Tried to google around on the saying that "built-in-motor lens focus slower than non-BIM" but couldn't find any valid evidence/explaination.
Actually I have tested some lenses (17-50, 28-75), typically Tamron which has built-in-motor with them. However, I didn't really notice the slow focusing speed (as compared with those without) as claimed by many people.
From my logical point of view, 2 motors (body + lens) will drive something faster than 1 motor, so I really don't have any idea that a BIM lens will focus slower than the non-BIM. Can anyone share the mechanism difference that can truly explain the saying?
Thanks.
P/S: Please don't advise me to just get those lenses that have BIM since I can live with the "slow" focusing, I just want to know the mechanism difference instead of following what people are "circulating".
Actually I have tested some lenses (17-50, 28-75), typically Tamron which has built-in-motor with them. However, I didn't really notice the slow focusing speed (as compared with those without) as claimed by many people.
From my logical point of view, 2 motors (body + lens) will drive something faster than 1 motor, so I really don't have any idea that a BIM lens will focus slower than the non-BIM. Can anyone share the mechanism difference that can truly explain the saying?
Thanks.
P/S: Please don't advise me to just get those lenses that have BIM since I can live with the "slow" focusing, I just want to know the mechanism difference instead of following what people are "circulating".