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— | photowiki:aperture [2023/01/07 15:24] (current) – created ying | ||
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+ | **Exposure** | ||
+ | * http:// | ||
+ | |||
+ | Typical one-half-stop f-number scale | ||
+ | ^f/# |1.0 ^1.2 |1.4 ^1.7 |2 ^2.4 |2.8 ^3.3 |4 ^4.8 |5.6 ^6.7 |8 ^9.5 |11 ^13 |16 ^19 |22 | | ||
+ | |||
+ | How to calculate: | ||
+ | < | ||
+ | |||
+ | One stop down: | ||
+ | sqrt (2) ^ 2 = 2.0 | ||
+ | |||
+ | Hence: | ||
+ | sqrt (2) ^ 1 = 1.4 | ||
+ | sqrt (2) ^ 0 = 1 | ||
+ | sqrt (2) ^ -1 = 0.7 | ||
+ | |||
+ | an f number of 0.95 relates to a stop of -0.148 | ||
+ | sqrt (2) ^ -0.148 = 0.95 | ||
+ | |||
+ | Consider Leica 50mm f0.95 is 10,000 USD, a 0.3 stop slower, | ||
+ | Voigtlander 50mm 1.1 just 1,000 USD, | ||
+ | a 0.5 stop slower Pentax K 50mm f1.2 just 400 USD, | ||
+ | and Pentax M 50mm f1.4 just 100 USD | ||
+ | </ | ||
+ | |||
+ | If **aperture 1 stop larger** (f2 is 1 stop larger than f2.8), **shutter speed** can be **twice faster** (1/25s can be boost to 1/50s) | ||
+ | |||
+ | Thus, get a **35mm f2 prime** lens definitely gives **fast and better performance at night and a All Day walk around purpose** than **28-70mm f2.8** zoom lens. | ||
+ | |||
+ | **Fast and Light-weight is main advantage of Prime Lens**, comparing to fast expensive zoom alternatives. | ||
+ | |||
+ | **Alternative way to create "Large Aperture" | ||
+ | * Bokeh-panorama and Flickr: Ryan Brenizer' | ||
+ | * http:// | ||
+ | * http:// | ||
+ | |||
+ | ====== Bokeh ====== | ||
+ | |||
+ | * https:// | ||