Tamron's basic Adaptall-2 telephoto — the 70-210mm f/3.8 without SP tier.
The Tamron 70-210mm f/3.8 in Adaptall-2 is a basic telephoto zoom without the SP designation. The constant f/3.8 provides consistent exposure — a modest advantage. The 70-210mm covers standard telephoto. The Adaptall-2 cross-system mount is the main feature. Below SP quality but the constant aperture adds some value.
Basic Tamron quality — below SP tier. The constant f/3.8 provides consistent exposure — an advantage over variable alternatives. Sharpness acceptable. The 70-210mm is standard telephoto. Build quality functional. The SP version (IDs 4599, 4600) is preferred for quality. The constant aperture is this lens's advantage.
Adaptall-2 universal mount. Filter thread varies. Weight varies. Constant f/3.8. Below SP quality. Ensure correct adapter. The SP versions are preferred. The constant aperture distinguishes this from variable-aperture Tamron alternatives at the non-SP level.
Very cheap. Constant f/3.8 is a modest advantage. SP versions preferred. Ensure adapter. A basic telephoto with the Adaptall-2 versatility. Only at near-zero prices when SP versions are unavailable.