The ﬁrst ﬁlms were made of silver-halide layers which were only sensitive to blue light then along came Orthochromatic Films where the sensitivity was extended to green and yellow, and ﬁnally to Panchromatic Film which is also sensitive to red and is the most common type of Black and White ﬁlm available today. Early ﬁlm emulsion was carried on a Nitrocellulose strip which was highly ﬂammable and led to many fatalities, the Dromcollogher ﬁre of 1926 was one very tragic incident, Nitrocellulose was quickly changed to cellulose acetate a much safer material.
Orthochromatic Films (ortho for short):
Are not sensitive to red, which can be a problem in many photographic situations except when photographing foliage. One advantage with Orthochromatic ﬁlm is that it can be processed by inspection under a red safelight, which means you can also load it into developing tanks etc., under the same safelight. Orthochromatic ﬁlms can be either of high contrast or continuous tones and their resolving power is often higher than regular Panchromatic ﬁlms. But continuous tone Ortho ﬁlms are usually more expensive than Panchromatic ﬁlms, the alternative is to use ﬁlters with Panchromatic ﬁlm.
Panchromatic Film (or Pan for short):
Nearly all current black and white ﬁlms are Panchromatic as it is sensitive to all wavelengths except Infrared, you can modify the effects of Panchromatic ﬁlm by adding a ﬁlter discussed in other notes.
Designed speciﬁcally to be sensitive to one or more of the infrared wavelengths, most lenses designed for ﬁlm have a little red R next to the inﬁnity setting as you have to adjust their focusing point for the shorter wavelength.
Black & White Reversal Film:
For making B & W slides, you can buy this ﬁlm and develop it yourself or with the appropriate developer you can turn a standard B & W ﬁlm into a reversal one if you wish.
Lith Film :
A type of Orthographic ﬁlm made mostly for high contrast and continuous tone results, usually used in industrial processes e.g. for copying it can be used for other purposes such as Cyanotype, Vandyke, Kallitype etc and enlarged negatives, it can home developed with the appropriate chemicals.
Colour Negative Film:
Used for making prints, it is basically a three layer emulsion recording light in the complimentary colours of the three colour Red, Green and Blue wavelengths which are again reversed in the printing process, originally each layer had to be developed separately but this complicated process was solved by Agfa in 1936 and a single chemical developer process known as C41 is now used along with ﬁxers etc. for both industrial and home development.
Colour Reversal Film:
Used for making transparencies, it scans better than colour negative ﬁlm but does not have its dynamic range, ISO speeds are also generally lower, it can be home processed using the three bath E6 process.