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This old Buick seems to have an art deco persona. Getting
in close with a wide-range zoom set to the wide end avoids
having to back up with a longer focal length, which would
complicate the shot due to the car show crowds parading
back and forth between you and your subject.
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It should be fairly obvious
that the main object of using a zoom lens is to avoid having to constantly
change lenses, thereby saving valuable time and missing less pictures
of a fleeting nature. Even if the subject itself isn't going anywhere,
your own time constraints (tours, impatient family and friends, etc.)
can make frequent lens juggling impractical. Besides, on the human nature
side of things, if you have to switch lenses often enough, it's easy to
lapse into "not-a-big-enough-bang" syndrome, passing up shots on the rationalized
justification that it really wasn't that spectacular a shot and therefore
not worth changing lenses. That's a bad habit to get into, because I've
found that many visually "quieter" shots turn out to be the best frames
on the roll, even if it didn't strike me that way at the time.
A few photographers still shy
away from zooms because they've heard they're not as sharp as fixed focal
length lenses. Thirty years ago that was true, but there's no need to
make any excuses for today's better zooms. As with any type of lens, you
pretty much get what you pay for, and that goes for zooms, too. However,
with modern, computer-aided designs, aspheric and hybrid-aspheric lens
elements, low-dispersion glass, etc., sharpness isn't the major concern
anymore. So, if even relatively inexpensive after-market zooms are respectably
sharp, just what is it you're paying for with the more costly models?
To illustrate, let's examine zoom lens characteristics one by one.
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My second, "long" Leica body, equipped with a 90mm lens,
made it easy to grab this nearby contrasting shot of the
quiet ledge pool with the rushing creek in the background,
without the rest of the group I was with having to wait
while I changed lenses. |
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Another approach that I favor
whenever reducing your lens load to the absolute minimum isn't mandatory
is buying a premium-quality zoom that covers the focal lengths that you
use most, and then adding a fixed focal length lens or two to cover the
extreme wide and/or tele ends of the range. I feel that this option maximizes
flexibility and quality; however, there are times (e.g., when being herded
around on an organized tour) when the no-fuss simplicity of one wide-range
zoom is worth any and all minor optical compromises involved. OK, that's
the third time I've said "compromises" without offering any explanation.
The main two factors that are most obvious and that can noticeably affect
your pictures are light falloff at the wide angle end of a zoom's range,
and a variable maximum aperture that becomes progressively "slower" toward
the long end of the range.
The less expensive a lens is,
the more likely it will be to exhibit light falloff in the corners of
wide angle shots, especially at or near maximum aperture; stopping down
a few f/stops helps minimize this effect. As the price goes up, increasing
employment of low-dispersion glass and aspherical lens elements dramatically
improves the evenness of light distribution at wide angle focal lengths.
All extreme wide-range zooms
that I'm aware of have a variable maximum aperture. Most are around f/4.5
or f/5.6 at their longest focal length, which is generally workable. Some
with a really long tele end to their range (300mm and more) top out at
f/6.3 (which is about the slowest maximum aperture that AF systems can
currently work with) or even f/8. On cloudy days, or early or late in
the day, f/6.3 results in a less than sparkling bright viewfinder image.
Keep in mind that this is "wide-open." Stopping down a couple of f/stops
to improve optical performance puts you at f/11-16; add filters and/or
tele-converters and a tripod or ISO 800 film becomes mandatory.
That's why I much prefer a
premium mid-range zoom with a constant f/2.8 aperture throughout its focal
length range. Such lenses exhibit nearly zero falloff at their wide end,
the viewfinder screen remains pleasantly bright, and the use of filters
and slower films presents few problems. Yes, these premium zooms are considerably
larger, heavier, and more costly, but the ease of use and high quality
images produced warrant the higher cost and portability penalty.
Another feature to note is
the focusing/zooming method, especially with manual focus models. Your
choices are "one-touch," whereby you zoom and focus with the same ring,
and two-ring models that control each function separately. At first glance,
the one-touch method might seem the logical way to go, offering faster
operation. However, the most precise way to focus a one-touch, manual-focus
zoom is to zoom out to maximum telephoto (to gain maximum magnification),
focus, then pull the zoom/focus ring back to the desired focal length.
The problem is, that unless you pull absolutely straight back (without
twisting the ring either way), you move off the critical focus point that
you established, something that's easy to do in hectic shooting situations.
Also, some one-touch zooms can creep from the set focal length when aimed
up or down while mounted on a tripod. I therefore prefer a two-ring zoom
for most of my photography. However, with fast, erratically moving subjects
requiring follow focus and follow framing (zooming), a lot of practice
with a one-touch zoom is the more time and motion efficient approach.
The fact that most people never get that good at manual follow focusing
accounts for the current popularity of autofocus cameras.
