Can I control the focal length?

我能控制焦距吗？

Set the focal length on your lens.

给你的镜头设置焦距。

Empty eyes, can not find the focal length.

空洞的眼眸，找不到焦距所在。

The iPhone camera has a fixed focal length.

iPhone的摄像头有焦距固定。

That cone Angle is directly controlled by the focal length.

圆锥角度直接受到焦距的控制。

Camera lenses have two general attributes: f-stop and focal length.

照相机镜头有两项一般属性：f制光圈和焦距。

For me, one of the initial questions is how to set the focal length.

对于我来说，一个首要问题就是怎样设置焦距。

Two lenses of focal length 10 cm have a combined focal length of 5 cm.

两个焦距都是10厘米的透镜形成的组合透镜焦距为5厘米。

This is the ratio of the focal length of the telescope to its aperture.

这是指望远镜的焦距与其孔径的比值。

The focal length of the camera lens plays an important role in photo criteria.

摄影机镜头的焦距在摄影规范中起着重要的作用。

The focal length of the camera lens plays an important role in photo criteria .

摄影机镜头的焦距在摄影规范中起着重要的作用。

But once you have the focal length determined, everything else is a piece of cake.

但是，一旦你确定了焦距，其他事情就不值一提了。

Keep in mind that changing focal length will require refocusing in most zoom lenses.

要注意的是，对于大多数变焦镜头来说，焦距改变了，就得重新对焦。

Smaller sensors 'crop' the scene and make a lens appear to have a longer focal length.

更小感光元件会使得镜头产生更长焦距的效果。

Zoom lens a lens whose focal length can be varied continuously over a substantial range.

变焦镜头可以把焦矩在相当大的范围内连续改变的镜头。

The diameter of a sphere is four times the focal length of a concave mirror cut from it.

凹面镜如果是从圆球上切下来的，圆球的直径会是凹面镜焦距的四倍。

For the first shot he used a shorter focal length and the second shot he used a longer one.

先前的一张焦距短，第二张他用了长焦。

Depending on the lens' focal length, the image will deform and affect how the image looks in photos.

根据镜头焦距的不同，图像会随之变形并且会影响最终的照片效果。

The focal length you need depends on your distance from the burst and what you're trying to capture.

你所需要的焦距取决于你和被拍摄焰火间的距离，以及你想捕捉到怎样的画面。

You also lose the focal length 'boost' offered by smaller sensor cameras when shooting with telephotos.

同时在摄远时长焦镜头给更小画幅相机带来的冲击力也会随之消失。

The lens distortion model describes how the distortion coefficients change according to camera focal length.

镜头畸变模式描述了如何根据相机畸变系数改变焦距。

For example, the focal length of an 8" (203.2mm) aperture with a focal ratio of f/10 would be 203.2 x 10 = 2032mm.

比如，孔径为8英寸(203.2mm)，焦比为f/10的透镜，其焦距为203.2 x 10 = 2032mm。

Or, you can calculate the exit pupil by dividing the focal length of the eyepiece (in mm) by the focal ratio of the telescope.

或者，你还可以将目镜的焦距除以望远镜的焦比来得到出瞳尺寸。

For example, a telescope with a focal length of 2000mm has twice the power and half the field of view of a 1000mm telescope.

比如，与焦距为1000mm的望远镜相比，2000mm焦距望远镜的放大率和视场范围分别是前者的2倍和1/2。

The reason for this is that as we know, longer focal length lenses magnify the image, but they also magnify the camera shake.

正如我们前面所学，更长的镜头焦距虽然放大了图像，但同样增加了镜头抖动。

A good rule of thumb to minimise camera shake is to set the shutter speed at a minimum of one second divided by your focal length.

测算你相机的安全快门速度有一个好的方法，你相机镜头焦距的倒数，就是你避免镜头抖动的快门最小值。

Digital SLRs with a lens focal length of 300 to 400mm are recommended, but you can get away with a decent compact with a 10x zoom.

推荐使用带有300 - 400毫米镜头的数码单反相机，但如果有一架有10倍变焦镜头，性能良好的小型相机也可以。

Using a longer focal length and photographing stars far from the north star increase the distance stars will move across the image.

使用长焦镜头拍摄远离北极星的星星，会增加星星在相片上移动轨迹。

If you know the focal ratio but not the focal length, you can calculate it: focal length is the aperture (in mm) times the focal ratio.

如果你不知道焦距，只知道焦比(focal ratio)，你可以通过这样计算的得到焦距：孔径(单位是mm)乘以焦比就是焦距。