Talbot was one of the earliest researchers into the field of spectral analysis. He showed that the spectrum of each of the chemical elements was unique and that it was possible to identify the chemical elements from their spectra. Such analysis was to become important in examining the light from distant stars, and hence inferring their atomic composition. He also investigated the polarization of light using tourmaline crystals and iceland spar or calcite crystals, and pioneered the design and use of the polarizing microscope, now widely used by geologists for examining thin rock sections to identify minerals within them.
Talbot allowed free use of the calotype process for scientific applications, and he himself published the first known photomicrograph of a mineral crystal. Another photomicrograph shows insect wings as seen in the "solar microscope" he and others developed for projecting images onto a large screen of tiny objects using sunlight as a light source. The large projections could then be photographed by exposure to sensitized paper. He studied the diffraction of light using gratings and discovered a new phenomenon, now known as the Talbot effect.
Talbot was very keen on applying the calotype method to recording natural phenomena, such as plants for example, as well as buildings and landscapes. The calotype technique was offered free by Talbot for scientific and amateur use. He was aware that the visible spectrum comprised a very small part of what we now know as electromagnetic radiation, and that powerful and invisible light beyond the violet was capable of inducing chemical effects, a type of radiation we now call ultra-violet radiation.