During the early days of photography, it was all film cameras. The image gets captured on the film, also known as the negative. The final process of transferring the negative to paper is known as processing. This processing happens in a Darkroom.
In this digital age, things have changed a lot, and the film got replaced by a combination of camera sensor and memory. The final image will be saved on a memory device like an SD card. Darkroom got replaced by post-processing software like Lightroom.
You may not be able to capture all the tonal details in the image due to the dynamic range limitations of your camera. So, you will have to do some basic image retouching while post-processing.
It helps to fix minor exposure corrections and white balance problems. Sometimes, you will have to crop your image to get the desired image composition. So, you need to depend on a post-processing tool.
If you are planning to send images for a photography competition, then it is a good idea to keep a copy of the RAW image from the camera. Read the rules and regulations of the competitions and do only the retouches which are allowed.
Post-Processing for the Web
Nowadays, it is essential that a photographer shows his presence online. So, he/she needs to have a portfolio site along with Instagram, Facebook, and other social media accounts.
You may be using a DSLR camera or a mirrorless camera which can capture image at 15 megapixels or above. So, you will have a big JPEG file or a RAW file at the end of the day. If you try to upload the JPEG image directly to your website, then it would occupy lots of space in server. The bigger file size will result in an increase in page load time, which will bring down the user experience.
If you do the same uploading procedure to upload images to Instagram or Facebook, then you can see a drastic drop in image quality. So, when you are uploading images to the web, you should optimize the image resolution to that of web quality for the best experience.
You may be using Adobe Lightroom for photo editing. For example, when you are exporting images for social media sites like Instagram, you need to crop the image in the correct aspect ratio. Finally, you need to use the right Lightroom export settings for Instagram for the best user experience. You can upload the same images to your portfolio site and Facebook.
Post-processing for Prints
If you are planning to take prints then capturing the image in RAW format would be the best option. You get all the details in your image. You can resize or change the image resolution according to the size of the print. Sometimes, you may have to go for image enlargement for a big size printing.
If you are using Lightroom, then ensure that you use the right Lightroom to Print export settings. Otherwise, it will result in a pixelated print, especially if you are printing big. It applies to all photo editing software.