Part 1 of this series noted the distinction between “backing up” images to keep them safe from inadvertent data loss and “archiving” images for years. When selecting images for your permanent archives, you must also choose the best file format in which to store them. You need a format that is likely to be accessible by digital devices of the future and contains as much data as possible about the colors and details in your image.
The array for file-format options sounds like alphabet soup: JPEG, TIFF, RAW, PSD, and DNG. These acronyms generally refer to the file suffix (*.xyz, for example), but they also refer to the file type and its inherent characteristics.
Personally, I always keep 90 to 95 percent of my original files in permanent storage. (The only ones not included are those that are obviously unusable.) I typically store my finished (or “optimized”) master files as TIFFs. As you learn more about the alternative file types, you’ll understand why.
RAW files are typically generated by digital cameras or scanners. These files consist of data captured by the sensor used in the imaging device (camera or scanner). Because these files have had very little processing, they are not yet really pictures. For general viewing, these files need to first be processed or edited in a software application.
Although keeping RAW files is important if you want to experiment with processing or outputting your image in different ways, some believe these files may not be ideal for archiving—especially if it’s the only file format you plan to store. Adobe makes a valid argument that most RAW files are created in a format that is proprietary to your camera manufacturer. What if that manufacturer decides to leave the camera-manufacturing business for some reason? For quite some time, Adobe has tried to persuade camera manufacturers to adopt its DNG RAW file format as a standard (much like “digital negatives” of film). But so far, there have been only a few takers.
JPEG files are everywhere because many consumer-level and mid-level cameras only give you access to JPEG-format images. JPEGs are great if used appropriately, but they’re not ideal for storage for serious photographers.
For example, JPEG files are useful for email and web uploads because they are always compressed to save space. But this compression always results in the irretrievable loss of some of information in the image – even when you choose the lowest level of compression when saving your image as a JPEG.
Furthermore, if you plan to edit a JPEG file over multiple sessions, the image will degrade in quality with each open and resave cycle. Noticeable artifacts will appear.
There are other reasons not to use JPEGs for archiving your images.
JPEG files are normally saved in a relatively small color space, such as sRGB. This limits the range of colors that will be available for image reproduction on current and future output devices (e.g. displays, printers, digital signage, tablets, etc.)
Fig. 1 below compares the relative size of sRGB to another commonly used color space, Adobe 98 RGB.
Although some cameras will create a JPEG file for you in Adobe 98 RGB, there are other shortcomings to consider. For instance, JPEG files cannot be saved in high-bit format. They also cannot be saved from image editing software such as Photoshop with embedded options such as layers or clipping paths.
PSDs (Photoshop files)
Speaking of Photoshop, you could use the PSD files generated by Photoshop for archiving your images. But remember: Adobe is constantly upgrading its software. In fact, PSD files created with newer versions of Photoshop may not be accessible using older versions of the software. So be careful.
Personally, I choose to archive almost all of my images as TIFFs. TIFFs are very widely supported by image editing software and are nearly as ubiquitous as JPEGs. The TIFF format was originally developed in an attempt to standardize output from digital scanning equipment. However, they are not compressed and are usually used with a larger color space such as Adobe 98 RGB or ProPhoto RGB.
Given their wide compatibility, lossless storage, and use across many software platforms, TIFFs are quite useful for photographers and can easily be used for multiple edits or for archiving.
Any Other Questions or Ideas?
I wrote this series of posts to respond to some of the storage and archiving questions I hear most often when I give photography seminars. If you have any other questions (or strategies and tactics for backing up, archiving, and storing images that you would like to share), send them my way.