Aperture（光圈）

介绍 

相机光圈是镜头内的开口。有些相机具有固定的光圈，而另一些则是可调的。孔径尺寸通常用 \(f\)-值表示，这种表达方式不太直观，因为开口的面积随着 \(f\)-值的减小而增加。 \(f\)- 值 \(N\) 通过以下方式得出：

\[N = \frac{f}{D}\]

其中 \(f\) 是焦距， \(D\) 是入射孔的直径。焦距是从镜头到相机内部焦点F的距离。大多数现代镜头都使用标准的 \(f\)-值，即基于2的平方根的幂相对应的几何数列： \(\frac{f}{\sqrt{2^n}}\) 。这种情况下，这个几何级数每减少一次，相机瞳孔的区域即减少一半。因此，递增或递减该序列即对应增加或减少曝光级数（stops）。

Zivid相机的光圈 

The following table summarizes which Zivid camera families have adjustable (dynamic) aperture and which have a fixed aperture.

Aperture Types by Camera Families
Camera Family	Aperture Type
Zivid 3	Fixed
Zivid 2+	Dynamic
Zivid 2	Dynamic

The relevant models have an integrated electro-mechanical iris that can be rapidly adjusted. A completely open pupil corresponds to an \(f\)-number of \(\frac{f}{1.4}\) and a completely closed pupil to an \(\frac{f}{32}\). To use the stop method, it is recommended to use the following f-number values:

\(f\)-值	\(\frac{f}{1.4}\)	\(\frac{f}{2}\)	\(\frac{f}{2.8}\)	\(\frac{f}{4}\)	\(\frac{f}{5.6}\)	\(\frac{f}{8}\)	\(\frac{f}{11}\)	\(\frac{f}{16}\)	\(\frac{f}{22}\)	\(\frac{f}{32}\)
曝光等级	+4	+3	+2	+1	0	-1	-2	-3	-4	-5