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Digital cameras & housings by Brian Pitkin April 2003 There are hundreds of different makes and models of digital camera on the market and a new model seems to appear almost weekly (see Digital Photography Review for news, reviews etc). Not all of the available digital cameras have a suitable underwater housing, so those discussed in this article include only digital cameras for which housings are available in the UK at the time of writing. Although ewa-marine make an extensive range of flexible housings, for both still and video cameras, these are not suitable for diving below about 5 metres, so they have also been ommitted.
Why digital? Immediacy: Most digital cameras offer you the ability to review your pictures and delete those you do not like, even underwater with some models. In addition, immediately after your dive, once dry, you can connect the camera (or memory card) to a computer (or television) and re-live the dive along with your diving buddies, family and friends. You do not have to wait for the images to be processed, as is the case with film. Low light: Most digital cameras can be used to take pictures in low light level conditions and, if the camera includes the facility to control white-balance, you can even take reasonable colour photographs in relatively low light conditions, something which cannot be acheived with film. As a bonus, images captured without artificial light do not generally suffer backscatter, so they will look sharper. Manipulation: Once you have captured an image digitally you can manipulate it to improve the colour balance, birghtness and contrast. You can crop the image, invert the image, combine images. The list of possibilites is limited only by your imagination and the availability of suitable computer software such as Adobe Photoshop or Paintshop Pro. Copying: Once downloaded to your computer you can print multiple copies, you can make copies on floppy disc, CD-ROM or DVD, and attach copies to emails to anyone, anywhere in the world. The choice There are essentially three different types of digital camera - compact, compact zoom and SLR (single lens reflex). Compact and compact zoom digital cameras, as their name implies, are compact and some, suitably housed, can be carried in the pocket of your BC (buoyancy compensator). Most of the earlier, low resolution compact cameras are no longer available, although suitable housings can still be purchased for some. Both compact and compact zoom cameras have a fixed lens, which cannot be changed. However, close-up lenses are available for some compact zoom cameras. Compact zoom digital cameras, such as the Olympus Camedia C-4040 Zoom (above, centre), have the advantage over compact digital cameras (above, left) in having a lens which can be zoomed out or in to increase or decrease the size of the subject area, typically from the equivalent of a standard 35 mm lens to that of a 70-80 mm lens. Zooming the optical lens does not reduce the number of effective pixels used to capture the image. However, digitally zooming the lens does. Many of the earlier, lower resolution compact zoom cameras are no longer available, although suitable housing can still be purchased for some . The trend with compact zoom cameras has been towards higher resolution and greater optical and digital magnification. SLR digital cameras, such as the Nikon D100 (above right), have the further advantage over both compact and compact zoom cameras in that the standard lens can be changed for another, wide-angle, zoom or macro lens by the same manufacturer or one that makes compatible lenses. So, if you already own a SLR film camera and a range of lenses it makes sense to consider an SLR digital camera by the same manufacturer, but you will need to purchase a new housing (and possibly domes) to use it underwater.
Resolution If you want to be able to print your digital images at A4 or larger or want to project them on a large screen using a digital projector, then resolution should be your guiding principle. Resolution is typically quoted as either the number of pixels across an image by the number of pixels down, e.g. 1600x1200, or millions of pixels (megapixels) and effective millions of pixels (megapixels). The total number of pixels in the camera's sensor array or the charge coupled device (CCD) as it is known, may exceed the effective number of pixels - the number that are actually used to capture the image. Not all manufacturers state the effective number of megapixels, which can be misleading. If you bear in mind that 50 ASA 35 mm film is roughly equivalent to 30 million pixels (or 30 megapixels), it soon becomes evident that in order to achieve images of a similar quality to film, you need a digital camera capable of capturing images at that resolution. Unfortunately, there is no affordable digital camera currently on the market which can capture images at anywhere near this 30 million pixels. So a compromise must be made! Typically the available digital cameras have from about 1 million pixels (megapixel) up to 6 million pixels (megapixels). The greater the number, the higher the resolution and usually the higher the price!
If you only want images to display on your computer or television screen, either immediately after a dive or back at home, then a digital camera with 3-4 megapixels will probably be sufficient for your needs. Remember, apart from purchasing a greater capacity memory or flash card than is supplied as standard and perhaps the leads to connect to your computer/television, there are fewer additional expenses, if you already own a computer or television. The ease which you can capture images (and delete those you don't like) will undoubtedly encourage you to purchase a digital camera with greater resolution in the future! |
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