Pentax has tonight officially announced full details of a soon-to-be-launched 25mm f/4 lens for the 645D medium-format camera.

Said to be an ideal lens for ?active outdoor photographers?, the ?ultra-wideangle? SMC Pentax-D FA645 25mm f/4 AL[IF] SDM AW boasts a dust-proof, weather-resistant build.

It is due to go on sale in the UK on 21 April, priced £3,799.99.

The lens – the second to be specifically developed for the 645D – contains 11 seals to help prevent the intrusion of dust and moisture.

?By coupling this with the Pentax 645D camera body, the user is assured of a durable, reliable digital imaging system that performs superbly in demanding outdoor settings ? even in rain or mist, or at locations prone to splashes or spray,? claimed a Pentax spokesman.

Features include a built-in pull-out type filter, Supersonic Direct-drive Motor AF system and Quick-Shift Focus.

The lens?s image circle covers the entire image area when used with 645-format film-based SLRs, according to Pentax.

The lens contains two aspherical optical elements, to minimise distortion, and is treated with an Aero Bright Coating to help prevent flare and ghosting. The latter reduces reflectance and ?greatly increases light transmittance? by forming a ‘silica aerogel layer with uniform pores’ on the surface of the optical elements, added the Japanese firm.

The newcomer should be suitable for interior shots in ‘confined spaces’, as well as landscape photography.

Read our Pentax 645D stories HERE

Pentax 25mm lens