Raw versus JPEG formats

Jpeg is a compressed file format used for displaying and printing images. Jpeg is also called a lossy format, because repeatedly saving a jpeg file will slowly degrade the quality. RAW format contains all of the camera data captured by your camera's sensor.

            Most photographers start out shooting in JPEG, because the files are smaller and you don't need a RAW editor to save them. However, RAW files store much more information, especially in the shadows and highlight areas, and allow for custom white balancing to be done. When shooting raw, white balance, shadows/highlights, tone (contrast), sharpening, color space, and exposure (to a limited extent) can be managed in your computer. An extra stop of exposure in the highlights and shadows can be recovered when shooting in raw. Many serious photographers shoot in RAW, although some excellent macro photographers mainly shoot in JPEG because they may not have time for raw file processing.

Let's review some differences between RAW and JPEG files formats:

RAW files

Pros

• Saves all of the data from your camera sensor
• Gives you more data to work with when adjusting color space, white balance, tone, exposure
• Has12-14 bits of color vs 8 bits in jpeg
• Has a higher dynamic range

Cons

• Needs to be converted to TIFF or JPEG to be displayed/printed
• Larger file format
• A RAW editor usually needs to be purchases, and upgraded for newer camera models
• Sometimes needs contrast adjustment

JPEG files

Pros

• Smaller format allows more photos to be stored on a memory card
• Photos can be instantly printed or displayed on the screen / web
• Some recent dSLR's, such as the D300, do an excellent job of noise reduction, sharpening, exposure control, etc. when creating a jpeg, saving the user time in post-processing

Cons

• - difficult to adjust exposure, recover highlights, and change white balance
• - lossy format means repeated saves slowly degrades image quality. Repeated changes can introduce types on noise known as JPEG artifacts

TIFF is another format. Data is stored in 8-bits, but the is no loss with repeated saves, and no compression. TIFF files can be very large, and people sometimes only store TIFF files if they have done extensive processing in photoshop and want to save a lossy format.

I usually shoot in RAW + jpeg format. At first I only used jpeg files. Then I started processing raw files more often, which took up a lot of time. Now I find myself being able to get great color and exposure in my jpeg files, especially when shooting macro, and using them is saving me time. It is possible to get it "right" in camera.

Here's an interesting viewpoint that goes against the grain of most people's advice, in the end you need to decide what is right for you

http://www.kenrockwell.com/tech/raw.htm

The big question - should I shoot RAW or JPEG?

It's really a personal choice. Someone shooting with a G10 recently asked me this question. I suggest you try shooting one dive in JPEG, one dive in RAW. See if you feel that the additional raw workflow is worth it to you. Try RAW first with some ambient light shots, that's where you will initially see the biggest difference in recovering contrast and some color, depending on depth.

Keep in mind that all photos saved in RAW must be convertered to JPEG (or Tiff) eventually to display them on the web or to print them. Your photo editing tools can't re-write a RAW file, only your camera can do that. Some RAW editors will maintain a list of edits in a separate file however.

Further Reading

Camera Settings for underwater photography

Camera sensor size, pixels, bit depth and dynamic range