Pentax SMC P-DA 12-24mm F4.0 ED/AL (IF)

Manufacturer's Description:

"With Extra-low Dispersion (ED) glass lens element and two aspherical lens elements, the lens offers more true-to-life image reproduction. The image circle in DA-series lenses is designed to perfectly match the 23.5mm x 15.7mm size of the CCD used in PENTAX digital SLRs to optimize camera performance. The new design also contributes to a drastic reduction in size, weight and production cost, compared to 35mm-format counterparts with similar specifications."