Quote Originally Posted by Ian Grant View Post
It is correct, but many early monochrome films had poorer red sensitivity, but they were fully chromatic in the case of Verichrome etc. Remember that Kodak made Verichrome right into the mid 1950's before introducing Verichrome Pan, many people preferred the look and feel of films like Verichrome it was particularly good for portraits. Adox/EFKE 25 is the closest in response to these older films.

Orthochromatic means not sensitive to the red end of the spectrum, athough the degree can vary.

Panchromatic means increased red sensitivity over films like Verichrome, Selochrome etc, Wratten & Wainwright also made Panchromatic plates before 1910, so did Lumiere.

Just about, i'd say.

First efforts were orthochromatic, only blue (and a bit of green) sensitive.
Panchromatic emulsions began to appear, and became common, in the 1910s, certainly 1920s. Verichrome was introduced in 1931, as one of the new generation of panchromatic (!) monochrome films.

The "chrome" in Autochrome however is not about spectral sensitivity, but about the image produced being in colour, and not monochromatic, and dates from the period that people were trying to figure out how to produce images in colour (1870s - 1890s).
The spectral sensitivity of the plates used however is another matter.

The use of the term "chrome" to denote slide films is due to the choice made by the manufacturers to give their slide films the "chrome" suffix, their colour negative films the "color" suffix.
Not a hard and fast rule, but still the origin of "chrome = slide".