Is my lens broken?

Joined
May 14, 2009
Messages
7
Location
london
Hey

I have recently brought a second hand lens from ebay. It's a 17-35mm Nikkor AF-S.
I have it attached yo my D2X. one thing I have noticed is that if you manually focus the lens seems to zoom a little. in and out. only slightly.

Is this normal for a wide lens such as this? or did I get a dud lens?

Cheers
 
Joined
Jan 15, 2008
Messages
4,553
Do you mean,

a) the zoom ring turns when focusing?
b) the image size in viewfinder changes when focusing?

Option b) is normal for almost all lenses. I am pretty sure all of my lenses do that. One of the ways to "focus" a lens is to actually change the focal length a little, by moving the lens elements further or closer to the sensor.

Some lenses focus solely by extension, meaning that they move all the lens elements in unison. The closer you focus, the farther the lens elements go and the wider the view gets.
 
Joined
Aug 28, 2008
Messages
682
Location
Colorado, USA
I've never had a lens that does this, but could this be what some (K.R. one of them, that's where I heard the term) refers to as "zoom breathing"?
 
Joined
May 14, 2009
Messages
7
Location
london
hey, the zoom ring does not move. It just seems like the image though the view finder changes in perspective a little.

For example; if I frame an object just to the edge of the view finder when I pull through the focus ring the object touches the edge a little.

I'm thinking if I use this lens for video it's going to cause me all kinda of trouble when pulling focus.

It's a pro line nikkor lens. Just wondering if I should send it back or if it's normal.
 
Joined
May 14, 2009
Messages
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Location
london
Hey, Cheers, yeah it looks like it's this.

Now I just need to find out if that's normal with this lens. Either way, it's gonna cause problems when filming .
 
Joined
May 14, 2009
Messages
7
Location
london
Yeah, it's fine for photography, but when I buy my new sony fs100 and try to shoot video with it focus pulling is going to cause the lans to zoom slightly. Therefore not ideal for video.

I suppose it's very minimal so will only be noticeable on really static shots.
 
Joined
Nov 18, 2008
Messages
1,211
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HHI
Yeah, it's fine for photography, but when I buy my new sony fs100 and try to shoot video with it focus pulling is going to cause the lans to zoom slightly. Therefore not ideal for video.

I suppose it's very minimal so will only be noticeable on really static shots.
Am I missing something? The lens appears to be doing what it was designed to do. GH
 
Joined
May 14, 2009
Messages
7
Location
london
well its not designed to have lens breathing, It's just something that happens. I would think that having no lens breathing is more desirable than to have it.

Obviously for video it's defiantly not desirable since you will get zoom when pulling focus.
 
Joined
Feb 5, 2007
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2,722
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Banff National Park, Alberta
I've noticed that most every lens I own has focus breathing, it's just something that the designers never really worried about because until recently most of these lenses would have never been used on video. or at least that's what I'm amusing. I think that every 2.8 lens I own does this to one extent or another.
 
Joined
Nov 18, 2008
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So you bought a still camera lens and expect it to be a movie camera lens? Be glad you didn't buy a 105VR! GH
 
Joined
Sep 15, 2008
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1,413
Location
Sacramento
What the OP is seeing is the normal result of using a varifocal zoom lens. A varifocal lens is a camera lens with variable focal length (zoom lens) in which focus changes as focal length changes. Most, if not all, of the current DSLR zoom lenses are varifocal lenses. Refocusing after/during the zoom isn't a significant problem when shooting still images.

A parfocal lens ("true zoom") remains in focus as the lens zooms and the focal length changes. Most high end movie and video camera lenses are parfocal lenses. As the OP has found out, zooming while video is being actively captured works best with parfocal lenses, since they don't have to be refocused when one zooms in on a subject from a stationary location.
 

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