Model 31A
SP Symbol200~500mmF/5.6
Ultra-Tele Zoom
Tamron SP Adaptall-2 200-500mm F/5.6 Model 31A Lens

Tamron SP 200-500mm F/5.6 Model 31A: The introduction of this lens in 1984 coincided with the discontinuation of Tamron's somewhat less than spectacular 200-500 F/6.9 model 06A Adaptall-2 lens. Tamron's optical engineers decided to start fresh by creating a completely new optical design for the model 31A. Design parameters were an adequately fast F/5.6 aperture for easier focusing with split image and microprism viewfinders, superior reduction of chromatic and spherical aberrations, and superior resolution and contrast across a very flat field. Optical performance is significantly above average which makes this lens worthy of Tamron's SP designation. Although this lens is not an APO, its corrections for chromatic and spherical aberrations are similar to a very good conventional 300mm telephoto.

The optical design starts with a conventional three element triplet for the focus group. The zoom group uses four elements for the variator group and three elements for the compensator group. This seven element zoom group design allowed Tamron's optical engineers to tightly control off-axis aberrations. The SP 200-500 is lens is capable of close focusing to 8.2 feet for a 1:3.52 maximum magnification ratio, but the lens will exhibit moderate amounts of spherical aberration at very close focus distances. Close focusing induced spherical aberration is greatly minimized by F/11. Remember to shoot at F/11 to F/16 when photographing subjects which are closer than about 20 feet, and for critical sharpness at close focus distances, carefully focus with the lens stopped down to the F/11 to F/16 shooting aperture since this method compensates for the slight spherical aberration induced focus shift. This method applies to virtually any long telephoto lens when close focusing.

Note that this lens was designed for superior off-axis performance rather than for compactness. A more compact lens would have necessitated the use of expensive low dispersion plus high refractive index elements in order to maintain superior off-axis image quality. Obviously such a design would have greatly increased the price. Thus Tamron achieved its design goal of producing a long telephoto zoom with excellent performance at a price which was significantly less than comparable OEM lenses. Overall, this is an excellent lens for use with older manual focus film SLR cameras.

Lens Specifications:

Lens Model 31A
Focal Length 200 — 500mm
Aperture Range f/5.6 — 32, AE
Angle of View 12°~5°
Optical Construction
(Groups / Elements)
10 / 14
Min. Focus from Film Plane 98.4" (2.5m)
Macro Mag. Ratio 1:3.52
Filter Size 95mm (front), 43mm (rear)
Diameter 4.1" (105mm)
Length at
[w/Nikon mount]
14.2" (360.5mm)
[14.4" (365mm)]
Weight 96.1 oz. (2724)
Lens Hood Built-in type, retractable.
Accessory Accepts SP 2X tele-converter #01F. Supplied with exclusive tripod mount ring and hard carrying case.
Copyright ©2005-MEM-TEK. All rights reserved. Site contents, services and terms of use are subject to change without notice. Adaptall-2.com is not is not affiliated with Tamron Co., Ltd. or with any of its subsidiary companies. Tamron Co., Ltd. and its subsidiaries neither endorse, control, nor claim any responsibility for the content and accuracy of this Web site.