For the record
In the days of argentic cameras, negatives were developed in a darkroom. Today the principle remains the same but the darkroom has become a computer and the whole process is done digitally.
On current digital cameras (cell phones and tablets too) and depending on their range, you can choose the file format between RAW and JPEG
To put it simply, JPEG is a compressed format with color and light parameters already set by the camera. The RAW format is the raw version with a lot more information, it's the closest to the photo negative we had on our film some time ago.
Thanks to this format we can work on the color, the light, the grain, the details...
That's why the raw photo is always a bit dull, desaturated and less dynamic than a photo in JPEG format because the photo is not yet developed.
Why develop your photos?
A photo taken in JPEG is already developed automatically so why take a raw photo to develop it ourselves?
We develop our photos to enhance an image and bring out information and / or an atmosphere more accurately.
When there are big differences of light, (a very contrasted image with a strong dynamic) the camera must make choices to compress the photo in JPEG.
For example if you have a backlight, the camera will either overexpose the part where there is the most light or block the dark areas of the image, so you have to take the photo in RAW format to catch up the information during development.
It is therefore very useful in landscape photos, portrait, evening photos ...
If you take pictures quickly to share them immediately with friends, JPEG will do the trick.
What do we use to develop a photo today?
The raw photos are developed with software that allows to work on the parameters of the photo.
The best known is "Lightroom" (which is often confused with Photoshop) but there are also "Capture One", "DXO PhotoLab" "ACDSee"
These softwares will be able to apply modifications to the photo in order to bring out the colors and the light that you want.
The development software are for the most part non-destructive, that is to say that they do not act on the original file. They make a copy and apply parameters on it as for a preview.
The image above is the raw RAW photo I just imported from my camera.
We can notice that the clouds are very white and that there is no more information in them. It is said that the sky is overexposed.
By decreasing the Highlight slider we can recover some information but the overexposed parts are not recoverable.
The RAW format allows some things but it is not magic. That's why the photo must be well exposed at the beginning.
On the photo above we have recovered information in the shadows by increasing the value of those.
This kind of manipulation is difficult on a file already compressed like the JPEG.
Here we have corrected the defects of the lens because all lenses create distortions and vignetting.
It is always good to correct them especially for landscape photos.
Here is the same picture but taken so that the sky is not overexposed. In this way I can recover a maximum of information in the sky.
Here, the sky is well exposed but the best is to make a mixture of several photos to have information in the sky and in the forest which is darker. This is called bracketing.
Here I hope that you will have liked these small explanations. You can still do a lot of things like transform the colors of a photo or the brightness of each color. If you have any further explanations on the art of development, please feel free to write them in the comments below. I'd be happy to read you.
See you soon Nicolas