The other four instruments include an optical photometer and infrared spectrometers with various spectral ranges. Reflected light was measured using a pyrometer lamp as a photometer. A reflectance photometer measures the reflectance of a surface as a function of wavelength. Two types of photometers are used&colon; spectrophotometer and filter photometer. The development of the photoelectric photometer allowed precise measurements of magnitude at multiple wavelength intervals. Towed balloon, horizon scanner, photometer, infrared and ultraviolet. The photometer has a soft focus to provide excellent photometry, rather than sharp images. Ritchie's photometer depends upon equal illumination of surfaces. The antigen-antibody complexes aggregate to form particles that can be optically detected by a photometer. The optical depth of the atmosphere can be measured with a sun photometer. A multiangle absorption photometer takes into account both transmitted and reflected light. A special photometer called a hemoglobinometer measures the amount of hemoglobin. The instrument used in the procedure is called vaginal photometer. Filters select which colours the photometer detects and exclude the influence of other ions. Jan Schilt invented the Schilt photometer.