F 值计算器
F 值 N = 焦距 ÷ 光圈直径。
仅作相对曝光比较。
使用步骤
如何使用
- F 值 N = 焦距 ÷ 光圈直径。
- Choose one unknown and enter the other two positive values.
- Review f-number and relative exposure ratio.
Formula
N = f / D; doubling the f-number reduces geometric aperture area by four, before transmission losses.
Valid domain
Focal length, aperture diameter, and f-number must be finite and greater than 0. 相对曝光比较假定透光率及快门/ISO相同；不是相机测光表。
常见问题
你可能还想知道
Does this measure exposure?
相对曝光比较假定透光率及快门/ISO相同；不是相机测光表。
What is f/2?
An f-number of 2 means the aperture diameter is half the focal length.