Lets review fixed wide angle photo-lens Pentax HD DA 21mm f/3.2 ED AL for Pentax K mounts. Its focus equals to 21 mm, diaphragm can be set in f/3.2 – f/22 range ( it is middle light strength lens ) with use of 7 diaphragm blades, it is designed for APS-C sensors and gives 68 degrees field of view with them. Minimal focusing distance is 0.2 m with auto-focusing support and without support of optical image stabilization ( which camera can perform itself via sensor shifting, if it has such function ). 8 lens elements in 5 groups are built into it ( it is relatively big their amount for fixed lens ), they all are covered with protective and anti-reflective multi-coating Pentax HD. 49 mm optical filters can be attached to it, its sizes are 63.5 ( diameter ) x 25.4 ( length ) mm, and mass is 119 g, it is released in 2 color variants : black and silver. Package contains : Pentax HD DA 21mm f/3.2 ED AL photo-lens itself, frontal and rear caps, carrying and storage case, 1 year warranty card and user’s guide. From one side : it is good lens with average glasses amount, average light strength, wide field of view and auto-focusing support, but from the other side : its price is quite big ( 390 USD in the middle of Autumn 2015 ). So, it should be bought only for auto-focusing with such focal distance, but if it is not needed, then it is better to buy other lens and use it via adapter or converter.
