Aperture

Aperture is described by photographers in the form of f/x.x

If your lens has numbers on it like 1:4.5-5.6 then that means it has maximum aperture of 4.5 at it's widest focal length and a maximum aperture of 5.6 at it longest focal length.

Aperture is the size of the opening of the inside of the lens that allows light through to the sensor in your camera. The lower the number, the larger the opening. The higher the number, the smaller the opening.

Aperture controls the depth of field that you have in your photos. The lower the aperture (say f/1.8) the less depth of field your photo will have. If you put three items on a table all staggered in distance, then set your lens on it’s maximum aperture (lowest number it can do) and take a photo (as close to the subject as your lens will allow), you will see that only the item you focused on is in sharp focus and everything else will blur out.

The more stopped down your aperture is (think f/16) the more depth of field your photo will have. Try taking the same photo as before with your aperture closed down (The highest number your lens can do). You will find that more of your image is in focus.

You will notice that when you are changing your aperture you will also have to adjust your shutter speed. Opening up the aperture will mean you'll have to speed up your shutter speed just as stopping the aperture down will mean you'll have to slow the shutter speed. Sometimes when we stop down too much (move the aperture number higher) we find that our overall image quality drops. This is because of physics and nothing can fix this phenomenon .

I would recommend experimenting with your camera and looking at your images at 100% and you will be able to see the point where it starts to soften your images. That is where you’ll find your limit for that lens and camera combination.

It may be different depending on the different lenses you are using but I would strongly recommend you do this as it will help you pick the best settings for image quality from the gear that you have.