Canon EF 8-15mm f/4L Fisheye USM EF8-15mm f/4L Fisheye USM Instruction Manual - Page 8

Zooming "C" and "H" Markings Adjacent to the zoom ring, the "C" and "H" markings serve as guides to indicate the wideangle zoom position where focus is set at infinity at which photos can be created without vignetting when using EOS digital cameras installed with APS-C or APS-H image sensors. The "C"/"H" indicator on the zoom ring is aligned with either the "C" or "H" marking. Zoom Limiter The zoom limiter function allows for wide-angle photos to be created when focus is set at infinity without vignetting when using an EOS digital camera installed with an APS-C image sensor by limiting the zoom range. Activate the zoom limiter by setting the zoom ring to between 10mm and 15mm, then slide the switch towards "LIMIT." When the "C" / "H" indicator above the focus ring is aligned with either the "C" or "H" marking, there are times when vignetting occurs in the corners of an image since the size of the image circle becomes smaller when the focus position is set at close range due to the optical characteristics of this lens. The zoom limiter cannot be used if the zoom ring is set between 8mm and about 10mm (when the "C" / "H" indicators on the zoom ring are set between the "C" indicator and the wide-angle direction on the ring next to the zoom ring). ENG-7