Sony 18-70mm f/3.5-5.6 and Carl Zeiss Vario-Sonnar T* DT 16-80mm
f/3.5-4.5
by Bob Atkins; created November 2007
This article compares two wide-to-telephoto zoom lenses for Sony
digital cameras.
The first is the Sony 18-70mm f/3.5-5.6, often supplied as a kit lens with
the Sony Alpha A100. The second is the Sony Zeiss Vario-Sonnar T* DT 16-80mm
f/3.5-4.5, which
has a similar zoom range but is about four times as expensive.
Both of these zooms are designed for the APS-C sized sensor in the
Sony A100 (and A700).
Because their image circle is smaller than that of full frame lenses,
they cannot be used on
earlier Konica-Minolta film SLRs.
Left: Sony 18-70mm f/3.5-5.6 Right: Sony Carl Zeiss Vario-Sonnar
T* DT 16-80mm f/3.5-4
.5
The 18-70mm and the 16-80mm are fairly similar in size as shown
above, although the Zeiss 16-80 is twice as heavy (15.5oz vs. 8.3oz)
and seems sturdier. Both have a useful zoom range for general-purpose
work and yield images of good quality and contrast. However, the more
expensive 16-80 lens does have a slightly larger zoom range, keeping
in mind that 16mm provides significantly wider coverage than 18mm.
The 16-80 has the same effective coverage as a 24-120mm zoom would on
a full frame camera, while the 18-70 has the effective coverage of a
27-105mm on full frame. Lenses with this range are suitable for travel
photography and are a staple for wedding photographers, but are not
long enough for sports or wildlife.
Both lenses have a maximum magnification of obout 0.25x, which
means you can fill the frame with an object as small as 63mm x 95mm
(2.5" x 3.75"). The 16-80 has a distance scale marked in feet and
meters, while the Sony 18-70 lacks any external indication of focus
distance. In practice the lack of a distance scale is unlikely to be
of concern to most users of the 18-70. Both lenses are supplied with a
lens hood, but as you can see from the photo above, the 16-80 hood is
a deeper "petal" design and is more efficient at shading the lens from
stray light.
The A100 body recorded the 18- 70
lens identity in the image EXIF data correctly, while the 16-80 was
recorded as "unknown lens". If there are any more lenses in the Sony
line that can't be identified by the bodies, this could cause
confusion this didn't cause any problems for these tests since
I was only using two lenses, it could potentially cause confusion for
someone using multiple lenses, especially if more than one was not
identified in the EXIF data.
Image Quality
While the quality of the images from both lenses was generally quite
good, if you look closely,
you can see that the image quality of the more expensive 16-80 lens is
higher, particularly
when you look at areas away from the center of the frame. This can be
seen in the 100 percent
image crops shown below.
The areas outlined in yellow and red are shown in more detail below
for each lens set to
around 30mm and images captured wide open (f4 for the 16-80, f5 for
the 18-70) and stopped down
by about one stop.
In the center of the frame all the images look pretty good. Those
taken using the
16-80 were slightly sharper than those taken using the 18-70 kit
lens.
The differences are easier to spot closer to the edge of the
frame. Here the 16-80
shows its superiority by producing a sharper image than the 18-70,
even with the 18-70
lens wide open and stopped down to f8.
Both lenses showed visible barrel distortion at their widest
setting. Distortion was reduced at longer focal length settings,
becoming slight at 35mm (particularly for the 16-80) and negligible at
the maximum focal length. Note that barrel distortion can be
corrected with digital post-processing. Chromatic aberration was well
controlled in both lenses and would be unlikely to be a problem.
Conclusion
You get what you pay for and what you're willing to carry in terms of
weight. The more expensive and heavier lens delivers substantially
better image quality. Both lenses are too slow for use indoors in
available light, especially given the mediocre performance of Sony
digital bodies at high ISO settings.
Alternatives
For a low-light zoom lens, consider the
Tamron 17-50mm f/2.8 XR Di II LD for Sony, $430, which requires only one fourth
as much light as the 18-70 kit lens. The
Sigma 30mm f/1.4 EX DC for Sony and Minolta, $420, requires only one sixteeth as much light
as the kit lens and provides a fixed normal perspective.
Where to Buy
Amazon.com has the Sony 18-70mm f/3.5-5.6 DT, $160 (review), and the
Sony 16-80mm f/3.5-4.5 DT Carl Zeiss, $700 (review),
in stock and offers free shipping on both lenses.
Specifications
| Lens |
Sony
18-70/3.5-5.6 |
Zeiss
16-80/3.5-4.5 |
| Focal Length (35mm equiv.) |
18 - 70mm (27-105mm) |
16-80mm (24-120mm) |
| Minimum Aperture (wide - tele) |
f22 - f36 |
f22 - f29 |
| Filter Size |
55mm |
62mm |
| Distance Scale |
No |
Yes (ft/m) |
| Minimum Focus Distance |
15" (0.38m) |
13.8" (0.35m) |
| Maximum magnification |
1:4 (0.25x) |
1:4 (0.25x) |
| Aperture blades |
7 |
7 |
| Groups/Elements |
9/11 |
10/14 |
| Length |
3" (77mm) |
3.4" (83mm) |
| Diameter |
2.6" (66mm) |
2.8" (72mm) |
| Weight |
8.3oz (235g) |
15.5oz (440g) |
More
Sample Images with the 18-70 and the 16-80
Original text and images ©2007 Bob Atkins
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, April 23, 2008; 09:19 A.M. 
