Why can’t lens choice be straightforward?

Started Mar 30, 2013 | Questions thread
Guidenet Forum Pro • Posts: 15,748
Re: Why can’t lens choice be straightforward?

All macro lenses are going to be a little slower to focus than many other lenses. Think about the reasons. It has to consider a range from 1:1 lifesize all the way to infinity and back. Non-macro lenses only have to consider from their closest point to infinity. It is one reason macro lenses often have focus limiter switches on them to limit their range when not doing macro work. This helps but there's another reason.

Macro lenses often have a more granular level of focus gearing. Where it might take some lenses a mere quarter turn to focus from close to far, a macro lens might take three or four times that amount. It's on purpose so when you're doing macro in manual focus, you can more accurately attain perfect focus. The down side is a slower focus in every day non-macro use.

Couple reason one and two and it's pretty impossible to design the lens to keep up with the speed of non-macro gear. You have to understand this trait and work around it. Use the focus limiter and try to prefocus on the subject. Also make sure the lens has a sonic ring type focus motor. It's one thing I like about Sigma's macro lenses. They have the HSM motors in some of them. It won't make a macro lens blazingly fast, but it helps a little.

Take care.

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Cheers, Craig
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