5 at 0.25m) is decent although this stays short of true macro functionality.
|Equiv. focal length||50mm (full format equivalent)|
|Equiv. aperture||f/3.6 (full format equivalent, in terms of depth-of-field)|
|Optical construction||8 elements in 6 groups inc. 1xaspherical and 1xXD elements|
|Number of aperture blades||9 (circular)|
|min. focus distance||0.25m (1:6.5)|
|Dimensions (L x W)||60x94mm|
|Filter size||55mm (attached to the hood)|
|Hood||barrel-shaped, bayonet mount, supplied|
|Other features||Floating system, Dual Link Iris|