In this week's video tutorial you will learn about the various benefits of processing your RAW files in an editing program. Paired with the advantages of shooting in manual mode, this important step...
If you want one lens to "do it all", with a 13.9x zoom
range, the Tamron 18-250/3.5-6.3 beats the 28-300mm (10.7x) and
18-200mm (11.1x) competitors by a significant margin. When used on an APS-C
DSLR, such as a Canon Digital Rebel XTi (Black) (review), the Tamron
18-250/3.5-6.3 is equivalent to a 29-400mm lens on a full frame
the wide zoom range, the Tamron 18-250/3.5-6.3 is quite a small lens, measuring only
2.9" in diameter and 3.3" long and weighing 15.2 oz. It's a
DiII series lens, which means that the image circle covers only the area of APS-C sized
sensors and thus is incompatible with 35mm film cameras and full
To improve image quality the Tamron 18-250 uses two hybrid aspherical elements,
one AD (anomalous dispersion) element and two LD (low dispersion) elements. The $499 price
of the lens includes a hood and a six year warranty. It is available in the following versions:
When is it most valuable to have a wide-range zoom and not be forced
to carry or change lenses? Travel and dusty environments are the most
common situations. If you don't change lenses, you're much less
likely to get dust on the digital sensor.
The 18-250mm focal length range sounds useful for everything from
landscape work to portraits, sports, and wildlife photography.
Unfortunately, the relatively slow aperture in the portrait range
(f4.5 at 50mm, f5.0 at 70mm) means that a distracting background will
be rendered in sharper focus than with a faster prime lens such as the
Canon EF 50mm f/1.8 II, (compare prices) (review). For sports photography, the slow
aperture means that you won't be able to use the fast shutter speeds
required to freeze action, unless you set the camera to ISO 800 or
higher, which reduces image quality. For wildlife, the slow aperture
means that you'll need a tripod, especially given the lack of image
stabilizer in the lens.
At the telephoto end of the range, in particular, the slow maximum
aperture and the lack of image stabilization makes this a lens that
will perform best outdoors in bright light.
The maximum aperture is f3.5 at 18mm, dropping to f4.0 at 35mm, f4.5 at
50mm, f5.0 at 70mm, f5.6 at 100mm and f6.3 above 200mm.
The quality of the images from the Tamron lens were similar to those
from the Canon 17-85.
At the widest setting, barrel distortion and vignetting are
noticeable. Both lenses were sharp in the center, with softening at
the edges. Edge quality improved with both lenses by closing down the
aperture one or two stops. Distortion from the Tamron 18-250 was very
low by 28mm. Vignetting, or darkening of the images at the corners,
was reduced significant by closing down the aperture by one or two
In the 100-250mm telephoto range center sharpness of the Tamron lens
was good, even wide open, though "wide open" is only f6.3
from 200-250mm. Image quality dropped off at the edges of the frame
due to lower sharpness and chromatic aberration. Stopping down to f8
improved edge sharpness slightly. In comparison, images from the
Canon EF 70-300mm f/4-5.6 IS USM
were sharp in the center and at the edges. The Tamron 18-250 exhibited
mild pincushion distortion at focal lengths from 100mm to
250mm. Vignetting was eliminated by stopping down to f8 at 100mm and
by stopping down to f11 at 250mm.
Handholding a lens at 250mm with an APS-C DSLR requires a shutter
speed of 1/400s or shorter to freeze camera shake. With a maximum
aperture of f6.3, that means bright light or a high ISO setting will
be required. When used with a body with internal image stabilization,
such as the Sony A100 or Pentax K10D, it will be easier to use at
longer focal lengths, but keep in mind that in-body image
stabilization is less effective at longer focal lengths.
Note that distortion and vignetting can be corrected
with digital post-processing.
The Tamron 18-250 focuses down to 0.45m at all focal lengths and gives
a maximum magnification of 0.28x. There is a significant change in
focal length as the lens is close-focused at the 250mm
setting. Despite the fact that the ring on the lens is set to 250mm,
the actual focal length is about 125mm, a common side effect when
using internal focus lenses. The consequence of this is that you get
less magnification that you would otherwise expect when using the
Tamron lens at close range compared with using the Canon EF
70-300/4-5.6IS at the same distance and focal length.
If you want just one lens with an extreme range of focal lengths, the
Tamron 18-250 is one of the most capable options. Center sharpness is
quite good, but you will have to accept low edge sharpness at
telephoto settings. If you value convenience over image quality, the
Tamron 18-250 could be a good choice.
Where to Buy
The Tamron 18-250/3.5-6.3 comes in a variety of lens mounts: