This lens is fun to use and does for the *ist D series of cameras what the F17-28mm Fisheye zoom did for film SLR. At 10mm the angle of view is 180 degrees diagonally and provides for interesting and creative photos.
It is sharp and gives the pictures a nice 3D effect. It renders colors nicely saturated. Being a fisheye lens it has heavy barrel distorsion. The distorsion can be removed by software such as PTLens. This process will reduce the angle of view but can come in handy if you want to use the lens as a regular super wide angle.
It is constructed very well with a lens barrel of metal. Even the lens cap is of metal.
It is an autofocus lens and is also well suited to manual focusing. It has Pentax' quick focus system which provides for manual "touch up" of focus by truning the focusing ring even when the camera body is in autofocus mode.

I recommend it highly, and as you can see in the examples in this gallery, even use it for macro photo from time to time.

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