Film the medium on which camera records the exposure, except for digital cameras where the film is replacead by CCD or CMOS sensor.

There are varieties of film available in market:

COLOUR NEGATIVE FILMS ---- In these films the exposure is recorded on the film and what we get is called a negative where the colors recorded on the film are complementary to the original. For e.g.: the blue is recorded as yellow, red as cyan and green as magenta. When we make the print from this negative, these complementary colors get converted to original colors in the print and we see the exact scene.

COLOUR NEGATIVE FILM

SLIDE FILMS ---- Also called as reversal films, here there is no negative, what we get is the original and we can see a slide on a glass box or a projector.

SLIDE FILM

BLACK AND WHITE FILMS----here the exposure is recorded on the film as different colors are converted in top different gray tones besides black and white.

BLACK AND WHITE FILM

Then there are special purpose films available ----

INFRA RED FILMS----These films record the infrared radiations of light and what we see in our print or slide is quite different from what we see with naked eye(more in infra red photography article).

X-RAY FILMS ---- These are used to record the x rays of the spectrum and are generally used for medical purposes.

LITH FILMS ---- These are the films generally used in printing industry and producer only two tones –black or white.

Films are available in different sizes and formats according to different camera formats

1. 35mm FILMS ---- These films produce a negative equal to 24 X 36 mm and is used in all 35 mm cameras available in market.

2. APS FILMS ---- These films produce a negative of size 18 X 24 mm and are used in aps cameras.

APS FILM

3. 120 FILMS ---- These films are used in medium format cameras and produces negatives equal to the format of cameras egL: 6 X 7 in Mamiya RB and RZ series, 6 X 6 in Hassalblads, 6 X 4.5 in Mamiya 645.

120 FILM

4. 110 FILMS----These films are of same format as 120 films but are longer in length as compared to 120 films so we can get more negatives from a single film.

5. 4 X 5 INCHES SHEET FILMS----These are used in large format cameras. These films are available in sheet formats hwer3e we have to expose a single negative and then change that to put other.

4 X 5 INCHES SHEET FILM

6. 8 X 10 SHEET FILMS----These are also used in large format cameras and also come in sheet formats and we can put only one sheet in the back and before taking the other shoot have to change it.

Films have an ISO or ASA marking on it, which is nothing, but the sensitivity of the film to the light .A 100-asa film is twice as sensitive to light as compared to 50-asa film. A 400-asa film is 4 times more sensitive to light than 100-asa film.

The quality of film greatly depends on the size of grain it has. As the film is made up of the silver halide particles called grains, which are light sensitive and get exposed with light. Films with higher speed have larger grain size and thus we cannot blow up the print beyond a particular limit otherwise the grains become more apparent in the print.

Films also have exposure latitude, which is the tolerance of the film to under or over exposure. A color negative film has more latitude than a slide film. A negative film can give acceptable results at –1 to +2 stops under or over exposure respectively but in a slide film even a +/- ½ stop can make or ruin the shoot completely.

Film also has color temperature and are made to suit daylight for which the color temperature is 5500 degrees and for tungsten light for which the color temperature is 3200 degrees (more in color theory article).

Generally the films have square marks on it, which are called DX coding which helps the camera to automatically set the ISO speed in the camera and give exposure accordingly. But in some cameras we can also manually override this ISO speed when we want to push or pull the film according to our requirement.

RECIPROCITY FAILURE ----when the exposure increases above 1 sec, films generally suffer from reciprocity failure which suggests that normally the film will have to be exposed a little more than the camera suggests according to double-half principle of shutter speed and aperture.

WHICH FILM IS THE BEST???? ----Most of the people are caught by the dilemma that which film should we use and which is the best film. There is no answer to this question as this thing depends on a lot of factors and your personal preferences as well.
Firstly we have to decide for what purpose we are shooting? Do we need prints from our shoots or are the film is supposed to go for some printing purposes of catalogues or posters .if the answer is the second one then slide films the way to go as printing machines work best with slide films.
Also the type of film to use also depends on your personal preference. Do we have a projector to see our slides; are we just shooting a function from which we only needs prints so that every body should be able to see the results.
But one thing is important to know is that when we get our negatives or slides; slides is the first positive we get but in negative we have to again reverse the colors to get the original colors and there is some loss in quality, but the film technology reaching a level today we cannot see this difference normally with naked eye.