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Band shifting (or cosmological band shifting) is the effect of redshift on photometry and other astronomical observations similarly-restricted to certain bands. Redshift shifts a source's entire spectrum to longer wavelengths, which can shift the spectrum's peak(s) from one band to another longer-wavelength band. This is the cause of dropouts, i.e., a band simply doesn't show some of the sources in the field of view. Due to cosmological redshift, this can detect sources at extreme distances, by noting which bands do not show the source. While spectrography of a particular distance source yields a better distance estimate, photometry, which requires less electromagnetic radiation from a specific source, is an efficient way to check all the sources within a field for extremely distant astronomical objects.
Band shifting also must be taken into account in analysis of such distant sources, such as estimating star formation rates of distant galaxies.