the eyepiece, where the magnification adjustment wheel (which is absent in fixed-power sights) would otherwise be located. This is known as the rear focus (RF or R/F for short) design, and is also a somewhat favored alternative to AO designs in fixed-power sights due to the rear position of the adjustment wheel being nearer and more convenient to the user. Most telescopic sights lack parallax compensation due to cost-benefit, as they can perform very acceptably without such refinement since most applications do not demand very high precision, so adding extra production cost for parallax compensation is not justified. For example, in most hunting situations, the "kill zone" on the game (where the vital organs are located) can be so forgivingly big that a shot hitting anywhere within the upper torso guarantees a successful kill. In these sights, the manufacturers often design for a "parallax-free" distance that best suits their intended usage. Typical standard parallax-free distances for hunting telescopic sights are or as most sport hunting rarely exceed 300 yd/m. Some long-range target and "tactical-style" sights without parallax compensation may be adjusted to be parallax-free at ranges up to 300 yd/m to make them better suited for the longer ranges. Telescopic sights used by rimfire guns, shotguns and muzzleloaders that are rarely fired beyond 100 yd/m ranges will have shorter parallax settings, commonly 50 yd/m for rimfire sights and 100 yd/m for shotguns and muzzleloaders. However, due to parallax effect being more pronounced at close distances (as a result of foreshortening), sights for airguns (which are commonly used at very short ranges) almost always have parallax compensation, frequently an adjustable objective design, which may adjust down to as near as . The reason why telescopic sights intended for short range use are often equipped with parallax compensation is that at short range (and at high magnification) parallax errors become proportionally more noticeable. A typical telescopic sight objective lens has a focal length of . An optically ideal 10× sight in this example has been perfectly parallax corrected at and functions flawlessly at that distance. If the same sight is used at the target picture would be projected (1000 m / 100 m) / 100 mm = 0.1 mm behind the reticle plane. At 10× magnification the error would be 10 × 0.1 mm = 1 mm at the ocular. If the same telescopic sight was used at the target picture would