Pentax's A-series macro lens — the 100mm f/4 with auto-aperture for K-mount close-up work.
The Pentax SMC Pentax-A 100mm f/4 Macro is a dedicated macro lens from Pentax's A-series lineup, providing 1:1 magnification on K-mount cameras. The A-series designation enables auto-aperture control in program and shutter-priority modes. At 100mm, it offers comfortable working distance for macro subjects. The SMC multi-coating ensures good contrast and flare control.
Optical performance is very good for macro work. Sharpness is excellent at close distances — the flat-field design ensures edge-to-edge clarity on flat subjects. At portrait range, the lens delivers good results with pleasant rendering. The f/4 maximum aperture is modest but adequate for macro where depth of field is always limited by the magnification.
Pentax K mount with A-series auto-aperture coupling. Filter thread is 49mm. Weight is approximately 340 grams — compact for a macro lens. Build quality is solid with metal construction and a smooth helicoid. The A-position on the aperture ring enables auto-exposure on Pentax DSLRs. Compatible with all Pentax K-mount bodies including modern K-3 III.
Available on the used market at moderate prices. Check for smooth focus ring and clean optics. An excellent macro lens for the Pentax system — the in-body stabilisation on Pentax DSLRs compensates for the lack of in-lens stabilisation. The SMC Pentax-DA 100mm f/2.8 WR Macro is the modern AF successor with faster aperture and weather resistance.