Your aperture is one of the three most important settings on your camera. It’s a lot like adjusting the lights in a room to set the mood. Photographers adjust their aperture to achieve a nice Bokeh.
Bokeh is the blur, or the aesthetic quality of the blur, in out-of-focus areas of an image.
If you own a “fast” lens (that means a lens with a low f-number) then you’ve probably experienced the creative effects of bokeh. If not, set your aperture to the highest aperture (low f-number) and focus on something until the background looks like a blurry mess. If your new to photography then check out our advice on how to achieve blurred backgrounds.
Being able to create a nice bokeh is wonderful, it’s important to know when and how to use it. The photo above was taken before a Christmas party, but I didn’t need to tell you that because you see all the tables in the background and their place settings. Sure, I could have opened my aperture all the way to f1.8 (I used the Nikon 50mm f1.8D lens) but then the entire background would have been blurred and you would not really know where or when the photograph was taken. Sometimes it’s better to choose a middle ground (I used f4.5 in the image above) and slightly blur your background (you may have to raise your ISO to get the proper exposure, the image above was shot with an ISO of 2000) so that you retain some of the context of the photograph.
In the end you’ll have to choose between isolating your subject and cutting out any background distractions or leaving a little background there to tell the rest of the story. Had the room been full of a bunch of people I would have used a higher aperture (low f-number) and blurred them
right off the planet out of the picture.