Sharpness
It is almost never the lens at fault
When you have a blurry or fuzzy picture, it is so easy to blame the lens. After all many reviews compare the sharpness of lenses all the time. Speaking from experience, it is very rarely the lens at fault.
There are a couple of reasons why your image is blurred (opposite of sharp) in order of importance:
- Movement, either you or the object moved during exposure. This creates a blur. You can decrease the exposure time, hold the camera (or the object) still or use a tripod
- Out of focus, not all of your picture is in depth of field due to the aperture and the focus you have. Note that fast lenses may have very small depth of field making it very difficult to keep everything in focus.
- Environment, the light is an important contributor to the sharpness, both direct and indirect (well lit scenes can be exposed faster). Similarly the clarity of the air between the lens and the object will contribute as well. This is especially true for landscape shots using long lenses.
- Diffraction limits is a physical limitation that gets worse with smaller apertures. Basically the problem is that light falling on your pixel will have an airy disc shape and will spill over and contribute to neighboring pixels. This gets worse as you the aperture gets smaller.
- Lenses, they are not perfect and they will create various non-idealities that will contribute to blur your images. Usually the goal is to limit these problems to the edges and corners of the frame. Zooms that cover a wide focal distance range have to optimize many different parameters (cost/weight) and can have issues at various focal lengths.
If you know what the problem is, it is easy to correct
More modern cameras can automatically correct the known distortions for lenses at different focal lengths. Here I use the Nikon 28-200 which at 28mm has very visible distortion. I take two separate pictures, one without any correction the other with Auto distortion control set to on on a Nikon D610.
These pages are for Amateur Photographers and not really for seasoned photographers and professionals. I have no affiliation or commercial interest with any brand/make. I write from my own experience. I ended up using mainly Nikon, so I am more familiar with this brand than others. See price for notes on pricing as well as photography related links.