  The use of wide-field multi-object fiber-input spectrographs for large
redshift surveys introduces the possibility of variations in the observed
signal-to-noise ratio across the survey area due to errors in positioning the
fibers with respect to the target image positions, leading to
position-dependent errors in the survey catalog. This paper brings together a
comprehensive description of the sources of fiber-to-image position errors in
different instrument designs, and quantifies their effects on the efficiency
with which signal is recorded. For point sources, a function relating a
fractional efficiency and an equivalent aperture correction to the
fiber-to-image position error, the fiber diameter and the image size is plotted
for typical values of fiber and image sizes found in current instruments. The
tools required by observers to maximize the efficiency of fiber-spectrographic
surveys are discussed.
