A RAW file is the digital equivalent of a negative or transparency in a film camera. It is the actual data that was captured by the sensor when the photo was taken, without any in-camera tweaking or tinkering. If you set your camera to shoot JPGs it will still capture the RAW data, then perform some pre-set processing, save the JPG file and then discard the remaining data. What we would like to do is to keep the RAW file so that we can make the processing decisions.
The letters R A & W are not an acronym and do not actually stand for anything. It just means that the file contains the unembellished data that the sensor recorded. A RAW file is not even an image file, it just contains the information that an image file can be constructed from. In order to create an image, we need to use a piece of software that runs on a computer that will allow us to manipulate the image data. Don't worry, this is not as complicated as it sounds. Some of the better known software packages include PhotoShop, Elements and Lightroom. The rest of this blog will be based on Lightroom as it is my particular tool of choice.
Lightroom is a non-destructive image editor. This means that instead of making changes directly to the RAW file, Lightroom creates a separate file called a Sidecar (or XMP) file that contains the edited information. In order to produce a final image, you Export the file which means that Lightroom will analyse the RAW file, apply any editing information in the sidecar file and use this information to produce the final image file. In fact, you can base several images on the same RAW file by creating separate sidecars: say, one for colour, one for B&W, one cropped for square or letterbox format, etc. The data in the original RAW file remains untouched. You could even mark the RAW file as read-only, as nothing should ever need to write to it (though, depending on your operating system and software configuration, your mileage may vary). If you are not happy with with a particular edit, just delete the sidecar file (Lightroom contains a Remove Image option which does just this).
Although RAW files can be quite large, the sidecar files are tiny, so there is no great overhead to storing them. For instance, a RAW file from my 12.3 megapixel Nikon D300 is 20Mb, the sidecar file after processing is 7Kb and the resulting exported JPG is 8.4Mb.
Using Lightroom, you should never need to directly interact with a sidecar file since Lightroom handles all of this transparently, but it is important to remember the significance of the sidecar as we will be discussing its impact in future blogs when we begin processing images.
Okay, after all that rambling, what should you take away from this? The important thing to consider if you want to be able to process images effectively, is to always shoot RAW (or even RAW+JPG if you're finding it hard to break the habit). In future blogs I will explain how to use Lightroom to manipulate your RAW files for maximum impact.
The content of this blog entry, as with all my blog entries, is my own personal opinion. I don't profess to be the fount of all knowledge on any particular subject; I'm just a guy with a camera and a computer, and around forty years experience taking photographs, both film and digital. I am still experimenting and learning, and I've done more things the wrong way than the right way, and from this I have learned what works and what doesn't. To quote Albert Einsten, "Anyone who has never made a mistake has never tried anything new." There may be a great many blogs, books or magazines that take a different view to my own and that's how it should be. There is never any single, definitive way of doing things, but what I write about here is what works for me. If it works for you too, then that's great!
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