Pentax SMC-FA* 300mm f/4.5 ED [IF] - Review / Lab Test Report
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Review by Klaus Schroiff, published December 2007

Special thanks to Rüdiger Neumann (1st sample) and Oliver Kirchner (2nd sample) for providing this lens!


All manufacturers have a pro league of lenses within their lineup. In Pentax land it is the silver-colored FA* series or to be precise - it was because all these lenses have been phased out in favor of the upcoming (black) DA* lenses. The Pentax SMC FA* 300mm f/4.5 ED [IF] is a representative of these older lenses. Released back in 1991 it is naturally a full format lens and when used on an APS-C DSLR it has a field-of-view equivalent to about 450mm on classic cameras.

As to be expected from a professional grade lens the build quality is excellent thanks to a durable metal lens body made and tight tolerances. Pentax implemented a focus clutch mechanism so you can change between AF and manual focusing by pushing/pulling the broad rubberized focus ring (without needing to switch the AF mode on the camera). In manual mode the focus ring operates very smooth. The lens is comparatively compact and lightweight due to a moderately slow max. aperture of f/4.5 (for a 300mm fix-focal lens). In absolute terms the lens is still fairly heavy (935g) so it is a bit surprising that Pentax decided to skip a dedicated tripod mount. When used on a tripod the setup feels slightly unbalanced (I used a 2nd tripod to stabilize the front of the lens during the formal lab tests).

The FA* 300mm f/4.5 has no internal AF motor and relies on a slotted drive screw operated by the camera. Thanks to an internal focusing system and the decoupling of focus ring and AF motor the AF speed is very high although a bit on the noisy side.

Equiv. focal length450 mm (full format equivalent)
Equiv. aperturef/6.8 (full format equivalent, in terms of depth-of-field)
Optical construction9 elements in 7 groups inc. 3 ED elements
Number of aperture blades8
min. focus distance2.0 m (max. magnification ratio 1:5.9)
Dimensions73 x 160 mm
Weight935 g
Filter size67 mm (non-rotating)
Other featuresfocus clutch mechanism