[marisalwy]

Someone has complained of LB6 in DC Fever as follows:

缺點：貴小五好多，
對小六好失望，原來唔足２００mm，真係要問一問Nikon點解會咁，
正確黎講D支鏡唔係70-200vrll，係70-180vrll，唔道左D買家就唔好啦！！
中心成像個人感覺唔夠小五咁利

感受：用apsc機既用家可以唔駛買，浪費金錢，
依家好後悔賣左支小五出去，仲要補多幾千，
就係為升班而升班，都唔知為乜！！！

* * * * * *

This phenomenon is called "focus breathing". Please refer to this link about "focusing breathing" of telephoto lenses:

http://www.bythom.com/nikkor-70-200-VR-II-lens.htm

LB5 is a slight breather (actual focal length is 182 mm, for 200 mm zoom setting at close focus)

LB6 is a heavy breather (actual focal length is 134 mm, for 200 mm zoom setting at close focus)

[marisalwy]

算不算是呃稱（不足稱）？

[whispermakers]

算不算是呃稱（不足稱）？

===============================================
唔算, 其實好多文都講過, 變焦鏡既focal length係以對焦點係 '無限遠' 計既.
即係當你用200mm, 而對焦點係 '無限遠' 時, focal length就係200mm.
一般來講當對焦點愈近, 所得到既focal length就會愈短, 正如marisalwy 兄所講, 當lb6用最近對焦距離既時候, 200mm大約只係有134mm既focal length, 情況係點要視乎支鏡既設計.
Besides, "中心成像個人感覺唔夠小五咁利", 好多測試都已經好清楚講到lb6係比lb5中心成像只係好少少, 而lb6比lb5既最大改進係中心同邊位成像既落差少左--即係邊位既解像高左

[marisalwy]

Thanks for whispermakers C-hing's explanation!