Why it might be a good idea to save
RAW format files from your camera.
This is not intended to be a tutorial on RAW photo file processing or a detailed accurate scientific explanation of the the way RAW and JPEG files are produced it is just simply a quick high level overview that may give a flavour of what RAW files are and why it may be a good idea to save them on your camera. Even if you don't know what to do with them now they may turn out to be very useful later if you decide RAW processing is for you. If you can't be bothered to read anymore then just jump to the bottom of the page to see some before and after shots to see the sort of difference it can make.
When I went on my sailing trip in the yacht Callisto I took with me my first proper digital mirrorless camera, a Panasonic Lumix G6. I didn't know how to use it properly and didn't have an instruction manual with me on the yacht so it was just left to sort itself out in "Intelligent Auto Mode". However, I had heard RAW processing mentioned before I went and luckily I had changed the options in my camera to store BOTH RAW and JPEG format files for every photo before I went. That turned out to be a great move because a couple of years after the trip when I discovered the joys of RAW processing I was able to go back to the RAW files I had stored from that once in a lifetime trip and salvage many of the photos!
As the name implies digital cameras don't use film to produce a photo they just produce a file of data from the output of a sophisticated light sensor. Instead of processing a film to get the finished photo they process the data file using complicated algorithms to make sense of the jumble of digital signals and magically produce a photo file, the ubiquitous JPEG format file that most people are familiar with, those files ending in .jpg or .jpeg that you download from your camera.
However, the JPEG file is a compromise based on what the camera (actually a small computer) thinks the photo should look like calculated using the exposure settings of the camera at the time. The JPEG file, to save space, is a "lossy" compressed file so basically once the camera has decided what the JPEG should contain it effectively throws away any extraneous data so it is gone for good. You may be able to enhance the JPEG photo to an extent later, by using Photoshop or similar, but you will only be able to enhance what remains, you won't have all of the data the camera originally captured.
However some advanced compact cameras and almost all DSLR and Mirrorless system cameras have the ability to save RAW format files as well as, or instead of, JPEG files. The sensors in most modern digital cameras are small miracles of engineering and have a very wide exposure range (what is known as dynamic range and for most modern cameras this is somewhere between 11 and 15 EV). This means that they can record a very wide range of light levels from details hidden in shadows to details hidden in very bright highlights. The RAW files contain all of this information (so are larger than JPEG files) and it is effectively these RAW files that the camera uses to produce a JPEG file in the first place before throwing the RAW data away. However, if we save these RAW files then process them ourselves, with some special RAW file processing software, we can decide exactly how our final photo appears and what details we want to display. Moreover, instead of just taking an average value over the whole photo, for instance lightening the whole picture, we can choose for example to selectively boost (lighten/reveal) the details in the shadow and at the same time darken the highlights to reveal details in them as well. This can be especially useful when processing photos of sunsets where it can be tricky to get the exposure right in camera and even if you do you will often end up with either a burnt out sun or a dark silhouette landscape. The software also enables us to control the level of digital sharpening in the photos, colour tones and saturation, level of digital noise reduction applied (a topic of it's own!), etc. "Post Processing" of your photos then becomes an art form in it's own right. Most professional photographers will "Post Process" their photographs as part of their standard workflow to get the best out of them.
There are many software applications available for RAW and Post Processing digital photo files ranging from free Open Source software (e.g. Rawtherapee and Darktable) to eye wateringly expensive software packages. You may also find that some cameras come with a free application that can process RAW files, although possibly in a more limited way. At the lower end of the price range of paid for software packages I have found Affinity Photo is remarkably powerful but at a very reasonable price. You can also effectively buy a RAW software processing software service on-line (Something like Adobe Lightroom used by many Pro photographers) for a monthly fee so you can try out software just for a month for the price of a round of drinks.
Personally as I use a camera with a small Micro Four Thirds (M43) sensor (which is more prone to displaying digital noise at higher ISO levels) I currently use the DXO Photolab 3 Elite software package most of the time as the "DXO PRIME" Denoising technology built into it is extremely good at removing digital noise (the fuzzy blurriness you can sometimes see in photographs especially when taken in dim/dark conditions) while at the same time preserving detail. Beware though that, at the time of writing, DXO Photolab does NOT support Fujifilm cameras using the X-Trans sensor as this is different from the Bayer sensor used by most other cameras and needs different algorithms to decode the data which, thus far, DXO have resisted including in their software and have said they have no plans to do so.
Below are a few examples of the difference it can make processing a RAW file when compared to the original straight out of camera JPEG file just to whet your appetite and maybe give you the incentive to find out more (masses of information and youtube video tutorials available on the internet) and have a go yourself. The results don't have to be as obvious as the examples below, it can just be the subtle raising of a few shadows or lowering of a few highlights that can make all the difference to a photo or not changing anything other than de-noising an image. For me, buying a good RAW processing software package was like giving myself an upgraded camera, the results were that good!
Below is the JPEG file the camera produced for an accidentally under exposed photograph
And this is the exact same photograph manually processed from the RAW file showing just how much data the Sensor had really captured and what could be recovered. Wouldn't you have been relieved if that had been a wrongly exposed wedding photo!
The example below shows a photo taken from a yacht entering Dartmouth Harbour. The automatic exposure system of the camera had metered for all of the light being reflected off the sea and the large patch of sky in the photo rendering some of the shoreline detail dark and indistinct. I had no time to set the camera up for the preferred exposure as I was busy navigating into a harbour (and at that time didn't know how to operate the camera anyway!). This has produced a fairly flat and bland looking view.
The photo below has been processed from the RAW file of the exact same photo as above to bring out more of the detail that the camera had actually captured. Raising the brightness of the shadow areas and reducing the brightness of some of the highlights. Also sharpened a little and fine contrast and colour saturation increased bringing out the details of the clouds to give a photograph with more "pop". This isn't "photoshopped", all that detail was in there it just needed to be let out and the photo presented more like our eyes were able to see it!
Finally just getting a bit artistic. This was a photo of an old barn taken on a foggy December day. In this case there is nothing actually wrong with the original JPEG file, the camera interpreted it basically just as the scene really looked.
But now below I have deliberately manually over processed it using the RAW file to produce a more dramatic looking picture.
Slightly cropped, heavily sharpened and different colour channels selectively saturated or desaturated to give a more stark gritty look.