一、像距和物距、焦距的关系:
焦距 | 物距 | 像距 |
25mm | 3m | 25.21mm |
50mm | 3m | 50.85mm |
50mm | 5m | 50.51mm |
50mm | 7m | 50.36mm |
75mm | 7m | 75.81mm |
①在照相机中,像距远远小于物距(或物距远大于焦距、物距大于2倍焦距),像距略大于焦距;②焦距不变时,物距越大则像距越小;③物距不变时,焦距越大则像距越大。
二、像的大小与物距、焦距的关系(假设物体高1m):
焦距 | 物距 | 像高 |
25mm | 3m | 8.4mm |
50mm | 3m | 16.9mm |
50mm | 5m | 10.1mm |
50mm | 7m | 7.2mm |
75mm | 7m | 10.8mm |
①在照相机中,物距和焦距都相同时物越大则像越大(无法从上面数据中看出);②焦距不变时,物距越大则像越小;③物距不变时,焦距越大则像越大。
三、视角与焦距的关系(对35mm照相机):
焦距 | 视角 |
6mm | 220° |
10mm | 180° |
25mm | 82° |
50mm | 47° |
75mm | 16° |
100mm | 12° |
600mm | 4°1′ |
对同一照相机,焦距越大视角越小。
四、景深(35mm照相机,弥散圆半径0.025mm,灰色格表示超景深)
焦距 | 物距 | 光圈 | 景深范围 | 景深长度 |
25mm | 3m | 4 | 2.03m~5.73m | 3.69m |
25mm | 8.25m | 4 | 4.12m~∞ | ∞ |
50mm | 3m | 4 | 2.68m~3.4m | 0.72m |
50mm | 3m | 5.6 | 2.57m~3.6m | 1.03m |
50mm | 3m | 8 | 2.43m~3.93m | 1.5m |
50mm | 5m | 4 | 4.17m~6.25m | 2.06m |
50mm | 5m | 5.6 | 3.91m~6.94m | 3.04m |
50mm | 5m | 8 | 3.58m~8.28m | 4.7m |
50mm | 7m | 4 | 5.48m~9.7m | 4.22m |
50mm | 7m | 5.6 | 5.02m~11.5m | 6.51m |
50mm | 7m | 8 | 4.5m~15.8m | 11.3m |
50mm | 32.9m | 4 | 16.5m~∞ | ∞ |
50mm | 23.3m | 5.6 | 11.7m~∞ | ∞ |
50mm | 12.6m | 8 | 9.25m~∞ | ∞ |
75mm | 7m | 5.6 | 5.96m~8.48m | 2.51m |
75mm | 7m | 8 | 5.62~9.49m | 3.67m |
75mm | 37.1m | 8 | 18.5m~∞ | ∞ |
对同种底片,①物距和焦距不变时,光圈越大景深越小;②物距和光圈不变时,焦距越大景深越小;③焦距和光圈不变时,物距越大景深越大。
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