Should I Shoot RAW or JPEG Files?

That's a good question, and it's one without an easy answer.  You can find very good photographers that have strong beliefs on either side of the issue.  But we should begin by answering a more basic question--what the heck is a RAW file anyway?

Somewhere in the menu system of your dSLR, you'll find an option to shoot RAW files instead of JPEG files (or to shoot both).  Technically speaking, RAW files are not image files--they are simply files that contain the data recorded by your camera's sensor when you took your picture.  Because of this, you can't just open the file in any application like you can a JPEG file (which is a true image file).  The file must be interpreted by software to generate an image from the file.  And RAW formats are specific for each camera model, so you have to have software that has been updated after your camera was released or you may not be able to edit your files.  Without any work done to them, RAW files often look less sharp than JPEGs, and the colors seem "flatter" than they should (less contrast).  They are also larger, so they take up more space on your memory card and hard drive.  You can't print a RAW file either.  If you want to print it, you're going to have to save your file in a different format (JPEG, TIFF, etc.).  Have I sold you on using RAW files yet?

But wait, there's more.  If you are shooting JPEG, your camera is saving actual image files and applying settings like white balance, sharpness, etc. directly to the file, and it will compress the file to take up less space on your card.  And don't let any one fool you.  JPEG compression is pretty good (if you use the best settings available on your camera).  If you take a photograph in JPEG with just the right exposure (with detail in all the highlights and shadows), you'll be hard pressed to find any significant deficiency in image quality when compared to a RAW file of the same photograph.  I've enlarged 6 megapixel jpeg images to 4ft by 6ft, and they were fine.  Because of this, some photographers argue that there's no real reason to even bother with shooting RAW.  All you do is waste space on your memory card (so you can't take as many pictures), waste space on your hard drive (so you can't store as many pictures), and waste time editing them on your computer, instead of taking pictures.

So why shoot RAW?  I still think there are good reasons to do so, and I shoot RAW files almost exclusively for the following reasons:
  1. RAW files are 2-3 times larger because they contain more data.  They contain all the data recorded by the sensor as well as the settings you used to record your image (white balance, etc.).  When your camera compresses raw data into a JPEG file, it's throwing out information that you could use as you're editing your photograph.  There's nothing wrong with compressing an image, but I'd prefer to do that after I'm done editing it.  I want to do my editing with all the information my camera is able to capture.  This is especially important for me, since I have red-green colorblindness.  I don't see color problems as well as others do, so I want all the data I can possibly have to make corrections later.
  2. Everyone makes mistakes.  RAW make more data available to you that you can use to correct mistakes.  Suppose the lighting outside changed from sunny to shady, but you forgot to adjust your white balance.  If you shot in RAW, you simply apply a different white balance setting to the file in your software, and it's like you never made a mistake.  Suppose you were shooting a back-lit bird with dark feathers and applied exposure compensation to make sure you get details in the feathers.  Then you see on the other side of you a Great Egret (big white bird) catching a fish.  You turn around quickly to get the photograph, but do not have time to fix your exposure compensation.  You take a picture, and the egret then flies away.  If you were shooting RAW, there's a greater likelihood that you'll be able to recover detail in the egrets white feathers.
  3. High Contrast Scenes.  When shooting in harsh lighting, RAW files give you more to work with, especially in the highlights.  Consider a sunny day late in morning.  Shooting with the sun in front of you is difficult lighting regardless of the format you're using.  There's only so much you can do.  But one thing you can do that helps is shoot in RAW.  I always try to expose for the highlights and use software to bring detail out of the shadows.  But you can sometimes get a fair amount out of the highlights as well.
  4. Software.  It used to be that people joked that RAW stood for Really Awful Workflow--it just added extra time to photo editing.  But today, if you are using good software (Lightroom, Aperture, etc.), this simply isn't true any more.  The files are larger so they take longer to load onto your computer, but aside from that, the workflow is identical.  I spend no more time editing RAW files now than I spent editing JPEG files before I made the switch.  I do most of my work in Lightroom.  This software also lets me export images from Lightroom as JPEG files to my hard drive, my smugmug site, or facebook.  So I can easily send a JPEG file to a print service while keeping my RAW file in Lightroom.
  5. Memory is Cheap.  Memory cards just keep getting cheaper.  I carry about 26 gb of memory cards with me when I shoot.  I'm good for more than 1500 photographs in the field.  You can get a 1tb hard drive now for about $100.  If you do a good job of deleting photographs you'll never use, that hard drive will store years of good pictures.
  6. DNG.  Once I do my get all my photos into Lightroom and delete the ones I don't want, I convert my files to DNG format (adobe's RAW format).  This way I don't have to worry about one day using software that doesn't support the RAW format used by my current camera, and the images are smaller than Canon's RAW format, so I save space.
I shot the above picture of a Loggerhead Shrike in terrible lighting.  I shot this image at about 10:40am with the sun in front of me and to my left.  It was causing all sorts of problems to my exposure, especially in the highlights on the top of the birds head.  But in Lightroom, I was able to get a lot out of those highlights to give me a usable image that would otherwise have been unusable.

Don't feel compelled to shoot RAW files.  JPEG can give you images that are plenty good. But if you have (or can afford) the memory, storage and software to shoot in RAW, I suspect you'll be able to get more out of the images you take.