Q-Eng

TED-Ed 024・・How to take a great picture（素敵な写真の撮り方）　　代表頁に戻る　　　　　　　　　　

03分・・190wpm　　　2013/09/29 新出


Hmmm, that's not what we want, is it? Today's digital cameras do a lot for us, but there's no replacement for the human eye. It's important to learn how cameras work with light to create an image, that way we'll know what's going on when it's time to capture a moment.

There are three variables that determine if you're getting the right amount of light for the correct exposure. With a manual camera, we're able to change any of the variable ourselves.
Different settings can result in really different pictures. Let's look at the process together.

First, see this here? This is the aperture（絞り）. It's the hole that light passes through. If we make the aperture big, we'll have more light, true, but the sharpness of your photo will decrease very quickly from your focus point, backward and forward. This is what we call shallow depth of field. If we have a very small aperture, we'll have less light but a deeper depth of field. For portraits, it can be nice to have a sharp figure separate from a somewhat blurry background so I would suggest a large aperture. Aperture is measured in f-stops. This can get a little confusing because lower numbers mean bigger apertures and higher numbers mean smaller apertures.

Next, there's shutter speed to think about. The shutter acts like a curtain that covers the sensor, and it only opens when you release the shutter button. If we want less light, we open the shutter for a shorter time. If we want more light, we open it for a longer time, but we run the risk of getting a motion-blurred picture. The speed is measured in seconds and fractions of seconds. For shooting sports or anything with a lot of movement, we'll need faster speeds. For taking awesome night landscapes, longer exposures will be better, but we'll need a tripod to steady the shot and prevent motion blur. Another cool thing we can do with light exposures is light painting, drawing in the dark with a torch or the light of a cell phone.

Lastly, ISO sensitivity controls how sensitive the sensor is to light. If we use low sensitivity, we'll need more light to register a photo. With a higher sensitivity, we'll be able to get a picture with less available light. 100 ISO is a low sensitivity, while 6400 ISO is a high one. If we increase sensitivity, we'll be able to use faster speeds and smaller apertures, but we'll get noisier images. Good thing we have something to tell us if we're getting the correct amount of light to get a good exposure, the light meter. Sound good to you?

Now it's time to get out there and practice taking pictures under different conditions, so you know what to do any time you want to take the best picture.