Unverified88% confidenceDecision RuleTime unknown
70-200mm f/2.8恒定光圈是室内运动、婚礼、舞台的标准配置，全程f/2.8保证暗光快门速度；若只拍白天户外，f/4版本可减重约300-500g且画质相近
1
Sources
88%
Confidence
Long-term
Relevance
-
First Seen
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Unverified70-200mm f/2.8属于恒定大光圈'大三元'定位，室内运动、婚礼、舞台、人像抓拍必备；若只在户外白天用，70-300mm f/4-5.6可减重一半并省下大量预算84% similarUnverified室内体育/舞台等弱光运动场景，必须选恒定f/2.8光圈（如70-200mm f/2.8），f/4镜头在1/500s快门下会被迫拉高ISO到6400以上导致画质崩溃82% similarUnverified恒定光圈（如f/2.8、f/4）全焦段进光量不变，测光曝光稳定；浮动光圈（如f/5-6.3）在长焦端光圈缩小，弱光和飞行拍摄时快门速度会掉，打鸟建议至少长焦端f/6.3且机身高感表现好80% similarUnverifiedf/2.8恒定光圈变焦的虚化和进光量约等于f/4定焦，若追求人像浅景深奶油虚化，应直接上85mm f/1.8定焦而非依赖变焦头的2.8光圈78% similarUnverifiedf/2.8恒定光圈超广角比f/4更暗光可用、更能压暗背景做视频，但重量普遍多200-400g、体积明显更大；纯风光白天用f/4三防头足够且更轻便77% similar
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