Do you disregard lens test data because it's too complicated? Andrew Smallman explains how you can more effectively and easily test your lens to determine how good it is.
You’ll never make a really good photo if your camera doesn’t already have a good lens on it. Quite simply, the image quality potential of any camera begins with, and is determined by, its lens. Small wonder that so much attention is given to discussing, testing and comparing lenses on internet review sites and forums. But there are problems with the information provided on these sites. In many cases test results are presented in a highly technical format which can be difficult for most of us to understand. Testing methods and terminology also aren’t consistent across different sites, which makes any comparison virtually impossible.
External Inspection
Of course you want to know how the lens on your own camera performs. New or used, old or recently made, it might have been damaged, have an assembly fault or indeed some other issue. Your test process should begin with an inspection. Check for scratches, dents, marks or other signs of damage. Remove any filter and look carefully at the glass. If there’s a lot of dust, you should clean the front and rear elements with a hand puffer (not compressed air) and/or a specifically designed lens cloth (to avoid scratching). A few bits of dust inside the lens will have no appreciable effect on image quality, but any sign of cloudiness or fungus most certainly will.
Note whether a zoom lens is a parfocal (true zoom) or varifocal type. Most kit and budget zooms are of the varifocal type, which means they change focus when zoomed. These lenses lack a distance scale and must be re-focused after zooming. True zooms usually do have a distance scale. They’re more complex and expensive to make and will stay in focus with zooming.
Mount the lens on your camera and work the zoom and focus rings. Note any roughness or stickiness. Operate any switches on the lens barrel and check that each actually performs its intended function. Look into the lens while making an exposure at a small aperture to check the diaphragm is working. To check if any optical image stabiliser is functional, zoom the lens out and look through the viewfinder with image stabilisation off, then on. You should be able to see the image steady with OIS on. Also check that the auto-focus and manual focus are operating...
ALSO IN THIS ISSUE: Reviews on the latest multi-purpose zooms; Christmas Gift Guide; Photo trekking - The Overland Track, Tasmania; Locations: Northern Grampians, Vic; Panasonic Lumix G3