Why the 70-200mm is so popular for portraiture:
* 圧縮： これは大きなものです。 Longer focal lengths compress perspective, making features appear more flattering and less distorted. It minimizes the appearance of a large nose or prominent forehead, leading to a more pleasing result.
* バックグラウンドブラー（ボケ）： 70〜200mmのレンズ上の長い焦点距離と通常、広い開口部（f/2.8またはf/4）は、浅い深さの深さを可能にし、被験者を分離する美しくクリーミーな背景のぼかしを作成します。 This is a signature look of professional portraits.
* 作動距離： あなたはあなたの主題からさらに離れることができます、それは彼らがより快適で自己意識の少ない気分にさせ、より自然な表現につながることができます。 It also allows you to fill the frame without getting uncomfortably close.
* 汎用性： While primarily a portrait lens, it can also be used for other genres like sports, wildlife, and event photography. It's a useful all-around lens to have in your kit.
* 画質： 70-200mm lenses are typically built to a higher standard than other lenses, offering excellent sharpness, contrast, and color rendition.
Why you *don't* *absolutely* need one:
* Alternatives Exist: You can achieve good portraits with other lenses, such as:
* 50mmレンズ： Often called the "nifty fifty," a 50mm is affordable, fast, and can produce excellent portraits. You'll need to get closer to your subject.
* 85mmレンズ： A popular choice specifically designed for portraiture. 圧縮と作動距離のバランスをとることができます。 Often considered the sweet spot for portraiture.
* Zoom Lenses (e.g., 24-70mm, 24-105mm): While not as specialized, these can be versatile and cover some of the focal lengths useful for portraits. You'll need to be mindful of distortion at the wider end and may not get as much background blur as with a 70-200mm.
* Crop Sensor Cameras: Using a 50mm or 85mm lens on a crop sensor camera will effectively give you a longer focal length due to the crop factor. This can make them more suitable for portraits.
* コスト： 70-200mm lenses are generally expensive, especially those with a wide aperture (f/2.8). If you're on a tight budget, you might want to explore other options.
* Weight and Size: These lenses are often heavy and bulky, making them less ideal for travel or street photography.
Here's how to decide if a 70-200mm lens is right for you:
* What is your budget?
* What style of portraits do you shoot? If you prefer environmental portraits, a wider lens might be more appropriate. If you focus on headshots and tight portraits, a longer lens is ideal.
* What kind of subjects do you photograph? If you photograph children, the extra working distance can be invaluable.
* How important is background blur to you?
* Are you willing to invest in a heavy and bulky lens?
要約：
厳密には必要ありませんが、70〜200mmのレンズは、優れた圧縮、バックグラウンドブルール、および作動距離を提供するポートレートカメラマンにとって非常に価値のあるツールです。ただし、それは多大な投資であり、他のレンズは特に予算がある場合や別の射撃スタイルを好む場合、優れた結果をもたらすことができます。 Consider your needs and budget before making a decision. Renting a 70-200mm to try it out before buying is also an excellent idea.