Photography - Film Types and Film SpeedWriten by Danny Hartley
The final result of your photographic ventures is a roll of film, a handful of prints or a box of slides. Other than your choice of lens, the film choice will have the biggest impact on the quality of the final results.
DIGITAL CAMERAS
While most of this is irrelevant for digital cameras, film speed still applies. In this case the speed affects the noise level rather than grain size but the final result is somewhat similar. Choose the smallest ISO for the required shutter speed, ie to allow hand-held shooting or freezing sports action.
CHOOSING A FILM
1. First choice is slide (positive) or print (negative) film.
Print
greater exposure latitude (some 9 stops vs 5 stops for slide)
cheaper
easy for prints
ideal for cheap compact cameras
Slide (also known as reversal or tranparency film)
greater colour saturation and contrast (especially professional film)
no middle-man adjusting colour balance or exposure
much easier to digitise
requires good camera to obtain correct exposure
As slide film has 5 stops of latitude, correct exposure is much more critical than print film. This means the use of a camera with a precision auto-exposure meter such as an SLR (or very good compact) or using a light meter.
Black and white film is all negative nowadays. There was a wonderful black and white slide film offering from Agfa called Dia Direct. Now long discontinued. There are some techniques for creating B+W slides from negative film.
Slides are also a better choice if you want to take film pictures and then digitise them. Negatives are notoriously difficult to colour correct after scanning. You can look at the slide and compare with the digitised version to get an accurate colour balance. Prints do not give you a valid reference point!
Summary: if you want prints go for print film. Slides if quality or scanning.
2. Next choice is film speed.
As with everything else in life, choosing the film speed is an exercise in compromise. Slower film speeds (smaller ISO) have a finer grain but the greater light required means slower shutter speeds and could interfere with picture taking. Faster film speeds allow for faster shutter speeds but the increased grain size can be distracting.
ISO 100 or slower for the finest grain. Use in good lighting conditions such as bright sunny days.
ISO 200 is a good general purpose film for slower lenses such as those found on compact cameras or zoom lenses. In print film this speed has all but replaced ISO 100 as the quality of modern films have grain comparable or better than last year's ISO 100.
ISO 400. Where you require faster shutter speeds for action shots or in medium to low lighting conditions. Grain is getting noticeable at this speed.
ISO 1000 or faster. Use in low lighting conditions such as indoors and at dusk. Grain is quite noticeable. One can exploit this resulting in grainy, gritty photographs.
STORING FILM
As film ages its colour changes. This colour cast is subtle but noticeable. For example, a brand new film fresh from the factory might have a slight red colours cast where the same film (and same batch) that has sat on a shop's shelf for a year might have a slight green cast. At some point in its age the film will have an optimum colour balance where the colour cast is a minimum.
For print film this effect can usually be ignored as the photo labs' printing machines will automatically compensate for this cast and produce acceptable prints (though probably inaccurate). Slide film is more sensitive due to fact that you view the film itself not prints.
The manufacturer knows this and will endeavour to have the film shipped and on the shelves when it is almost at optimum so that is optimum (or near-optimum) for the time it is expected to be on the shelves. Think of fruit in the grocers. The new bananas arrive slightly green and ripen on the shelves.
Manufacturers also make professional film. This is the same as the non-pro film (though often it actually is better quality) but has been allowed to age at the manufacturers to optimum colour balance. The extra cost for pro film assures this. Some camera shops and photo labs have a fridge containing professional slide film - keeping the film cool slows this aging process. Storing film in your own fridge helps to keep it fresh if storing for a period or in hot climates. Keep them in their containers.
You should get films processed as soon as possible after exposure as the latent image will begin fading.
Films beyond expiry dates can still be used but you should exercise caution. Do not use them for anything important. As well as the aforementioned colour cast, which might be significant, the film can dry out and crack. The result is prints that look like crazy paving! (I've had this experience with an old black and white film). Buy film as you need it. Extreme temperatures and moisture can really make the film suffer, store them in a cool dry place. Keep out of the sun, stuffy cars and away from radiators.
Always use the container supplied, this keeps dust and dirt out and spoiling your film.
FILM BRANDS AND QUALITY
As with everything else in life, typically you get what you pay for. Big brands like Kodak and Fuji make very good films and you'll pay a bit more than lesser brands for the better quality. Ilford makes some excellent black and white films.
Kodachrome is number one for film archival. It's longevity is second to none.
Kodak colour films typically are strongest in the red/yellow part of the spectrum. Rendering of reds, yellows and skin tones look great. Fuji films traditionally are strongest in the green part of the spectrum. Great for nature and landscapes. Velvia 50 is superb, now discontinued, replaced by Velvia 100.
DX FILM SETTING
On most rolls of 35mm film there is a pattern that looks something similar to a barcode. This is the film speed coded on the canister. It allows cameras that support DX coded canisters to automatically set the film speed. Very useful if you often use different speed film and forget to reset the film speed. It also simplifies compact cameras to the point where they don't allow manual setting of film speed.
A LITTLE HISTORY
Many, many years ago two film speed designation systems competed to be the standard. One was defined by the DIN standards body the other by ASA standards body.
The DIN system is an additive scale where each stop of film speed alters the DIN number by three. So to increase the exposure by one stop subtract three to the DIN film speed setting and to decrease the exposure by one stop add three. Each one of the DIN scale effectively being one third of a stop.
The ASA system uses a multiplicative scale where one stop doubles or halves the ASA number. To increase the exposure by one stop half the ASA film speed setting and to decrease the exposure by one stop double it.
The DIN system simplifies exposure compensation settings but the ASA system is more akin to the way the rest of the camera works (ie shutter speed doubles or halves per stop) and ultimately chosen for the ISO standard.
You will still find both settings on the outside of film boxes. It will say something like ISO 50/18
Example ISO/DIN equivalents:
ASA/ISO == DIN
25 == 15,
50 == 18,
100 == 21,
200 == 24.
Danny Hartley is a photographer and moderator at: http://www.ImagesClub.com