What's wrong with my Sigma 135-400mm?

[dRebelXT]

When I lift the lens upside down, the head came out by its
own weight, sometimes when shoot steeper than 75 degrees,
it slips back. I am now zooming by push-pull instead of using
the zoom ring. Am I doing the right thing?

I used it less than 10 times, but saw some dust particles
inside the lens, what shall I do now?

 

[sfhuang]

There's nothing wrong with your lens. That's just the way + quality the lens is built. As for dust inside, it is prob due to the push-pull action of zooming the lens. Inevitable if you ask me unless you don't use it at all.

 

[DEADMETAL]

Zoom creep happens to big and heavy lens. Even on some light lens so it's rather natural

 

[dRebelXT]

Zoom creep happens to big and heavy lens. Even on some light lens so it's rather natural

Thank you, so this is lens creep. What is the term for situations when lens go back & forth
in order to focus on the subject?

 

[Ah Pao]

Thank you, so this is lens creep. What is the term for situations when lens go back & forth
in order to focus on the subject?

That's call "hunting".
E.g. usage: "This lens always hunts in low light, cannot lock focus."

 

[Spectrum]

Zoom creep happens to big and heavy lens. Even on some light lens so it's rather natural

This means louzy design & construction man! Even Nikon AF 70-300mm f/4-5.6 ED lens have this problem too.:thumbsd:

 

[DEADMETAL]

Can't really say it's a lousy design, to have inner zoom, the lens will be way too long for normal storage.

 

[dRebelXT]

What shall I do with the dust particles if I intend to sell the lens?
They appear inside the lens, but not aware of any dust in pictures
though?

 

[besh]

What shall I do with the dust particles if I intend to sell the lens?
They appear inside the lens, but not aware of any dust in pictures
though?

you can "find out" urself,
dust is eveywhere....
and especially in used lens,
no one can prevent that.
i think every used lens should have have some dust or particle inside the lens...
leave it be... it wun affect ur pic quality a lot..
in fact, u can't really feel it