Designed for digital SLRs with APS-sized sensors in mind, Tamron has created this lens which boasts a fantastic 13.9X zoom range which as of September 2006 was the world's largest range in a camera lens. In 35mm camera terms, the focal length covers the equivalent of 28-388mm.
With its lightweight and compact design it can truly be said that it is a milestone in digital SLR lens technology.
Optical Design
The lens uses a Low Dispersion (LD) element and an Anomalous Dispersion (AD) lens in the first group to minimise on-axis chromatic aberration. There are also two hybrid aspherical elements suitably positioned to afford sharp image performance at the same time as being compact. Indeed the whole configuration has been carefully analysed by the engineers at Tamron to ensure optimum power distribution in the overall optical system and effective correction of all aberrations including for example astigmatism.
Another important consideration especially with digital zoom lenses is the need to restrict the varying angles of incident light falling on the image sensor (and limit any resultant internal reflections). Again this has been factored into the design of this lens to minimise such effects. In addition, the use of "internal surface coatings" (ie even on cemented lens surfaces) further reduces internal reflections within both the lens and the camera sensor.
A
Constant minimum focus distance of 45cm (17.7") is achieved giving great closeup shots at any focal length. If used at the 250mm focal length a magnification ratio of 1:3.5 can be achieved.
Zoom Lock
Prevents unwanted barrel extension ("tromboning") during use and when carried on the camera.
(Petal Hood included as standard)
Specifications
- Focal Length: 18-250mm
- Maximum Aperture: f3.5-6.3
- Angle of View: 75 deg 33 m- 6 deg 23m (on APS-C sensor)
- Lens Construction: 16 elements in 13 groups
- Min Focus distance: 0.45m (17.7") over entire zoom range
- Max magnification Ratio: 1:3.5 at f=250mm
- Overall Length: 84.3mm
- Maximum Diameter: 74.4mm
- Weight: 430g
- Diaphragm Blades: 7
- Minimum Aperture: f22