Main Digital Photography Formats
Digital cameras use three formats of still photo files, JPEG, TIFF, and RAW. Not all cameras will offer all of these file types. For example, RAW files are generally only available on expensive still cameras or DSLRs. JPEG may be the only type of file that a particular camera uses, especially a low-end model.
JPEG (acronym for Joint Photographic Experts Group, though sometimes written JPG like the file extension) is by far the most common type of picture file you will come across. It is a universal format that can be read by PC and Mac computers, can be viewed on the Internet, and can be used by other devices such as cell phones. Yet JPEG is a very sophisticated format with many options, some of which can be quite confusing. To get the best quality JPEG images or to understand how to store photos properly in your camera's memory, you must understand how JPEG works. JPEG is quite different from the other two common camera formats, TIFF and RAW:
First, it allows considerable compression. This means that the size of a file can be shrunk so that you can save many more pictures on your memory card or your in-camera memory.
Second, the compression method that JPEG uses loses some picture data. Because of this, JPEG has what is known as lossy compression.
The picture quality setting (or a setting with a similar name) in your camera can be quite confusing. The problem has to do with understanding the distinction between size of the image and the amount of JPEG compression.
First, you must choose the image size. The resolution setting in your camera refers to the size of the image, the pixel count. It is often listed in pixel dimensions such as 640×480 or 1600×1200. These numbers refer to the width and height of the image in pixels. The bigger the dimensions, the better the resolution.
Next, you often have to choose the amount of the compression. Typically there are three quality settings, such as basic, normal, and fine. The higher the compression, the lower the quality, but the more images you can fit in your camera's memory. The lower the compression, the higher the quality and the fewer you can fit into your camera's memory.
TIFF (Tagged Image File Format) allows you to store high-quality images in an optional lossless compression format known as LZW (named after its developers, Lempel, Ziv, and Welch). The TIFF format supports 8-bit gray-scale and 24-bit color images. In addition, it accommodates 1-bit black and white, 8-bit color, and numerous other color settings. Consider using TIFF if you plan to edit your images repeatedly, use them in a publishing software program, or produce high-contrast photos. The TIFF format is compatible with both Windows and Macintosh and is widely used in desktop publishing.
Although TIFF files can be compressed in a lossless fashion, the reduction in file size is not very large. TIFF is not compatible with Web browsers and therefore should not be used on an Internet Web site. While you can send one as an e-mail attachment, the recipient of your attachment may need a separate program to view the file.
TIFF files are in between JPEG files and RAW files. They are much larger than JPEG files, for example, and smaller than RAW files. With TIFF no data gets lost, yet they retain almost as much information as a RAW file.
If you want a full resolution image with almost total control over its look plus a universal format that is recognized by most photo editing programs, TIFF is the way to go. However, TIFF files will fill up your camera quickly and they will take longer to download than JPEGs.
The term
Professional photographers like the RAW format as it gives them complete control over the final image. Specifically, the RAW format allows more control over white balance, color depth, color saturation, sharpening, and contrast. It has a greater tonal range than a JPEG picture, for example.
However, working with RAW files is not simple. Because they are quite large and uncompressed, they can fill up the camera's memory quickly and also slow down the frame rate of the camera — that is, the lag time between taking sequential pictures. In the computer they will require a lot of RAM and also take a good deal of time to work with. In addition, they will need to be converted into a standard file format with a converter (usually supplied by the manufacturer), since the format is not standard.
Some newer cameras save a picture in two formats at the same time: the JPEG and the RAW format. This option gives the photographer more wiggle room. If the JPEG file does not meet the photographer's standards, she can go back to the RAW file for fine tuning.
Digital Negative (DNG) is a file format developed by Adobe to create a standard way of saving, viewing, and processing RAW files. RAW files are converted to the DNG format using Adobe's free DNG converter. The converter works with Windows and Macintosh. More than 150 cameras and their RAW file formats are supported. Adobe's well-respected Photoshop and all other Adobe photo software supports this format.
While this standard has not yet been widely adopted, the odds are good that it will become a de facto standard. This is because Adobe, the leader in photo-editing software, is pushing its use and making it freely available. To find out more about DNG and to download the free converter, go to
Adobe calls its format “digital negative” because the RAW format, although positive, is like a film negative in that it gives the photographer the greatest possible flexibility. Adobe has made the DNG format available to all software developers (not just Adobe), so that they can add DNG capabilities to their photo editing programs.
EXIF (exchangeable image file format) is not really a file format but a standard that allows considerable information about the camera settings to be saved along with the picture. It is used primarily with JPEG files but also works with TIFF files. JPEG files that use EXIF are considered EXIF compliant and cameras sometimes list the JPEG format as JPEG (EXIF) or as JPEG (EXIF version 2.2). For learning and diagnostic purposes, this kind of information is invaluable. It also means that you can probably put away that notepad for recording such information and concentrate on shooting.
Digital cameras that use EXIF can record such exposure settings as:
The camera-assigned file name
The camera make and model
Date and time of shot
Shooting mode
Shutter speed
Aperture
Focal length
Image size
Type of metering
Exposure compensation
ISO
This extra information is known as metadata, and this list is only a sample of the information that a camera might save. Some cameras may save different data; it depends on the camera. After downloading your images, you may need a special EXIF extractor in order to view the metadata that was captured by your digicam. If your camera did not come with software allowing you to view the metadata, there are several programs you can get for free or buy for this purpose. For example, some free software can extract the EXIF information and save it as text or as CSV files, creating an easy-to-read permanent record of your picture-taking settings. Also, many image editing and processing programs such as ACDSee can display this data.
While the ability to record all the camera settings is quite useful, there are a number of problems with EXIF files and at the moment they have not been solved. Some image editors strip the metadata when saving and other editors cannot read the metadata properly and corrupt the data. Be careful saving EXIF-compliant files, as the information can get lost if it is not saved properly. Read the instructions in your picture file management program.
For more about the EXIF standard, visit a good unofficial EXIF Web site at
EXIF focal length information will often be stated in the true focal length of the digital camera lens and not the 35 mm equivalent. This means that you will need to understand the relationship between the actual focal length of your digital camera, which varies from digital camera to digital camera, and the 35 mm equivalent.
