zoom lens on DSLR and compact


mikeeeey

New Member
Jan 27, 2010
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#1
Hope I dont get flamed for asking such questions, again.

Was wondering.

Why is it that in DSLR, when using zoom lens, it extends out. Then when using compact cam like my LX3, zooming in will make the lens retract back.


thanks in advance
 

daredevil123

Moderator
Staff member
Oct 25, 2005
21,662
69
48
lil red dot
#2
Hope I dont get flamed for asking such questions, again.

Was wondering.

Why is it that in DSLR, when using zoom lens, it extends out. Then when using compact cam like my LX3, zooming in will make the lens retract back.


thanks in advance
It has everything to do with lens design. For prosumers and compacts, when adding converters or filters they usually attach fixed length barrel tubes. So, with these tubes, to make sure the lens do not actually hit the attached filter or convertrors, the lens should not extend more. And there is an advantage in retraction during zooming in, is vignette control, especially with that barrel there.
 

Blur Shadow

Senior Member
Sep 17, 2005
4,886
4
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#4
The optical design of the lens will dictate if it will protrude or otherwise. Nothing to do with dSLR/compact.
 

May 5, 2009
480
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16
#5
yea all because of lens design, one of my lens, when i zoom in from wide to tele, actually retract and then protrude out again, i.e. shortest at focal length somewhere in the middle.
 

mikeeeey

New Member
Jan 27, 2010
321
0
0
#6
It has everything to do with lens design. For prosumers and compacts, when adding converters or filters they usually attach fixed length barrel tubes. So, with these tubes, to make sure the lens do not actually hit the attached filter or convertrors, the lens should not extend more. And there is an advantage in retraction during zooming in, is vignette control, especially with that barrel there.
Ahhh.. this make sense. Now I know.. Thanks!!!

But what do you mean by

"And there is an advantage in retraction during zooming in, is vignette control, especially with that barrel there."


I thought with a fixed barrel, lens retracting in will have higher chance of vignetting? why is that an advantage though?
 

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