A lens system, an interchangeable lens apparatus, and a camera system each include a front group including a first focus lens group that moves with respect to an image surface in focusing from an infinity in-focus condition to a close-object in-focus condition; a rear group including a second focus lens group that moves with respect to the image surface in focusing, the front group and the rear group being located in order from an object side to an image side; a fixed lens group including at least one positive power lens element, the fixed lens group being located between the front group and the rear group and fixed with respect to the image surface in focusing; and an aperture diaphragm. The positive power lens in the fixed lens group satisfies dPgF>0.015 (dPgF is an anomalous dispersibility in a g-line and an F-line of the lens element).