How To Evaluate Your Camera Lenses?

By Author: Josh Wilson
Total Articles: 2
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Camera Lenses is an essential part of professional photography that adds an extra edge to your photographic skill. Manufacturers and shop owners usually claims that their lenses is the sharpest among all. But how does a person come to know whether the lens is truly sharp or not and is sharpness is the only criteria of judging a lens.

There are various aspects, based on which the quality of lens should be judge. Let’s go one by one.

SHARPNESS: It is mostly about contrast. Now for testing the sharpness put a piece of newspaper on the wall and illuminates it with two high powers – evenly-dispersed lights, one on each side. Mount your camera on a tripod and make an exposure of the newspaper using autofocus. Use as fast shutter speed as you can for the light conditions and open the lens all the way to its widest aperture. Then make on exposure at each aperture and look at the results.

See how sharp the text in the newspaper appears at a 100% enlargement. Pay particular attention to sharpness at the center of the frame versus the edge of the frame. Even bad lenses are typically somewhat sharp at the center ...
... but perform poorly at the edges. Look at the results for each aperture. They will be different.

LENS SPEED: Lens Speed plays an important part when you need good low light performance. But beside this it can also be an indicator of a high quality lens. Most manufacturers put their best glass into their fastest lenses. If you have the money and want the best, buy fast lenses. Also, note that zoom lenses with constant apertures tend to out-perform variable aperture zooms where the lens speed changes with the focal length.

MINIMUM FOCUS DISTANCE is important, but because only you know how close you will be to your subjects, only you know how much or how little minimum focus distance you need. Higher quality lenses tend to have closer minimum focus distances, but not always. To test a lens’ minimum focus distance, use a tape measure between the focal plane and the subject. Usually the manufacturer’s estimates are close, but not always.

LENS ELEMENT quality is critical to lens performance. Generally, we should look for the lenses with Apochromatic and Aspherical elements which reduce distortion, and add contrast and sharpness. The more of these types of elements in your lens will be, the better performance you can expect. Of course you will have to trust the manufacturer on this point since you can’t take the lens apart to see for yourself.

LENS FLARE is more than little star-shaped rectangles appearing in backlit pictures. Lens flare is often unseen or unnoticed in the viewfinder. Its impact is to reduce contrast. Even when you don’t see a starburst, you may be the victim of lens flare if you use inexpensive lenses. Pro lenses have coatings to reduce lens flare and may even include special lens hoods also designed to reduce flare.

CHROMATIC ABBERATION is color fringing or halos around high contrast objects. It makes pictures look soft and is more prevalent in lenses without LD glass. It’s also easier to spot at wide apertures than smaller apertures.

LENS CONSTRUCTION AND BUILD STANDARDS will help you in deciding whether or not the lens seems likely to last under day-to-day use. Cheap plastic lenses are more likely to fail than magnesium lenses. Lenses with solid metal lens mounts will not warp as will plastic lens mounts. Sealed lenses will not be as likely to suffer damage from dust and moisture as unsealed lenses.

FOCUSING SPEED can be critical to some types of photography. Most 35mm camera lenses are auto focusing. We usually want one that acquires focus quickly and accurately. To test this, shoot the types of objects you normally photograph with the lens you are testing. Have someone next to you with a stopwatch. Set your camera to beep when focus is acquired. Ask them to watch you press the shutter and start the stop watch. Stop the watch when you hear the beep. Measure the time between the shutter press and the beep and you now know the time it took to acquire autofocus. The less time the better.