Imagine you've just returned from a day out and about, with your camera swung around your neck. An SD card full of special images, or so you hope. Upon opening up your favorite photo editor you discover that one very special image is smiling back at you. Upon closer scrutiny you find that the image isn't so ... perfect, after all. Your composition is spot on, but a few shadows are a bit darker than you prefer, and more saturation would be great. Or worse yet, you realize the camera picked the wrong white balance - the entire image is a bit colder, or blue toned, than you prefer. You can try to fix those issues, but a JPG image just doesn't have enough data to get the job done.
That is why I shoot everything in RAW, no matter what I plan to do with the image. A RAW image file records 10 times (or so) the data that a JPG image records. That might not mean a lot to you, but let me show you what the difference is. This morning I took an image that will be the perfect example of why more data is such a good thing. I will show you that image four different times, each representing a extent of processing. Ok, that didn't make much sense to me either, so let me show you.
This first image is straight out of the camera. No editing at all. Overall, not a particularly bad image, but I think it's missing that pop. Let's see what we can do to help it out a bit.
This next image is what can be done with a typical JPG file. You'll notice some change, but nothing that gives us the "wow" factor. Because I originally used a RAW file, I had to stop my editing short - trying to mimic the extent that a photo editor could improve a JPG image. Amongst other changes, I lightened it up a bit, and to be honest I'm not even sure it looks any better.
This image is edited as much as I would normally edit any RAW image, with the exception of running it through an HDR (high dynamic range) process. You can tell that I improved most aspects of the image ... I even warmed the image a bit by changing the white balance. You can't do that with a JPG file.
And finally, I ran the above file through the HDR process and came up with the image below. Which ever preference you have (HDR or not), a RAW image gives you the flexibility to go either way. Generally speaking, if I have a lot of shadows that I want to bring out, or I want to better balance the highs and lows of the dynamic range, I will run it through HDR.
And that is why I always shoot in RAW. Of course, not every camera allows for RAW files - most don't. But, if you have the option, I hope this helps to swing you in that direction. If nothing else, most D-SLR cameras allow you to shoot each image in JPG and RAW at the same time. That way, you can use the JPG files as you normally would, and you have the RAW image just in case you get that very special picture smiling back at you.
Until we meet again ... enjoy !