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在摄影领域,光圈是一个非常重要的概念。它决定了通过镜头进入相机的光线量,进而影响到照片的曝光效果。然而,有些摄影爱好者发现,根据光圈公式(f-stop = focal length / aperture)计算出来的口径似乎与实际使用的镜头口径不符。为了解决这个问题,我们采访了一位资深的光学专家和摄影师,希望能为大家解惑答疑。
首先,我们需要明确一个概念,即光圈值(F-stop)并不是指镜头的实际口径大小,而是表示镜头通光量的比例。例如,f/2.8 的意思是,当光圈开到最大时,其通光量是 f/1.4 的一半。因此,即使两个镜头的焦距相同,但由于光圈大小不同,它们所允许的进光量也会有所差异。
其次,镜头的口径并非完全由光圈决定。事实上,镜头口径还包括了卡口部分的大小。通常情况下,单反相机镜头的卡口直径大约为 55mm,远小于光圈口径。这意味着,虽然镜头的最大光圈可能很大,但在实际拍摄过程中,我们很少会使用到如此大的光圈。
最后,我们需要认识到,光圈只是影响照片曝光的一个因素,其他如快门速度、ISO 等参数也会对照片产生影响。因此,在实际拍摄中,我们应该综合考虑各种因素,以获得最佳的曝光效果。
总之,光圈计算公式中的口径并不能直接对应镜头的实际口径,而是表示通光量的比例。同时,镜头口径还包括了卡口部分的大小。在实际拍摄中,我们应综合考虑各种因素,以获得最佳的曝光效果。希望以上内容能帮助大家更好地理解光圈计算公式及其在摄影中的应用。

【来源】https://www.zhihu.com/question/618119984

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