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Differences between digital and film photography (10/12/2003)
By Tom Hirsch
Probably (no, definitely) the greatest difference between film and digital photography is the image-storing sensors. In film photography, photos are recorded on tiny particles of grain imbedded in the film emulsion. In digital photography, though, images are stored in the form of tiny pixels (picture elements) on a magnetic sensor. The sensor might be any one of a number of devices, depending on the camera manufacturer. Memory mechanisms go by such names as CompactFlash Card, SmartMedia Card and Memory Stick. Some digital cameras use a small compact disk (CD) as a storage device. Even standard 3-1/2 inch floppy disks are used in some digital cameras. A floppy is limited to much fewer images than the others, but these disks are cheap so you could use a number of them on one outing.

Digital cameras are usually rated by the number of pixels they use to make the highest quality single image. The camera's rating is given in megapixels (1 megapixel is 1 million pixels). Today's digital cameras range from less than 1 to 7 or more megapixels. Depending on the quality of the camera, a 2 megapixel image could make a good 5 X 7 enlargement, and a fairly decent 8 X 10. Many 4 to 7 megapixel cameras can produce 11 X 14 inch photos that rival those made from film.

Unlike film cameras, most digital cameras offer a range of quality settings. JPEG (Joint Photographic Experts Group, if you really must know) is the most commonly used setting for digital images. Pictures taken in the JPEG format occupy the least amount of pixel room on an image sensor card so you can store more images. When a picture is taken in the JPEG mode, it's compressed by having pixels proportionally removed from the image. Most digital cameras provide a range of JPEG settings so you can select the amount of compression you're willing to accept. The highest setting will give the least amount of loss, and could produce an image almost equivalent to that obtained from a completely uncompressed image file.

But degree of compression is relative. For example, if you were to select the middle JPEG setting on a 2 megapixel camera, you might be able to get by with a 4 X 5 print. With a 5 megapixel camera, the middle setting would still be good enough to get a high quality 5 X 7 or a pretty decent 8 X 10.

With all digital cameras, the lowest JPEG setting will result in the greatest amount of compression. This setting is appropriate, and really the most desirable, if you'll only be viewing the images on a computer screen, or sending them by e-mail over the Internet.

TIFF (Tagged Image File Format) or RAW (no acronym, that's just what it's called) are uncompressed formats available on many digital cameras. Images taken in either of these modes are much larger than JPEG files and occupy more space on an image sensor. They also take much too much time to download over the Internet via e-mail. Use the greatest JPEG compression for this, and reserve TIFF or RAW files for your serious, best quality stuff - pictures you might want to display on your walls.

TIFF and RAW are somewhat different, but the differences are negligible. At this point, they can be considered equivalent. They will both provide the best images.

But what if you take a picture at the greatest JPEG compression ratio, and later decide to display the image on the wall as an 8 X 10 print? Good question. You'll have the image, but it could have been a much better photo if it had been taken at a less compressed JPEG setting or in the TIFF or RAW mode, if available.

For greater flexibility, you could shoot everything at the highest quality setting, whether JPEG, TIFF or RAW, and save it that way on a disk or in the computer. Later, in the computer, you could downsize a copy of the image to one of the compressed JPEG modes if necessary or desired. That would give you a best-quality image that could be used later on in any way that you'd like. 


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