Choosing The Right Film Speed

What is film speed?

Film speed is a measurement that indicates a film's sensitivity to light. The higher the film speed, the faster or more sensitive it is to light. So, higher speed films allow the use of higher shutter speeds (lens opening and closing speed) and/or smaller apertures (lens opening size) than do lower speed films.

Film speed comes is available indifferent ISO speed numbers, 100, 200, 400, 800, and so on.  The lower the number the less sensitive to light your film is (called a "slow" film), the higher the number (ISO 3200), the more sensitive to light your film is (called a "fast" film).

ISO and film grain are closely related, too. A higher ISO has much more of a grainy print.  A lower ISO will offer a much more clear image. Grain can be an cool effect, but can also be distracting if you didn't mean for it to be there, especially in prints larger than 5x7.

Conditions that you will be shooting in will help decide what film speed to choose:

OUTDOOR DAYLIGHT CONDITIONS
For bright situations, use a lower film speed. By using a lower ISO speed pictures will be sharper with less film grain. ISO 200 is great for bright sunlight, but is great to handle overcast days as well.

INDOOR AND LOWLIGHT W/FLASH
ISO 400 is the best indoor print film, alhough flash will still be needed for most indoor situations. ISO 400 produces  grainier images than slower films, but the images can still be enlarged to 8x10" images without the grain becoming too noticeable. It is a great choice if you are going to be shooting indoors and outdoors on the same roll of film.

Films rated ISO 800, 1600, 3200, etc. capture images very quickly, even in low-light situations. You will be amazed at the action you can catch, and the quality of your images. Although the higher films will show more grain than the slower films, the quality of the more popular films at ISO 800 is exceptionable. 1600 and 3200 are good for concerts and circuses when you may not be able to use a flash.

To recap:

100 ISO: "Slow" film Good for sunny, outdoor conditions
200 ISO: "Slow" film, good for overcast outdoor conditions
400 ISO Good compromise for indoor/outdoor use
800 ISO & up "Fast" film, Good for indoor use, low light conditions, or action shots

A word about digital "film" speed:

Obviously, your digital camera does not use film. However, most digital cameras allow you to set "ISO" speed. Although not exactly the same, digital ISO has been made to mimic film ISO, so you can use the above guidelines with your digital camera, too.

Whichever film speed you decide to use, make sure that you set your camera to the correct speed. Most cameras have DX encoding, which reads and sets the film speed automatically. If you use a flash that requires manual settings, don't forget to set the matching film speed on that as well, so that your flash will know the correct amount of light to send out.

Mostly, have fun experimenting with different ISOs, grains and effects!!