Hmmm, that's not what we want, is it?
嗯...这不是我们想要的照片吧？
Today's digital cameras do a lot for us, but there's no replacement for the human eye.
现在的数码相机有很多功能，但还是无法取代人眼。
It's important to learn how cameras work with light to create an image,
我们必须知道相机是如何用光形成影像，
that way we'll know what's going on when it's time to capture a moment.
这样你才会了解当你按下快门时，到底发生了什么事。
There are three variables that determine if you're getting the right amount of light for the correct exposure.
有三个变量决定了你能否得到适量的光，来产生正确的曝光。
With a manual camera, we're able to change any of the variable ourselves.
对于一台手动相机来说，我们能够调整任何的项目。
Different settings can result in really different pictures.
不同的设定会产生不一样的照片。
Let's look at the process together. First, see this here?
我们一起来看一下过程：首先，看到这里了吗？
This is the aperture. It's the hole that light passes through.
这是光圈，它是让光穿过的小洞。
If we make the aperture big, we'll have more light, true,
如果我们把光圈放大，就会有更多的光通过，
but the sharpness of your photo will decrease very quickly from your focus point, backward and forward.
但是如果你拍照的距离超出你的焦点前、后一小段范围，照片的清晰度就会快速地下降。
This is what we call shallow depth of field.
这就是我们所称的浅景深。
If we have a very small aperture, we'll have less light but a deeper depth of field.
如果光圈非常小，通过的光会变少，但会加大景深。
For portraits, it can be nice to have a sharp figure
对于拍摄人像来说，应该要有清楚的身体轮廓，
separate from a somewhat blurry background so I would suggest a large aperture.
并且与稍微模糊的背景有所区别，所以我会建议使用大光圈。
Aperture is measured in f-stops.
光圈的单位是光圈值。

This can get a little confusing because lower numbers mean bigger apertures and higher numbers mean smaller apertures.
这里很容易让人混淆，因为较小的数字，代表较大的光圈；而较大的数字，则代表较小的光圈。
Next, there's shutter speed to think about.
接下来，我们来看快门速度。
The shutter acts like a curtain that covers the sensor, and it only opens when you release the shutter button.
快门的作用就像窗帘，它遮盖着影像传感器。当你放开快门按钮时，快门才会打开。
If we want less light, we open the shutter for a shorter time.
如果我们想要比较少量的光，快门打开的时间就要很短。
If we want more light, we open it for a longer time, but we run the risk of getting a motion-blurred picture.
如果我们需要较大量的光，快门打开的时间就要加长，但会这么作会有风险，就是拍出一张模糊的照片。
The speed is measured in seconds and fractions of seconds.
快门的速度单位是秒，甚至只有几分之一秒。
For shooting sports or anything with a lot of movement, we'll need faster speeds.
要拍摄运动或是大量动作的画面时，我们需要较快的快门速度。
For taking awesome night landscapes, longer exposures will be better,
但是如果要拍摄很棒的夜景，就需要更长时间的曝光，
but we'll need a tripod to steady the shot and prevent motion blur.
这时我们需要一个三脚架来固定相机，以避免晃动造成模糊。
Another cool thing we can do with light exposures is light painting,
另外一种很酷的曝光方式，称为光影涂鸦，
drawing in the dark with a torch or the light of a cell phone.
就是在黑暗中用火把或是手机的灯光来绘图。
Lastly, ISO sensitivity controls how sensitive the sensor is to light.
最后，ISO控制着影像传感器对光线的敏感度。
If we use low sensitivity, we'll need more light to register a photo.
如果我们调低光线敏感度，我们就需要更多的光线才能拍照。
With a higher sensitivity, we'll be able to get a picture with less available light.
使用较高的光线敏感度，我们就可以用较少的光线来拍出照片。
100 ISO is a low sensitivity, while 6400 ISO is a high one.
ISO值100是指光线敏感度较低，而ISO值6400是很高的光线敏感度。
If we increase sensitivity, we'll be able to use faster speeds and smaller apertures, but we'll get noisier images.
如果我们提高光线敏感度，我们就可以用更快的快门速度和较小的光圈来拍照，但是影像会有较多的杂点。
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.
有个好消息要告诉大家：如果你想要得到适量的光来产生正确的曝光，你可以使用测光表。
Sound good to you? Now it's time to get out there and practice taking pictures under different conditions,
听起来不错吧？现在，你应该出去走走，在不同情况下去练习拍照，
so you know what to do any time you want to take the best picture.
这样你就会知道如何拍出最棒的照片了。