Cosina AF 100mm f/3.5 macro (Pentax) - Review / Lab Test Report
Lens Reviews - Pentax
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Review by Klaus Schroiff, published June 2007

Special thanks to Oliver Kirchner for providing this lens!


Most users are probably aware of the three third-party AF lens manufacturers (Sigma, Tamron, Tokina) but there used to be four. During the 90s Cosina entered the scene with a small lineup of very cheap AF lenses. The lenses were sold under numerous labels including Vivitar, Phoenix, Exakta, Voigtlander (not to be mistaken with the high-end SL series), Tokina SMZ (as opposed to AT-X), Cosina and probably a couple more. The whole venture wasn't a big success so Cosina decided to abandon this segment of the market again although they continue to manufacture lenses behind the scenes. Today the remaining stock of this old lens series is sold for a few bucks over at eBay. Most of the lenses aren't really interesting but there's one exception - the Cosina AF 100mm f/3.5 macro (~80-120€/US$). Regarding the comparatively slow max. aperture it is a rather unambiguous macro lens which can give you a max. object magnification of 1:2. Using the supplied "matched" macro adaptor you can even go down to 1:1 although you loose infinity focus in this case. Interestingly the lens did even catch the attention of Pentax where another variant was marketed as Pentax SMC FA 100mm f/3.5 macro for a little while. It is a full format lens and when used on current APS-C DSLRs the field-of-view is equivalent to about 150mm in classic terms.

The Cosina is sometimes described as "cream in a yogurt cup" - a quite good summary. The build quality is plain terrible. The plastic has a worrisome resemblance to the one used in kid toys - it feels both cheap and thin. It is also a mover and shaker - all moving parts are loose and wobbly. As you can see in the product images below the lens extends quite a bit when focusing towards close distances.

The AF 100mm f/3.5 macro has no internal AF motor and relies on a slotted drive screw operated by the camera. AF operations feel quite brutal but the AF speed and accuracy is actually fine.

Equiv. focal length150 mm (full format equivalent)
Equiv. aperturef/5.3 (full format equivalent, in terms of depth-of-field)
Optical construction5 elements in 4 groups
Number of aperture blades8
min. focus distance0.43 m (max. magnification ratio 1:2)
Dimensions68 x 71 mm
Weight207 g
Filter size49 mm (non-rotating)
Other features1:1 macro adapter