The Pentax fish-eye zoom lens has a diagonal FOV varying between 180° at the wide end and 90° at the long end. The Birds-Eye lens forms a circular fish-eye image with FOV of 180° across the image circle. All other Fish-Eye lenses form full-frame images with a diagonal FOV equal to 180°.

Field of viewmicroscope formula

The Levenhuk MED 40x infinity objective is an excellent choice for expanding any microbiologist's optical accessories kit.

Howtocalculate field of viewdiameter

The Levenhuk MED 40x infinity plan achromatic objective features 40x magnification. It is designed for infinity-corrected microscopes. The glass optics eliminate chromatic aberrations and significantly flatten the field of view. Their main feature, which makes the transmitted images sharper, is the number of optical elements. In laboratory studies, a high-quality image is required. The objective's optics are housed in a metal body, the front lens is equipped with a spring-loaded frame.

The calculator below converts between the focal length f and the field of view (FOV) of a rectilinear lens. The formula that it implements is FOV = 2 arctan (x / (2 f)), where x is the diagonal of the film. The FOV is measured across the frame’s diagonal, and is therefore smaller across the horizonal dimension, and even smaller across the vertical dimension.

Until now all Pentax DSLRs use a sensor smaller than the standard 24 x 36 mm film frame. The lens still produces a 24 x 36 mm image, but the sensor only captures the central portion of that image — your wide-angle is not so wide and your tele is even longer. The calculator below takes the 1.5 x crop factor into account.