File Formats Made Easy

When an image is captured by your camera's digital sensor, a series of settings are applied as alterations to the original raw data. In many high-end cameras, this raw data can be retrieved "un-touched" as a RAW file, but most digital cameras save your photos as JPEGs. In addition to "alterations" for sharpness, white-balance, and the rest (which are either selected by the camera's default settings or set by you), the choice of file format that the image is saved in can have a profound affect on overall quality. Get it wrong, and there's little that can be done even in Photoshop.

So how do choose a file format? It's easier than you think. Here's a look at the formats, and when you should use—and not use—each.

All JPEGs Are Not Created Equal
Strictly speaking, JPEG isn't a file format, but an image-compression standard (originally developed by the Joint Photographic Experts Group, hence the name). Most JPEGs produced by cameras are JFIF (JPEG File Interchange Format) and EXIF (EXchangeable Image File) compliant, which allows both image data and camera settings to be exchanged between hardware and software. This EXIF data is the information that's displayed alongside our shots in image browsers and editors. This data also permits compatible inkjet printers to make pretty good quality prints, even without a PC.

Since JPEGS are such an efficient way to store and transfer data, they're the most popular way to e-mail images. They're also easily processed in-camera. That is, JPEGs typically move quickly from the buffer to the memory card. This also speeds up how quickly the images appear on the camera's LCD. Want a fast burst mode? Shoot JPEGs. And since JPEGs are compressed files, they don't take up a lot of space on the card. Want the most shots per memory card? Shoot JPEGs.

The downside of JPEGs is that they use "lossy" compression. That is, data is lost during the process. While color space and metadata, including EXIF camera settings, are preserved, much of the discarded data relates to image color. When you open the file and it's decompressed, much of the original information is recovered through clever algorithms. Although efficient, it's still incomplete, and the photos can show degradation. The higher the compression applied, the greater loss of data, leading to washed-out colors and a loss of fine detail, as well as so-called artefacts-- speckled, mosaic-looking, blocks of color.

To limit this degradation, use the camera's higher quality settings. But it's a trade-off--less compression means larger files. Many cameras offer at least two such "quality" settings, typically described along the lines of "Good,", "Better," and "Best," they nearly always refer to JPEGs. Chances are, you'll also see setting for file formats, such as TIFF or RAW.

If you're planning some editing in Photoshop, and still want to get as many shots as possible on your memory card, go with the "Best"-quality JPEG setting. But each time any alterations or enhancements are saved, the compression process is applied. So to prevent further loss during editing, make a copy of your original JPEG as a TIFF, or native file format of your editor, and work on that.

Don't plan to do any editing, cropping or enhancing? Select "Better," or its equivalent. What if you have little space left on your memory card, and you need to keep shooting? Drop down to "Good," but don't lower the pixel count (such as switching from 6MP to 3MP), since higher resolution files stand up better to the degradation that accompanies compression.