Be sure to note whether or
not the zoom has a rotating or non-rotating front element. Trust me, you
don't want a rotating front element; they make use of a polarizing filter
and anything other than a round lens shade an impractical nightmare. My
50-250mm Rolleinar zoom, an otherwise fine lens, suffers from this malady
and is seldom used because of it. It was my first zoom lens, and I failed
to check that feature before I bought it; a lesson learned!
Perhaps a wide zoom range,
let's say 28-200mm, appeals to you, but you already have a 28-70mm zoom.
You could, of course, sell your current zoom and buy the 28-200mm, but
there's another option: buy another zoom that starts where your current
one leaves off. In the instance given, you could add a 70-210mm, giving
you a 28-210mm range between them. Whether or not this is a good idea
depends on what your most-used focal lengths are. If, for example, your
two favorite subjects are landscapes and portraits, this two-lens option
is entirely feasible; you'd be using the 28-70mm almost exclusively for
scenics, while the 70-210mm would be a natural for portraits, indoors
or out. On the other hand, if, like many photographers, you tend to have
a couple of favorite focal lengths, say 35mm and 90mm, that you regularly
apply to the same genre of subject matter (e.g., landscapes), then you'd
be constantly switching back and forth between these two zooms, defeating
the whole purpose of this exercise. One last possibility is looking for
a zoom that partially overlaps your current zoom's range enough to include
your most-used focal lengths; otherwise, bite the bullet and buy whatever
zoom that would eliminate constant lens changing, except for really extreme
focal lengths and special-purpose lenses (fisheyes, PC lenses, etc.).
One last consideration for two-zoom outfits: try to make sure they both
accept the same size filters (step-up and step-down adapter rings will
either vignette at the wide settings, or interfere with attachment of
a lens hood).
Incidentally, photojournalists
have for decades been using an abbreviated version of the two-zoom scenario,
carrying two camera bodies, one fitted with a fixed wide angle, the other
with a mild telephoto. Except for Contax's new 35-70mm zoom for their
G2, and Leica's Tri-Elmar, this is the only option for rangefinder users.
Then there's the question of
OEM (Original Equipment Manufacturer) zooms vs. after-market brands. Back
in times BC (Before Computers), the OEM products were most often clearly
superior. Today things have changed, and you need to compare similarly-specified
lenses between your camera brand and the after-market makers such as Sigma,
Tamron, Tokina, Vivitar, etc. Your breadth of choices in AF zooms will
depend on your brand of camera. All after-market makers supply their lenses
in Canon and Nikon mounts; most also offer Minolta and Pentax versions,
but not necessarily with all lenses in their lineups. Each company's (OEM
and after-market) "consumer grade" zooms can vary in quality from model
to model; there are some thoroughbreds and some mongrels, but generally
no "show stock." The premium zooms from both camps include some genuine
optical works of art, and, price permitting, these are the ones that will
make you a truly happy zoom lens convert (if you aren't already). They
tend to be a bit on the heavy side, but not oppressively so.
If you own an older, manual
focus camera (as I do), you'll be grateful (as I am) for Tamron's Adaptall-2
interchangeable mount system. It allows you to fit modern glass to hundreds
of classic 35mm SLRs, including "orphan" brands whose makers have faded
into history. The Tamron lenses illustrated are all Adaptall-2 models;
the 28-200mm and SP 28-105mm f/2.8 LD are also available in AF versions.
I welcomed the opportunity
to compare Tamron's 28-200mm f/3.8-5.6 LD Aspherical and premium SP 28-105mm
f/2.8 LD Aspherical zooms. They both dealt successfully with a wide range
of shooting situations. The SP 28-105mm f/2.8 in particular proved extremely
versatile in capturing near-macro close-ups of vintage car details under
cramped shooting conditions; I can't speak highly enough of this lens'
image quality--it is a definite addition to my wish list. If extended
reach and lighter weight are crucial, the 28-200mm (or AF 28-300mm) may
prove more to your liking. For me, the bright f/2.8 screen image and falloff-free
28mm setting of the SP 28-105mm proved decisive.
So take a long look at the
subject matter that you shoot most frequently, and determine the focal
length range involved. Then compare features and specifications of zooms
available for your camera. Whether it's a AF 24-120mm Nikkor for your
Nikon, a EF 35-350mm for your Canon EOS, an APO 50-500mm from Sigma, or
one of the previously mentioned Tamrons, you should have little trouble
finding a zoom lens tailor-made for your shooting requirements. I have
little doubt that you'll miss constantly changing lenses--and, you'll
miss less pictures!
For more information, contact
Tamron Industries Inc., 125 Schmitt Blvd., Farmingdale, NY 11735; (631)
694-8700; fax: (631) 694-1414; www.tamron.com.
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