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Tamron SP 28-135mm F/4.0-4.5 Model 28A: A wide angle to
moderate telephoto zoom lens which offers above average optical performance.
This lens features an extraordinarily complex mechanical design since all lens
elements move as four separate groups at different rates when zooming. Tamron
accomplished this mechanical engineering feat by using a system of nested
sleeves controlled by a series of five cam-slots and cam-followers. A separate
solid brass focusing helicoid moves the entire lens forward during the "macro"
focusing action. This feature is engaged by pressing a small button on one of
the two "macro" ring grips and then rotating the macro ring. Maximum macro
magnification ratio is 1:4 at the 28mm zoom position.
Overall, this is an extremely versatile lens since it is sharp,
has a decently fast maximum aperture and covers everything from wide angle to
medium telephoto. Tamron rightly chose to optimize the optical performance of
this lens for the wide angle to slight telephoto settings since these focal
lengths are the most frequently used in everyday shooting situations. Optical
performance is above average within the 28 to 80mm zoom range. Off-axis
performance drops off to average between the 80 to 135mm settings. On-axis
performance is very good throughout — even in macro mode. Macro
performance is decent for the central 50% of the field of view but then rapidly
falls off towards the corners. Keep in mind that the macro mode was built into
this lens as an additional sales feature. Nevertheless the macro is quite
usable in a pinch, especially if your macro subject is centered and occupies no
more than about one half of the field of view.
Lens Specifications:
| Lens Model |
28A |
| Focal Length |
28 — 135mm |
| Aperture Range |
f/4~4.5 — 32, AE |
| Angle of View |
75°~18° |
Optical
Construction
(Groups / Elements) |
10 / 17 |
Min. Focus from Film
Plane
(normal mode) |
78.7" (2.0m)
|
Min. Focus from Film
Plane
(macro mode) |
51.2" (1.3m) at
f=135mm
10.2" (0.26m) at f=28mm |
| Macro Mag.
Ratio |
1:1:4 at f=28mm |
| Filter Size |
67mm |
| Diameter |
2.8" (70mm) |
Length at
[w/Nikon mount] |
4.2" (106mm)
[4.4" (110.5mm)] |
| Weight |
25 oz. (710g) |
| Lens Hood |
Bayonet type #45FH (optional extra). |
| Accessory |
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