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| 'Lenses' |
A DSLR or micro System camera is hugely affected by the lens
attached to the front, as the light hitting the sensor impact focus, exposure
and image quality. Be sure to do some research here before you purchase.
Lens Mounts
Each camera manufacturer has their own lens and most aren’t
compatible with one another. If you own a Canon DSLR, for example, you can’t
used Nikon lenses, though you can use independent brands such as Sigma, Tamron
and Tokina – if you get them in the right mount. In the Micro System ranges
Panasonic and Olympus lenses are interchangeable, and as Sony took over Minolta
a few years ago any lenses from the older 35mm system may well work.
Magnification Factor
If you’re migrating from 35mm SLR, your lenses won’t provide the
same field of view on a DSLR unless you have a ‘full-frame’ model such as a
Canon 5D Mark II. Otherwise, for Nikon, Pentax and Sony DSLRs, magnify the
focal length by 1.5x to get the 35mm equivalent.
Maximum Aperture
You pay a premium for lenses with wider maximum apertures, but for
many users they’re worth it. Wider apertures mean you can use faster,
motion-stopping shutter speeds, and shoot handheld in available light with less
camera shake. Zooms whose maximum aperture are fixed throughout the range
(instead of getting smaller as you zoom) also cost more.
35mm Compatibility
Most digital sensors are smaller than 35mm, which is why lenses
designed for digital can be smaller than those designed for 35mm.
Anti-Shake
It’s impossible to hold a camera dead steady without support, but at the faster shutter speeds our shakiness isn’t
noticeable in pictures. As the shutter speed drops pictures become
progressively less crisp until they’re blurry. Optical Image Stabilization
(used by Canon) and Vibration Reduction (used by Nikon) uses a floating element
inside the lens and a gyroscope to cancel out our body movement. It’s effective
enough to give us two or three extra stops of extra shutter speeds to play with
before shake becomes visible. Some cameras use a moving sensor instead, so
IS/VR aren’t necessary.
Built-in Focus Motor
Some lenses incorporate a motor within the lens to drive the auto
focusing, while other are powered by motors within the camera. Lenses with
their own motors will generally focus quicker than those without. Some cameras,
such as the Nikon D60, don’t have a built-in focus motor so you can only use
lenses that have their own. Canon brands its lens motors USM (Ultrasonic
Motor), Sigma call its HSM (Hypersonic Motor) and Nikon’s are called SW (Sonic
Wave).
Compact System Lenses
Just like DSLRs Compact System Cameras have their own, specific lens
system. This also mean the magnification factor is different, as Micro Four
Thirds has a crop factor of 2, Sony is 1.5 and Samsung also has a crop has a
factor of 1.5. All three require image stabilization on the lenses rather than
within the body.
Filter Thread
In order to correct for the magenta haze create by UV light or
create more contrast in a black and white image a screw-in filter can be used.
The thread at the front of the camera will have a diameter, in mm, which will
allow you to attach a variety of filters or adapters to the lens.
Minimum Focal Distance
The distance in cm from the lens front element that it can focus to.
On longer zoom lenses expect this to be over a meter, and in dedicated macro
lenses far lower.
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