Lens issues...

[bcarlson87]

I have a Sigma 70-300mm f/4-5.6 ...My images aren't sharp when I zoom in (they use to be sharper and I haven't changed any settings). I am wondering if there is anything I can do (Cleaning or Calibrating) to correct this or if I Just need to replace the lens. The lens is about 4 years old and has had A LOT of use.
Thanks.

 

[ac12]

You NEED to give us a LOT more data, for us to work from. Otherwise we are just guessing.

• What are you shooting, stationary or moving subject?
• What physical and lighting conditions are you shooting in?
• Are the lens elements CLEAN, both front and back elements?
• Did you ever drop the lens or knock the lens against something?
• If this is an IS/VR lens, is the IS/VR on?
• What shutter speed are you shooting at?
• What aperture setting?
  
• What distance to the subject?

How about posting a few pictures, with the EXIF data, so we can see what you are talking about.

 

[KmH]

And.
Did you put a 'protection' filter on the front of the lens?
What camera?
Has the lens been dropped or hit hard?
What autofocus mode?
What autofocus area mode?
If OS is on is the camera/lens mounted on a tripod?

Lens don't wear out, though lens elements can get out of alignment. I have a Nikon 80-200 AF-D zoom that was made between 1993 and 1997, or some 20 years ago.