焦距的英文：
focus

参考例句：

Having three focal lengths.
三焦距的有三个焦距的

Focus-to-film distance(f.f.d)
焦点-胶片距离(焦距)

This is a long focus lens.
这是个长焦距镜头。

Adjust the focus of a camera
调整照相机的焦距

The image got out of focus
这影像没有对准焦距。

focusing glass [ screen ]
【摄】调焦距用的毛玻璃

Short focal length (high aperture) lens
短焦距(大孔径)透镜

The image goes out of focus.
这影像未对准焦距。

Eyeglasses having trifocal lenses.
有三焦距镜片的眼镜

The focal length differs with the thickness of the lens
焦距长底随透镜的厚度而变化。

focus是什么意思：
v. （使）集中；（使）聚焦；调节焦距
n. 焦点；焦距；中心

The image is in focus.
这影像在焦点上。

Focus your attention on your work.
把注意力集中在你的工作上。

The research focus of uncommitted robbery has two.
抢劫未遂的研究焦点有二。

The role of this part is to educe the focus of this article.
这一部分的作用是引出本文的重点。

"then focus on the colour of the image, "
接着让他们关注图像的颜色