Best telephoto lens for the olympus pen e p5?

Here is what the site says about that.

From Olympus PEN E-P5: Olympus PEN E-P5: A mirrorless camera by Olympus with a 16.1-megapixel Micro Four Thirds sensor, announced in 2013. A metal-bodied PEN with five-axis stabilisation; the viewfinder was an optional clip-on. Specs - Maker: Olympus - Mount: Micro Four Thirds - Sensor: Micro Four Thirds, 17.3 x 13mm, crop factor 2.0 - Resolution: 16.1 megapixels - Stabilisation: in the body - Announced: 2013 - Type: mirrorless camera Focal lengths on it Lenses frame like ...

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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