Most people shooting digital pictures today are probably using their camera's standard image file format, when tends to be JPEG images. These are digital picture files which have compressed the actual image data into a smaller file size, but for most consumers will work well enough.
Alternative Format may be Available
In higher-end digicams and DSLR cameras there is an alternative, namely: the camera's RAW image format. This format is the data from the image sensor with very little in-camera processing. Of course, there are advantages and disadvantages to both formats of image files.
Benefits of JPEG Image Files
The main advantage of this format are that it not only saves you lots of storage space on your camera's memory card as well as your computer's hard drive, but it is also very compatible with nearly any image viewer that can be found. Of course, there are trade-offs for the photo-enthusiast interested in using this format.
What JPEG Loses in the Translation from the Image Sensor
The biggest trade-off is that the compression scheme throws out lots of bits of information in order to get the image's file size smaller. Now, throwing out bits isn't necessarily bad, but the algorithms used by the JPEG format do this in such a way that the information it tosses is truly lost and unrecoverable.
In general, for the web, 4x6, or sometimes even 8x10 prints of properly exposed pictures, the in-camera JPEG images should be fine. But the loss of data becomes really apparent if you reopen the same image many times for editing and re-save it, or if you try make a really large print from an image that has a high compression ratio.
How a JPEG Image is Different from a RAW Image
An in-camera JPEG image file is data from the camera's sensor that has been processed by the camera, and is nearly analogous to being a printed image. Like a photographic print, this image file is more limited in the capabilities for improvement.
On the other hand, a RAW image file is typically data straight from the camera's sensor, or possibly with minimal processing of that data, and is more like a photo negative which needs to be developed prior to making a print. Thus the RAW image file will be much larger.
Now, while RAW image files are much larger and take a bit more time to write out to the memory card, they provide nearly all of the information available to the camera from the digital sensor. Having all of this information in your image file gives many capabilities that aren't available from a JPEG image file.
What You Can Do with a RAW Image that You Cannot Do with a JPEG Image
For example, if the white-balance is not quite right in the image, for example if it has a red or blue cast to it, a RAW file provides the ability to change the filtering on the interpretation of the data to mask out the color cast from the ambient lighting.
While this can be done to some extent with a JPEG image, the flexibility in the RAW image gives much more power to fix the color casting in a picture. You can easily make a picture with a really red cast from incandescent light bulbs into one which looks quite natural.
Fixing More than Just White Balance
There is also much more flexibility in correcting exposure when developing the RAW image than after it is in JPEG format. You usually have a lattitude of up to three "stops" of exposure with RAW image files - this is a much greater lattitude than is available in a standard JPEG image.
For example, if the JPEG image has clipped highlights or shadows, that data is forever lost. However when processing a RAW image file it is usually possible to recover details in those highlights and shadows to add more depth to an image.
This can be very important for images with a large range between highlights and shadows, allowing the details in both to be provided in the final image.
RAW Advantages Outweigh the Disadvantages
Even though processing RAW image files takes additional storage capacity, as well as process steps and time in working with pictures, the overall benefits of the final output can often be well worth the effort.
The choice of whether to shoot pictures in RAW or JPEG is determined on how much effort post-shoot one wants to put into the pictures.
And while initial forays into processing RAW image files may be a little confusing and daunting, becoming comfortable with processing RAW image files can open up many new options, also save pictures which otherwise would have been lost.
