Most of the time I have problem with the lightning of my images even after post processing with Adobe Photoshop. I searched the net and I found that people use the RAW format instead of jpg. Do I need to use RAW format If what I only need is lighter and sharper images for my blog, or will using RAW format will add more overhead of post processing?
Always shoot RAW if you can. A RAW file is a capture of all the light that hit the sensor photocells at the time of exposure. This allows you to read, interpret and convert that data in any number of ways. A JPEG is just 1 out of 1000+ ways you can interpret that RAW data. Depending on your scene, camera and the sensor, a RAW file will give you anywhere from 3-7 stops of exposure compensation. Think of it as realizing your shot was under exposed (not enough light) and now you can go back in time and essentially re-take that shot at the right exposure from the comfort of your laptop/computer. This is referred to as Dynamic Range. Assuming you are using a DSLR or mirrorless, you may as well use a point and shoot if all you do is shoot JPEG. The benefits of RAW files and interchangeable lenses are the two main reasons to use a DSLR or mirrorless camera.
I'd look at this one somewhat differently; you say that you want "lighter and sharper" images, which are actually two different problems.
- To get lighter images, you need to either get more light into the camera, or change what the camera does with the light. To do the first, you can either have a longer exposure or a wider aperture; to do the second, you can increase the ISO you're shooting at. Assuming you're not in full manual mode, you can add some exposure compensation; if you are in full manual mode, then just tweak one of the parameters.
- To get sharper images, you need to work out why your images aren't sharp in the first place. There are a whole load of potential reasons for a lack of sharpness, but without seeing an image, it's going to be tricky to work out which of them apply to your situation.
How does RAW vs JPEG apply to all this? What RAW gives you in this situation is more latitude for rescuing things if you didn't get your settings right in camera - for example, if you want to add a stop of brightness to an image, you'll get a better result if you do it from a RAW file than if you do it from a JPEG. However, you'll get an even better result if you get your settings right when taking the photo in the first place, so that's what I'd concentrate on, rather than worrying about your post-process workflow.