Understanding digital image files

A digital file is a grouping of related binary data( 0s & 1s) that represent words, graphics or photographs. If we looked at the code it would have little meaning - it would just be a continuous string of 0s and 1s. The image on the left is a composite from the Adze to Coda series where I used the numbers overlaid with photograms to represent the idea of binary tools.

Different file formats

In digital photographs, the data can be arranged in different formats that allows us to access, store, enhance or manipulate the data, and also transfer the recorded data. In a digital camera this series of numbers takes the place of film, when we work on the file in photoshop or another image enhancement or manipulation software, we could compare it to doing a series of work prints.

Digital Camera - File formats

The most commonly used format, JPEG, is often the only one available on entry-level and some intermediate digicams. Not to worry, this format is perfectly fine for the vast majority of digital camera users.

Many higher-end digital cameras let you select between JPEG, TIFF and RAW. Professional photographers and serious photo-enthusiasts usually prefer to shot RAW.

Some advanced cameras have a setting to simultaneously shoot RAW + JPEG. Both formats will be saved to a memory card as separate files.

There are three types of digital camera file formats:

JPEG

JPEG, pronounced jay-peg, is an acronym that stands for the group that developed the file type, the Joint Photographic Expert Group. JPEG is a method of compression which significantly reduces the file size of photographic and other continuous tone images. An image in JPEG format has a .jpg extension: filename.jpg.

Digital cameras offer several JPEG compression levels and quality settings. For images with the least compression, the loss of quality is usually not seen by the human eye. Keeping jpeg compression to a minimum is a must if you want to print quality photos.

Some digital cameras only offer the jpeg file format. Advanced digital and Single Lens reflex cameras offer the option of shooting two additional file formats, TIFF and RAW.

JPEG files, unlike TIFF and RAW files, do not take up as much room on a memory card. They are also processed faster by the camera than the other file formats.

JPEGs store important camera settings and scene information known as EXIF data.

TIFF

TIFF (Tagged Image File Format) files don't lose image file information in the compression process. They do, however, take up a more space on a memory card compared to a JPEG. A tiff file also takes longer time to write to the card.

TIFF compression reduces images to about one-third their original size.

For example, a single TIFF image file shot at 5 MP (megapixels) is over 14 megabytes. By comparison, the same photo taken as a Fine Quality JPEG is just over two megabytes. At Normal JPEG setting, a 5 MP shot produces only a 95 KB (kilobyte) file!

Like JPEGs, EXIF information is embedded in original TIFF files.

An image file in this format has a .tif extension, eg. filename.tif.

RAW file format

A RAW image file is often referred to as a true digital negative. The option to shoot RAW is available on many advanced and professional digital cameras. Images in this format have a .raw extension, eg: filename.raw.

There is much more latitude controlling exposure than with JPEG files. When shooting RAW, no processing is done in the camera to the file. As a result, the photographer has total control adjusting elements, such as sharpening or white balance, when editing a RAW file.

When processing a RAW image, no changes are made to the actual file. A separate file is created and all adjustments are kept in the associated file.

The RAW format, considered essential by professional and serious photographers, is still not widely used by others. At this time, RAW files can not be opened with every image editor and can take longer to process when editing.

A RAW image has a smaller file size than a TIFF but is considerably larger than a JPEG.

But my digital camera doesn't shoot RAW!?!

If you're concerned because your camera doesn't shoot RAW, don't worry. Many digital camera users find JPEGs, when shot at the highest resolution and lowest compression settings, meet their expectations for image quality. Many also find JPEGs easier to edit than RAW images.

Some digital cameras have an option to take both RAW and JPEG images at the same time (JPEG + RAW setting).

EXIF

Digital cameras save JPEG (.jpg) files with EXIF (Exchangeable Image File) data. Camera settings and scene information are recorded by the camera into the image file.

Examples of stored information are shutter speed, date and time, focal length, exposure compensation, metering pattern and if a flash was used.

Use EXIF as a learning tool

Many camera owners study EXIF to compare successful photos to those that are not. Data provides insight about how camera settings affect photo characteristics such as exposure, depth-of-field and subject movement.

EXIF is read by applications that support JPEGs. They include web browsers, image editing and organizing programs and some printer drivers. The printer drivers use the information to automatically enhance images, which can result in a better looking prints.

Preserving EXIF information

If an edited image is saved correctly to preserve EXIF data, the information can be viewed online at photo hosting sites. Some photo hosting sites, such as Flickr, use the word "properties" instead of EXIF.