Color sensitization - Irozokan

...In other words, when an emulsion is aged, its sensitivity to light outside of its original wavelength range remains almost unchanged, and in order to make it sensitive to yellow, red, or infrared wavelengths, a sensitizing dye must be added. In this way, making a photosensitive material sensitive to light in a range outside its inherent sensitivity range is called spectral sensitization (also called chromatic sensitization or optical sensitization).
[Chemical sensitization]
When a sensitizer is added to a photographic emulsion and then ripened, the silver halide crystals in the emulsion undergo a chemical reaction with the sensitizer to form sensitization nuclei within the crystals.

*Some of the terminology that refers to "color sensitization" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…すなわち，乳剤の熟成では本来の波長領域以外の光に対しては感度はほとんど変わらず，黄，赤，赤外の波長域に感ずるようにするには増感色素を加えなければならない。このように，感光物質にそれ固有の感光域以外の領域の光に対しても感度をもたせるようにすることを分光増感(色増感，光学増感と呼ばれたこともある)という。
［化学増感chemical sensitization］
　写真乳剤に増感剤を加えて熟成すると，乳剤中のハロゲン化銀結晶は増感剤と化学反応を起こして結晶中に増感核を作る。…

※「色増感」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報