Orthochromatic

Orthochromatic ("correct colors") photographic emulsion is early emulsion, sensitive to wider range of colors than original color blind (blue sensitivie) emulsion.

Orthochromatic emulsion has too high sensitivity to blue, generally correct sensitivity to green and bright yellow, but has too low sensitivity to orange and is practically unsensitive to red.

The next step in development of color sensitivity was panchromatic emulsion.