📷 景深计算器Depth of Field Calculator
根据焦距、光圈、对焦距离和画幅（弥散圆）计算景深：给出超焦距、近点、远点和景深范围，以及对焦点前后的景深分布。对焦距离达到或超过超焦距时远点为无穷远。Calculate depth of field from focal length, aperture, focus distance and sensor format (circle of confusion): the hyperfocal distance, near and far limits, total depth of field, and how it splits in front of and behind the focus point. Beyond the hyperfocal distance the far limit is infinity.
使用说明与常见问题How-to & FAQ
「景深计算器」是什么？What is the Depth of Field Calculator tool?
根据焦距、光圈、对焦距离和画幅（弥散圆）计算景深：给出超焦距、近点、远点和景深范围，以及对焦点前后的景深分布。对焦距离达到或超过超焦距时远点为无穷远。Calculate depth of field from focal length, aperture, focus distance and sensor format (circle of confusion): the hyperfocal distance, near and far limits, total depth of field, and how it splits in front of and behind the focus point. Beyond the hyperfocal distance the far limit is infinity.
如何使用「景深计算器」？How do I use the Depth of Field Calculator tool?
在「景深计算器」中，填写「焦距（mm）」、「光圈 f 值」、「对焦距离（m）」、「画幅（弥散圆）」、「自定义弥散圆（mm）」等参数，结果会随输入实时计算并显示在下方。In the Depth of Field Calculator: Fill in "Focal length (mm)", "Aperture f-number", "Focus distance (m)", "Sensor format (circle of confusion)", "Custom circle of confusion (mm)"; results are recalculated instantly as you type.
景深是怎么计算的？How is depth of field calculated?
先求超焦距 H = f² ÷ (N × c) + f（f 焦距、N 光圈、c 弥散圆）。近点 = s(H − f) ÷ (H + s − 2f)，远点 = s(H − f) ÷ (H − s)，s 为对焦距离（这是薄透镜的精确公式，不是近似式）。当 s ≥ H 时远点为无穷远，景深延伸到无限远；对焦距离必须大于焦距。It first finds the hyperfocal distance H = f² ÷ (N × c) + f (f = focal length, N = aperture, c = circle of confusion). Near = s(H − f) ÷ (H + s − 2f) and far = s(H − f) ÷ (H − s), where s is the focus distance (the exact thin-lens formulas, not an approximation). When s ≥ H the far limit is infinity and depth of field extends forever; the focus distance must be greater than the focal length.
弥散圆（c）是什么？该选哪个？What is the circle of confusion, and which to pick?
弥散圆是人眼可接受的最大模糊圈，取决于画幅：全画幅约 0.030 mm、APS-C 约 0.020 mm、M4/3 约 0.015 mm、中画幅约 0.047 mm。它随画幅和观看放大倍率变化，这里用常见值。The circle of confusion is the largest blur spot still seen as sharp, and depends on the format: about 0.030 mm for full-frame, 0.020 mm for APS-C, 0.015 mm for M4/3 and 0.047 mm for medium format. It varies with format and viewing enlargement; common values are used here.
为什么远点会是无穷远？Why can the far limit be infinity?
当对焦距离达到或超过超焦距时，景深的远端一直延伸到无限远。对焦在超焦距上能让从约 H/2 到无穷远都清晰，是风光摄影的常用技巧。When the focus distance reaches or exceeds the hyperfocal distance, the far edge of sharpness extends to infinity. Focusing at the hyperfocal distance keeps everything from about H/2 to infinity sharp — a common landscape technique.
景深为什么对焦点前后不对称？Why is depth of field uneven front and back?
通常对焦点后方的景深比前方大（约 1:2），距离越远差别越明显，接近超焦距时后方趋于无穷。这是公式的几何结果。The depth behind the focus point is usually greater than in front (roughly 1:2), and the gap grows with distance until the rear becomes infinite near the hyperfocal distance. This follows from the geometry of the formula.
「景深计算器」免费吗？需要注册吗？Is the Depth of Field Calculator free? Do I need an account?
「景深计算器」完全免费，无需注册或安装，打开网页即可使用，手机和电脑都能用；输入的内容只在你的浏览器本地处理。The Depth of Field Calculator is completely free with no sign-up or install and works on phones and desktops; what you enter is processed only in your browser.