Using VR Lenses
Using VR Lenses
Nikon has an impressive list of lenses offering
Vibration Reduction, including the
18-55mm and 55-200mm kit lenses that are
available with the D60. This VR technology
is used to combat image blur caused by
camera shake that occurs, especially when
handholding the camera at long focal
lengths. The VR function works by detecting
the motion of the lens and shifting the internal
lens elements. This allows you to shoot
up to 3 stops slower than you would normally.
If you’re an old hand at photography,
you probably know this rule of thumb: To
get a reasonably sharp photo when handholding
the camera, use a shutter speed
that corresponds to the reciprocal of the
lens’s focal length. In simpler terms, when
shooting at a 200mm zoom setting, your
shutter speed should be at least 1/200 second.
When shooting with a wider setting,
such as 28mm, you can safely handhold at
around 1/30 second. Of course, this is just a
guideline; some people are naturally steadier
than others and can get sharp shots at
slower speeds. With VR enabled, you should
be able to get a reasonably sharp image at
a 200mm setting with a shutter speed of
around 1/30 second.
Although the VR feature is good for providing
some extra latitude when shooting with
low light, it’s not made to replace a fast
shutter speed. To get a good, sharp photo
when shooting action, you need to have a
fast shutter speed to freeze the action.
Remember, when shooting in low light the
VR only compensates for camera movement,
so if your subject moves even slightly the
image will be blurry.
Another thing to consider with the VR feature
is that the lens’s motion sensor may
overcompensate when panning, causing the
image to actually be blurrier. So, in situations
where you need to pan with the subject,
you may need to switch off the VR. The
VR function also slows down the AF a bit, so
when catching the action is very important,
you may want to keep this in mind as well.
While VR is a great advancement in lens
technology, few things can replace a good
exposure and a solid monopod or tripod for
a sharp image.
Lens Distortion
Lens Distortion
When dealing with any kind of lenses you eventually have to deal with optical distortion.
The lenses you attach to your camera are a complex system of optics with
many different lens elements that are used to give a certain field of view. Without getting
into the technical details of how a lens works, just know that the lens elements
bend or refract the light manipulating it to magnify it (in the case of a telephoto) or
making it look farther away (in the case of wide-angle lenses). With all of this light,
bending going on, lenses can distort the image-making it look different than the original
subject.
Each type of lens has its own different kind of distortion. For example, wide-angle
lenses suffer from what is known as barrel distortion. Barrel distortion is characterized
by the image being sort of rounded out near the edges of the frame. You can see
in the following figure that the parallel lines at the edge of the image bulge outward.
Telephoto lenses suffer from the opposite problem, which is referred to as pincusion
distortion. This type of distortion is characterized by the edges of the frame appearing
to be pinched in toward the center, as you can see in the figure with the parallel
lines at the edge of the frame bending toward the center.
Both types of distortion are more noticeable near the extreme edges of the frame.
Almost all lenses manufactured today are rectilinear, which means that there are
additional lens elements built into the lens that rectify, or fix, the curved lines. In
wide-angle lenses these elements are sometimes referred to as aspherical. Although
these lens elements are designed to counteract the curvature, no lens design is perfect,
so there will always be some lens distortion, although it is usually minimal.
Fisheye lenses are lenses that have not been corrected for any type of distortion and
the images appear curved or spherical.
Most lens distortion is only noticeable when photographing subjects that have a lot
of straight lines, especially near the edges of the frame, so lens distortion is not
always a problem. However for those times when you may be photographing images
with a lot of straight lines and distortion may be noticeable, some image-editing programs
such as Nikon Capture NX and Photoshop CS3 have tools that allow you to correct
for the distortion.
Normal Lenses
Normal Lenses
A normal lens approximates the field of
view of the human eye. In the past, with
35mm film cameras, the normal lens focal
length was 50mm. dSLR cameras have a
sensor that is smaller than a frame of 35mm
film, so the normal lens focal length has
shortened to a range from 28 to 35mm to
accommodate for the smaller sensor size.
Sigma 30mm f/1.4 EX DC HSM lens
Normal lenses are very versatile and can be
used in a variety of shooting situations.
Everything from landscapes to portraits can
be photographed using a normal lens with
very good results.
Most cameras today usually come equipped
with a zoom lens that encompasses a wideangle
to short telephoto zoom range (such
as the D60’s 18-55mm) that has the normal
focal length somewhere in between the
wide and telephoto settings, but a good 28
or 35mm prime lens can be found relatively
inexpensively. And, either of these prime
lenses is lighter and usually has a faster aperture
than a common zoom lens. Therefore,
one of these lenses can be very useful if you
need to pack light or if you are shooting in
low-light conditions
