Pentax SMC-FA 100mm f/2.8 macro - Review / Lab Test Report
Lens Reviews - Pentax
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Introduction
Analysis

Special thanks to Rüdiger Neumann for providing this lens!

Introduction

The Pentax SMC FA 100mm f/2.8 is the predecessor of the current DFA 100mm f/2.8 macro and as such obviously a discontinued lens. However, this happened fairly recently so you may still be able to find it in shops here and there (and on the used market anyway). Typical for all FA lenses it supports the full 35mm format so it can be used both on film and digital SLRs. On the Pentax K10D its field-of-view is equivalent to about 150mm (full format).

The FA 100mm f/2.8 macro is a heavy block of a lens. The outer body is obviously made of metal. The broad focus ring at the front of lens operates very smooth. Typical for most medium tele macro lenses it extends significantly when focusing towards short focus distances. The lens doesn't come with a lens hood but frankly this is also not needed because the front element is a couple of centimeters recessed from the filter thread so this "hole" serves as a sun shade anyway.

The FA 100mm f/2.8 has no internal AF motor and relies on a slotted drive screw operated by the camera. It takes quite a while if you feel the need to AF from infinity towards 1:1 magnification. In other words - the AF is a bit lame, prone to hunting and fairly noisy. However, macro users often prefer manual focusing anyway and for mainstream applications you can take advantage of the focus limiter. When restricting the AF to a range between 0.6m-infinity the AF speed is actually very fast and leaves nothing to be desired here.

Specifications
Equiv. focal length150 mm (full format equivalent)
Equiv. aperturef/4.2 (full format equivalent, in terms of depth-of-field)
Optical construction9 elements in 8 groups
Number of aperture blades8
min. focus distance0.31 m (max. magnification ratio 1:1, minimum working distance: ~10.5cm)
Dimensions75 x 104 mm
Weight600 g
Filter size58 mm (non-rotating)
Hood-
Other featuresFREE (Fixed Rear Element Extension) focusing system



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