Nikon CoolPix 4500Nikon updates the hugely successful Coolpix 995, adding a full 4.0-megapixel CCD!<<Viewfinder :(Previous) | (Next): Exposure & Flash>> Page 5:OpticsReview First Posted: 5/29/2002 |
Optics
A Nikkor 4x zoom, 7.85-32mm lens is built into the Coolpix 4500 (the equivalent
of a 38-152mm lens on a 35mm camera), with ten optical glass elements in eight
groups. Maximum apertures range from f/2.6 to f/5.1, depending on the zoom setting.
(The larger effective aperture corresponds to the wide angle focal length.)
Nikon has continued to use the seven blade iris diaphragm first seen in the
995, which gives very fine-grained aperture control, useful for controlling
depth of field, but more so for working with external flash and precisely controlling
the balance between flash and ambient exposure. The contrast-detect TTL autofocus
features an autofocus mechanism with a very fine step size (although Nikon no
longer reports how many AF steps there are), and a working range from 0.8 inches
(20.32 millimeters) to infinity (this includes the macro range). When shooting
in the Auto capture mode, the autofocus remains in the Continuous setting while
using the LCD monitor but reverts to the Single autofocus mode when the LCD
is off (which means you must halfway press the Shutter button to set focus).
However, the Manual capture mode gives you the freedom to choose between Continuous
or Single autofocus, regardless of LCD status. The Continuous focus mode results
in the lens continually "hunting" for the best focus as you move the
camera around, settling down when the camera and/or subject stops moving. Autofocus
tracking speed isn't terribly high (mentioned in case you were expecting pro-level
AF tracking as on Nikon's F5 film camera), but the Continuous AF option definitely
helps with moving subjects. The downside is that it burns more battery power
than Single AF mode.
You can manually adjust focus by holding down the Focus Mode button and turning
the Command dial. A distance scale appears in the LCD monitor, with an adjustment
bar that stretches from macro to infinity positions. For some reason, Nikon
has chosen not to provide a numerical distance readout, which can be very helpful
in setting manual focus. The Focus Confirmation option (selected via a setup
menu entry) snaps the LCD monitor into exaggerated sharp focus when the lens
is properly focused. This is very helpful for setting focus manually when you
can see your subject clearly, but it would still be helpful to have a distance
readout for those times when you cannot. (Nighttime candid and wildlife photography
are both situations where I've found an explicit distance readout helpful.)
The 4500's autofocus mechanism employs the same sophisticated zone-sensitive
system from previous Coolpix models, featuring several operating modes. It has
five possible focus zones (center, top, bottom, left, right), useful for achieving
accurate focus on off-center subjects. The Focus option under the settings menu
allows you to choose modes in which the camera chooses the focus zone automatically,
or in which you can explicitly select the focus area you want to use (a nice
feature that works well when combined with the spot metering mode, which can
likewise be directed to determine exposure from the same five zones). In the
"Auto" option for focus area selection, the camera chooses the area
corresponding to the object closest to the camera. When the area focus option
is set to Off, the camera bases focus on the central AF area. (One Playback
mode information screen displays a focus area overlay, and shows which focus
area was chosen for each image, by highlighting the appropriate set of marks
in red.)
The lens itself has the same 28mm filter threads as the preceding Coolpix models,
which accommodate the full range of Nikkor accessory lenses for wide-angle,
telephoto, macro, and fisheye focal lengths, as well as a slide copying adapter.
Once an accessory lens is attached, you'll need to select the corresponding
lens type in the lens settings menu. (The camera adjusts its operation for different
lens types by restricting the zoom range to avoid vignetting, switching to center-weighted
metering for the fisheye adapter, etc.)
The 4500's digital telephoto feature is enabled through the Zoom option under
the Setup menu, and enlarges images up to 4x. An indicator on the LCD monitor
displays the range of digital zoom at each step (from 1.1x to 4.0x). Keep in
mind that digital telephoto only enlarges the center of the image, resulting
in reduced resolution as more digital zoom is used. The camera automatically
switches to center-weighted metering and the center autofocus target when digital
zoom is active. Also under the Zoom option, you can set the startup position
of the lens (either wide or telephoto) and activate the Fixed Aperture function,
which keeps the aperture fixed as the lens zooms.
This looks like the identical lens used on the 995, so it should come as no
surprise that it has very similar optical characteristics. (Although the focal
length range is listed by Nikon as being very slightly different: 7.85-32mm,
vs 8-32mm on the 995.) Geometric distortion is a bit high at the ends of its
zoom range, showing 1.04% barrel distortion at wide angle, and 0.53% pincushion
at telephoto. Chromatic aberration is about average, showing about 5-6 pixels
of color around high contrast objects in the corners of its images.
Macro fans will be pleased to learn that the 4500 is every bit a Coolpix in
that category: Its minimum macro coverage area is approximately 0.84 x 0.63
inches (21.2 x 15.9 millimeters)
Perspective Correction
This is more of a post-exposure sort of thing, but its effect is decidedly "optical,"
so I opted to include it in the Optics section of the review. One of the attractions
of digital photography is that you can manipulate the images on your computer
after the fact, to correct deficiencies in the original shot. A common problem
with essentially any camera other than a professional "view" camera
has to do with perspective distortion. When you tilt your camera up to snap
a photo of a tall building, perspective makes the vertical lines of the building
converge, giving the appearance that the building is leaning backward. This
effect is quite easy to correct on a computer, but a lot of users will lack
the software needed to do so. On the 4500, Nikon's built a perspective-correction
function into the playback menu, so the camera can perform a limited amount
of perspective correction on its own. This is the first I've seen of an advanced
image processing function like this on a digicam, but I won't be surprised if
we see more such in the future. To use this function, you call up the photo
you want to correct in playback mode, select "Perspective Control"
from the playback menu, and the press the Multi Function lever up or down to
vary the effect. When you've got things the way you want, press the lever to
"set" the function, and wait while the camera makes a new copy of
the photo with the correction applied. (The original image is left unchanged.)
Pretty slick! This clearly won't eliminate the need for programs like Adobe's
Photoshop(tm), but it's a neat feature I've not seen before in a digicam.)
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