Shooting In Manual Mode: Aperture
Note: This is part 4 of a 5-part tutorial series for beginners. Articles are as follows:
- Part I: Shooting In Manual Mode: Intro
Part II: Shooting In Manual Mode: ISO
Part III: Shooting In Manual Mode: Shutter Speed / Exposure Time
Part IV: Shooting In Manual Mode: Aperture
Part V: Shooting In Manual Mode: Conclusion (Exposure Triangle)
Aperture is the hardest concept for new photographers to understand, and for that reason I will skip the technical explanation (I’m not going to pretend I understand every bit of that explanation, heh). Just like every other setting on a camera, changing the aperture affects the brightness of your image (all other settings being equal). Aperture is measured in f-numbers.
Basically, the lower the f-number, the brighter the image. A lower f-number means there is a larger opening to let light in through your lens. Typically speaking, if your lens can go to a lower f-number than someone else’s lens, then your lens is more expensive. This is why your lens’ lowest f-number is listed right in the name of the lens–it’s that important. I have a lens that can go down to f/1.2, and it can practically take pictures in the dark (without a flash). A kit lens can normally go down to f/3.5 (or f/4.5 if it’s a zoom lens). The number that most people can rattle off is f/2.8; this is an industry standard of sorts for portrait photography.
As with everything else in photography, Aperture is not only about the lightness/darkness (exposure) of your image. Depth of field can be altered by changing your selected f-number. The best way to explain depth of field is with a photograph. This photo of some kind of vegetable cocktail illustrates the concept very well. The left image has a low f-number and only the front cocktail glass is in focus. The image on the right has a very high f-number and nearly every cocktail glass is perfectly in focus. The image on the left has a narrow depth of field and the image on the right has a wide depth of field. It should also be noted that the f/20 shot requires much more time and preparation to capture. Any photograph that uses a high f-number uses a very long exposure time and consequently requires a tripod.
Changing the aperture inevitably changes the look and emotion of your photograph (that is not necessarily true when changing the exposure time or ISO). When taking a portrait, a lower aperture is normally used so that the background is out of focus. If the background is in focus, it is competing for your attention. That is not desired for portrait photography. If you want to capture a landscape image, on the other hand, one typically wants everything to be in focus if possible; this requires a higher f-number. A higher f-number has a larger depth of field, but it requires a much longer exposure time. It is letting a much smaller amount of light into the camera, so a longer exposure is needed to compensate for this loss of light.