An item that new students that are also new to photography get confused on is how to get the sharpest images. Often times new students believe that getting the widest aperture lens possible if they can afford it will give them the sharpest images, this is NOT true.
If you ask any of your professors or any other professional photographer, they will tell you that your sharpest images happen around 2 stops below your widest aperture. As an example, I have the Canon EF 50mm F/1.4 USM lens, but I never shoot this lens at F/1.4 as it performs much better sharpness-wise at around F/2.8 on a full frame camera or F/2 on a 1.6x crop body. This first image was shot using a EOS 5D Classic with EF 50mm F/1.4 @ F/1.4
When you shoot with this lens wide open you get very strong halation aka dreamy look with some Chromatic Aberration in your images as well. After the dreamy look diminishes at F/2-F/2.8 you get very strong colors and contrast, which in turn will make your images really “pop”. When using a really wide lens, you don’t want your aperture smaller than F/8 because then diffraction starts to soften them again.
This sharpness is how things apply to prime lenses, which have extremely wide apertures. When dealing with zoom lens, it works a little different, on a zoom lens, the optimum sharpness range might be smaller but they are generally sharpest at their widest apertures of F/3.5-F/5.6 or even F/6.3. Now with a zoom lens as I mentioned the sharpness range is usually smaller but you can generally count on sharp images from the starting aperture to around F/8 or maybe F/10, anything past that and again you get diffraction again. On this second shot on my EOS 5D Classic with EF 50mm F/1.4 @ F/2.8 notice even the bokeh is better.
Now that you are more informed about using aperture to get sharp images, get out there and make some great ones!