Why use RAW files like NEF, CR2 Instead of JPG?
What is the Best File Format for a Compact Digital Camera or a DSLR?
Jul 9, 2009
Point-and-shoot compact cameras usually save images in JPG files. (also called JPEG). Digital single lens reflex cameras and high-end compact cameras can also save images as RAW files. Canon, Nikon, Sony, Sigma, Panasonic, Olympus and Pentax all make cameras that can save RAW files. The RAW files have different file suffixes like CR2, NEF, X3F depending on the camera manufacturer.
The difference between JPG and RAW is that the JPG is compressed to save space on the memory card, but the RAW file holds all the information from the sensor. Compare how the two formats work to decide which is better to use:
How JPG s Work
The data from the camera sensor is processed by a mathematical formula devised by the Joint Photographic Experts Group. The sensor contains 10, 12 or more million pixels, each sending a numerical message to record either brightness or red, blue or green colour. That's a lot of data. Compression reduces the amount of data. An outline idea of the process:
- information that is less important to the human eye is discarded
- the data is grouped in 8 by 8 pixel areas
- colour and brightness are recorded for these pixel areas
The result is a much smaller file size. As well as doing JPG compression, the camera applies settings like white balance, saturation and sharpening. These can be set by the user. For instance, if shooting under incandescent light, choosing the correct white balance setting produces natural pictures without a yellow colour cast. Shooting flowers or landscape, the user can increase saturation for a more vivid effect.
A disadvantage is that if the photographer wants to make further corrections on a computer, the image gets degraded every time it is opened, altered, and re-compressed. Square marks due to the pixel grouping can appear.
How RAW Files Work
The colour or brightness data from each pixel is saved onto the memory card. No data is lost but fewer images fit onto the card, and each shot takes longer to save.
For instance, a Canon G9 takes 4000 x 3000 pixel images. With a 4Gb card it takes 1250 high quality JPGs, but only 190 images saved as RAW files.
The advantage of the RAW format is that when it is opened on a computer, the photographer can make changes to the settings for exposure, white balance and saturation, which would not be possible on a JPG without downgrading the image quality. Software may allow more complex adjustments, like correcting barrel or pincushion distortion from the lens, or selectively lightening the darker areas of an image.
RAW Means More Computer Time
JPGS are a universal format and can be downloaded straight to a printer, viewed on a computer, emailed to friends or posted on websites. RAW files are more labour intensive.
RAW files can't be used for printing straight off the camera. They have to be downloaded onto a computer. It reads the pixel data and displays the image. Different camera makers have slightly different way of encoding the pixel data. It has to be read with their software, usually supplied with the camera. Image processing programs like Adobe Photoshop can have a plug-in from the camera manufacturer to read the raw file.
Once the image is corrected, it can be saved as a TIFF which is a standard format that preserves the pixel data. It can be corrected again without problems if it is saved as a TIFF. Or, to save disc space, it can be saved as a high quality JPG if no more correction is needed.
The Trade-off between Quality, Time and Hard Disc Space
The photographer using RAW files has greater creative control to optimize images. Retouching to remove litter from a landscape or lines from a face is better starting from RAW. Less experienced photographers may appreciate the ability to correct exposure and white balance after the event.
Professional photographers may save time and hard disc space by shooting high quality JPG. Wedding photographers often use JPG as they are working in a controlled environment where lighting and white balance are predictable. They gain faster workflow and less hardware costs.
Choosing a compact camera or DSLR
The latest digital compacts take great pictures, even in economy price brackets. Camera choice depends on how it is to be used. For instant printing without involving a computer, or for display in a digital photo frame, or posting on a website, a camera that just shoots JPG files will fit the bill.
On the other hand, cameras that have the option to shoot RAW or JPG are becoming increasingly affordable. Then the photographer can set the camera to RAW for maximum creative control, or JPG for speed and convenience.
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