How to Get the Most from Cheap Lenses
Let's say Uncle Fred gave us a cheap lens as a present. He probably had no idea what separated a top lens from a cheap lens and figured this one would be great. Then again maybe he's a cheap ass. Regardless, we can probably make good use of the lens with some restrictions. First, let's look into what makes a cheap lens cheap (in order of importance).
- Inferior sharpness
- Pin-cushion, barrel, and moustache distortion
- High levels of chromatic aberration
- Cheap plastic construction instead of high quality plastic or metal
To get the best sharpness shoot at f8 as a general rule. Most cheap lenses are near their sharpest at this f stop. In practical terms, f8 means we need bright scenes - shooting in low light requires lower f stops and sharpness will quickly degrade.
After the shoot, a heavy hand on the sharpening filter in Photoshop, or the use of something like Focus Magic, will often help perceived sharpness. If we're only planning on making small prints or posting shots on the web, it may not matter that much. The lack of sharpness does becomes more evident, though, the larger we blow up the shot.
If Uncle Fred gave us a zoom lens, the second problem is most likely to be worst at the limits of the zoom range. For example, if he gave us a 50-150mm zoom, we prefer to shoot close to 100mm when possible. If we have Photoshop or PTLens, they can help out after the fact. They have tools to help minimize these distortions.
Finally, we have chromatic aberration, or fringing, as it's more commonly called. These can be corrected with Photoshop or PTLens, as well. Both have tools to help minimize fringing. The cheaper the lens the less likely we'll be able to remove all the fringing. Fortunately, fringing is at its worst at the edges of the photo - so shoot a little farther away and crop out the edges!
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