Best telephoto lens for the pentax k 01?

Here is what the site says about that.

From Pentax K-01: Pentax K-01: A mirrorless camera by Pentax with a 16.3-megapixel APS-C sensor, announced in 2012. Pentax's only K-mount mirrorless camera, designed by Marc Newson, with no viewfinder. Specs - Maker: Pentax - Mount: Pentax K - Sensor: APS-C, 23.5 x 15.6mm, crop factor 1.5 - Resolution: 16.3 megapixels - Stabilisation: in the body - Announced: 2012 - Type: mirrorless camera Focal lengths on it Lenses frame like 1.5 times their focal length ...

From Sensor sizes: What it costs you: - Size, weight and price, especially of the lenses. A full-frame telephoto is much larger than its APS-C or Micro Four Thirds equivalent. - Less depth of field when you want more of it, for macro or landscape.

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