Film:

Choosing a proper film is a central part of underwater photography. Poor film in an excellent camera will give lousy pictures, whereas good film in a cheap camera will let the photographer take his/her camera to the edge of its capabilities. Picking a film can be a real challenge - there are several sizes, speed, and types of film. Luckily, there are only a few key features you need to consider.

Film Speed: The main concern for the underwater photographer is film speed (sensitivity). Film speed is described as "ISO", with higher ISO numbers representing faster film. Faster film (i.e. ISO1200) needs less light then lower speed films (ISO100) to take a picture. The downside to the higher speed films is that these pictures can look grainy. Generally speaking divers want moderate speed film (ISO400-800), as this allows the film to make maximum use of the limited light found underwater, without suffering from excessive graininess. Even digital camera's have ISO ratings. Like film cameras, higher ISO tends to lead to grainy pictures (noisy pictures in digital lingo). However, digital camera's are a little more lenient when it comes to ISO, so a digital camera capable of only ISO100 will still probably take good photo's. If your camera can use a range of film speeds underwater try and go with a slower (i.e. lower ISO) rated film - you'll get better quality pictures. But if you find that your pictures are always dark, or lack vibrancy in the colours, move to a faster film.

Colour: Another important aspect of film is it's ability to see colour. Water absorbs different colours of light more efficiently (more on this in the Light Characteristics section), so it is important to pick a film highly sensitive to colour. So-called "vivid colour" films are your best bet. Often slide film provides the best colour reproduction, although it can be more expensive to make prints (or you have to take a slide projector everywhere you go).

Other Characteristics: There are other characteristics you need to take into account. One is film format (i.e. size). Standard film is 35mm in size, and is the most common size you will find. Most people prefer this film, and in many cases this type of film is the only one carried in stores. This film comes in rolls of 12, 24 or 36 exposures. We'd recommend that you use 24 or 36 exposures. Any less and you may run out of film right after you run into a prized subject. Other film types include 110mm, or medium-format (MF film). MF format is a high-quality (and physically larger) film orientated towards expert photographers, and is too expensive for 99% of normal people. 110mm format film is used in many cheap, low-end cameras. It tends to have low resolution, and is not suitable for underwater photography.

General Advice: If using a film camera it is a good idea to pick one or two types of film and stick with them. Learn the characteristics of you chosen film - in the end you'll know exactly what the film can and can't do - and as such you'll be able to make the most of the film.

Digital "Film":
When talking about digital camera's the term "film" actually describes two components of the camera. One is the media you store the images on, the second is the CCD in the camera which actually takes the picture.

Media: Digital media is what you use to store pictures from a digital camera. There are several types of media, although most camera's will only take one. The most common is known as "Compact Flash" (CF) media, and is used by many camera manufacturers (Canon, Nikon and many others). Another common format is known as SD media. There is no real difference between media types, but in general you want to buy the card with the largest capacity. The more a card holds the more pictures you can take, and you'll have to dump your pictures to a computer less often.

CCD: This is what manufacturers are referring to when they say a camera has x megapixels. So a 3-megapixel camera has a CCD with 3-million image sensors. Generally speaking, you want to buy a camera with as many megapixels as possible, although for the average user there in no point in buying a camera with more then four or five megapixels of resolution. If you take pictures with a 4 to 5 megapixel camera you can print them out at upto 8.5"x11" in size without ending up with a grainy picture. So unless you want to print posters there really isn't any point in buying a higher resolution camera.

One thing to keep in mind when using a digital camera is that you should always save the pictures in the highest-quality size/format you camera is capable of. Although this means you can fit fewer pictures onto your media card, your pictures will be of the best quality possible. After all, what's the point in putting our the money for a high-end camera if you aren't going to take advantage of it's resolution?


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