File Formats - In the Camera

Two basic file format options are available to you when working with a digital camera to capture still images. Each has its strengths and weaknesses, and each can impact the final image quality.

RAW capture

     The RAW file format is not a file format in the traditional sense. In fact, RAW is not an acronym. It is capitalized only to resemble the other file formats. Rather than being a single file format, RAW is a general term for the various formats used to store the raw data recorded by the sensor on a digital camera. Each camera manufacturer has developed proprietary file formats for RAW capture modes. Because none of the proprietary file formats are standard image file formats, you must convert RAW files before you can edit the image.
    You can convert RAW images to a file you can work with in Photoshop or print by using the camera manufacturer’s software or as we recommend and practice by using Adobe Camera Raw or Adobe Photoshop Lightroom. Multiple RAW file formats are created by many camera manufacturers, and often new versions are included with each new camera model release. As a result, literally hundreds of RAW file formats exist. Adobe has responded to this by providing an open industry standard for RAW capture called the DNG (digital negative) file format. DNG has been adopted by several digital camera manufacturers but hasn’t managed to stem the tide of new RAW file formats. You can convert proprietary RAW captures into the DNG file format to ensure compatibility well into the future with the free Adobe DNG converter, Adobe Bridge, or Adobe Lightroom.
     The file size, in megabytes, of RAW captures for most cameras is approximately the same as the megapixel count of the camera. There is some variation in this from camera to camera, and some formats offer the option to further compress the data. Regardless, the files that result from RAW capture will be considerably larger than JPEG captures but smaller than never used or recommended TIFF captures. The advantages of the RAW format include the ability to capture high-bit data; no in-camera processing; and options for adjusting the exposure, white balance, and other settings with great flexibility during the conversion process. The disadvantages are the relatively large file sizes, files that must be converted before you can retouch, composite, or post them on the Web, and the need to work with high-bit files to obtain all the benefits of the highbit capture. We highly recommend RAW capture and use it for the vast majority of our photography. The tools for working with RAW captures have become sophisticated enough that there are no longer many strong arguments against RAW capture. We very much want to maintain the benefits of high-bit data, post-processing flexibility, and lack of lossy image compression that are among the benefits of RAW capture.


JPEG 

    The major advantage of the JPEG (Joint Photographic Expert Group) format is convenience. Just about any software application that allows you to work with image files supports JPEG images. Also, the files are small because compression is applied to the image when it’s stored as a JPEG. This compression is lossy, meaning pixel values are averaged out in the process and the image will lose detail and color, if you use the highest quality (lowest compression) settings, image quality is generally still very good. But again we don’t use the JPEG file format when image quality is the most important final criteria. Admittedly, we do use JPEG for quick party pictures or snapshots that are only destined for eBay or Facebook display and also when capturing multiframes for stop motion and time-lapse projects .
    When selecting the JPEG format in the camera, you will generally have the option of size and quality settings. We always recommend capturing the most pixels possible, taking advantage of the full resolution of the image sensor in your camera. This size option is generally labeled Large, and we recommend using the highest possible quality setting.