if i'm not wrong, use a bigger hood would allow you to have that effect in your photos. Identically, you can also create that effect in Photoshop.
The effect you're talking about should be Vignetting.
Advise for newbie is to do it in post process, through software, where it is more controllable..
Sometimes this vignetting effect is not desirable for every kind of shoot
and once it is achieve in your original raw shot (not through s/w), it takes quite a lot of effort to remedy it later part in your PP flow if you fell that vignetting may not suit final picture in the end..
Normally happens in ultra wide angle, where if you plonk in a thick filter or stack filters (put more than 2), the corners (which is the widest angle you are taking) will be clipped off by the filters. It's normally quite a hard clipoff, so if you see a soft nicer looking vignetting, most likely it's software processed.