Build Quality & Features – Both lenses have similar construction, made of tough plastic. From a distance, you might mistake the Sigma for metal, but it’s the same basic material as the Tamron. Both feel well made, feature telescoping zoom, and have internal focusing—great for using circular polarizers.
• Filter Size: Tamron uses 67mm; Sigma uses 72mm.
• Lens Hood: Both include one.
One downside of the Tamron is its small and slippery AF/MF and IS (VC) switches. Sigma’s switches are slightly taller and easier to operate. However, the Tamron offers full-time manual focus, a great feature that allows quick fine-tuning. On a lens with this much range, focusing can be slow, and the ability to assist AF or manually fine-tune focus makes for a much smoother experience.
The Tamron’s stabilization also seems slightly better—noticeable in slower shutter speed handholding and when shooting video, where it appears just a bit smoother.
Weight – Sigma: 1lb 5oz, Tamron: 1lb 4oz.
Focusing Speed – Both use ultrasonic focusing systems (HSM for Sigma, PZD for Tamron). I tested them at Longwood Gardens using a Canon 7D Mark II on a moving train display. In both One Shot and AI Servo modes, the Tamron consistently kept focus on trains moving directly toward me. With the Sigma, some shots were slightly out of focus—it was just a bit slower. The Tamron also performed slightly smoother in video focusing.
Macro Capabilities – Identical for both lenses.
• Close Focus Distance: 15” with AF, ~6” with MF.
• Magnification: Same for both.
• Sigma’s 2x Magnification Filter: A $50 screw-on filter designed to double magnification.
Image Quality
• Sharpness: The Sigma is slightly sharper, and when viewing at 100% or more, the difference is noticeable.
• Chromatic Aberration: The Sigma shows significantly more purple/magenta fringing, which may be due to its increased sharpness.