방송용 카메라의 경우 front focus ring과 back focus ring이 존재하는데
back focus ring을 조절하면 zoom in/out 시에도 촛점을 놓치지 않고 잘 잡는 듯?
[링크 : https://www.youtube.com/watch?v=qIYvYvkblMs]
[링크 : http://nofilmschool.com/2011/12/set-backfocus-video-camera]
[링크 : https://www.youtube.com/watch?v=28NPkAJGC6s]
If you find that your focus is sharp when you are zoomed in but soft when zoomed out, your back focus needs adjusting. This normally only happens to cameras with detachable lenses — consumer-level camera users shouldn't have to worry about it.
Technical Note: Back focus refers to the "focal flange length". This is the distance between the rear lens element and the CCD.
[링크 : http://www.mediacollege.com/video/camera/focus/back-focus.html]
[링크 : https://www.videouniversity.com/articles/adjusting-the-back-focus-of-a-lens/]
물론 back focusing과 front-focusing은 촛점을 잡을때 심도에 따른 구분인걸로.. back focus와는 또 다른 용어 같고...
Back-focusing and front-focusing is when the auto-focus consistently is slightly off in either direction.
[링크 : http://photo.stackexchange.com/questions/900/what-is-back-focusing]
inner focus 는 또 다른 용어 같은데.. 어렵네..
An internal focus lens (sometimes known as IF) is a photographic lens design in which focus is shifted by moving the inner lens group or groups only, without any rotation or shifting of the front lens element.
[링크 : https://en.wikipedia.org/wiki/Internal_focusing]
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BD-KA237_KA217.pdf
