What excites ophthalmologists most, and what every lens-making company wants to achieve, is an “accommodating” lens that can change its focal length in the same way that a natural lens does.
最让眼科学家兴奋的，而且每一家人工晶体制造公司都想获得的，是一种“善于适应新环境的”晶体，能像天然的晶体一样改变它的焦距。
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。
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。
This can be a tedious process because the first time you create the plane, you have to rotate the camera and change the focal length at the same time to get a good match.
这个过程可能很乏味，因为你要先建立平面，还不得不去旋转摄像机，并调节焦距以得到好的匹配效果。
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203.2x 10 = 2032mm。
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。
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。
If you like taking photos of birds or other wildlife, or if you’re just a peeping Tom, you can get a superzoom camera with a built-in lens with an insane focal length.
如果你喜欢拍摄翱翔天际的飞禽和横闯森林的走兽，或者你想要偷拍对面的心动男孩，你可以选择具有内置镜头和大焦距的相机。
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。
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。
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 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。
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。
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。
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。
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。
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(focalratio)，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。
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 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 iPhone camera has a fixed focal length.
iPhone的摄像头有焦距固定。
How deep I should distort the building shapes by using wide angle focal length or if I should avoid it and use more close to standard values or even a telelens.
我通过使用宽角焦距应该使建筑形状弯曲到何种程度，或者如果我想避免它，使用更接近标准值乃至长焦镜头该怎么做。
Using a group of mirrors and a housing that's almost big enough to use as a coffin, Canon was able to stretch the focal-length on this SLR-specific lens to 5,150mm.
佳能的这款单反相机专用折反镜头采用了一组折反镜片，以及一个跟棺材差不多大的镜身，其焦距被拓展到5150mm。
They will basically be the same sensor and focal length, but one will be tasked to carry full color info, the other will capture only black and white but will be better at low light situations.
他们基本上将相同的传感器和焦距，但一个人的任务是将进行全彩色信息，另将捕获只有黑与白，但会在低光情况下更好。
The first shot was taken with a short focal length (around 70mm) and from a relatively close distance and the background looked quite far away and small.
第一张焦距约70 mm，在相对近的距离拍摄，背景看起来很远而且很小。
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。
If you know the FOV, sensor size, and working distance, you can compute the focal length of the lens you need using the following formula.
如果你知道视野FOV，感应器大小，和工作距离，你能用以下之方程序去计算你所需之镜头的焦距。
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。
Note that it is very important to set the camera film back size correctly if focal length measurements in any units other than pixels are being entered.
请注意，这是非常重要的设置相机的胶片回来大小正确如果焦距测量在任何单位除了像素被进入。
Note that it is very important to set the camera film back size correctly if focal length measurements in any units other than pixels are being entered.
请注意，这是非常重要的设置相机的胶片回来大小正确如果焦距测量在任何单位除了像素被进入。
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