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Tamron Adaptall-2 70-150mm F/3.5 Model 20A: Introduced in
1980, this lens is a completely new optical and mechanical design compared to
the model 02A introduced the previous year. This lens is considerably lighter
and is a full 1" shorter than its predecessor. Optical performance is somewhat
better than average compared to similar lenses of the era, particularly towards
the corners in the 100 to 150mm zoom range. This lens is extremely compact,
features a one-touch focus/zoom collar compared to the separate two-touch focus
and zoom collars of the previous year's design, features continuous focusing
(CF) into macro mode, and features a built-in retractable lens hood. Overall,
this lens is one of the better performing and handling lenses within its
class.
It should be noted that this lens really has a maximum aperture of
F/4, something which Modern Photography noted in their test reports by
specifying the 5% aperture tolerance based on F/4. This the only example of
which we are aware of where Tamron deliberately mis-labeled the maximum
aperture. Why? Obviously for marketing reasons since the similar Tokina lens
was a strong competitor which also offered nearly equal optical performance.
Modern should have explicitly mentioned the true F/4 maximum aperture in their
test report. They didn't, most likely since Tamron was a consistent advertiser
in their magazine.
Lens Specifications:
| Lens Model |
20A |
| Focal Length |
70 — 150mm |
| Aperture Range |
f/3.5 — 32, AE |
| Angle of View |
34°~16° |
Optical
Construction
(Groups / Elements) |
10 / 13 |
| Min. Focus from Film
Plane |
27.5" (0.7m) |
| Macro Mag. Ratio [w/2X
Converter] |
1:3 [1:1:5] |
| Filter Size |
49mm |
| Diameter |
2.5" (64.5mm) |
Length at
[w/Nikon mount] |
3.9" (99mm)
[4.1" (103.5mm)] |
| Weight |
16.2 oz. (459g) |
| Lens Hood |
Built-in type, retractable. |
| Accessory |
Accepts SP 2X tele-converter #01F. |
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