Tamron 17-70mm f/2.8 Di III-A VC RXD Lens for Sony E APS-C Mirrorless Cameras vs Tamron 70-300mm F/4.5-6.3 Di III RXD for Sony Mirrorless Full Frame/APS-C E-Moun

Price and Value

The Tamron 17-70mm f/2.8 Di III-A VC RXD Lens for Sony E APS-C Mirrorless Cameras is priced at C$949.00, whilst the Tamron 70-300mm F/4.5-6.3 Di III RXD for Sony Mirrorless Full Frame/APS-C E-Mount costs C$549.00. The 17-70mm commands a premium of C$400.00, reflecting its significantly wider aperture and broader focal range coverage. For budget-conscious photographers, the 70-300mm offers compelling value as a specialised telephoto solution. However, the 17-70mm has demonstrated stronger market performance with a bestseller rank of 2 compared to the 70-300mm's rank of 13, suggesting it holds greater appeal to Sony mirrorless users seeking versatility in their kit.

Focal Length Range and Coverage

The 17-70mm delivers a 4.1x zoom ratio covering focal lengths from 17-70mm, equivalent to 25.5-105mm on full-frame bodies. This makes it an excellent everyday standard zoom ideal for general photography, travel, and video work. In contrast, the 70-300mm serves as a dedicated telephoto lens with a 4.3x zoom ratio, providing reach from 70-300mm (105-450mm equivalent on APS-C). The 17-70mm covers wide-angle to short telephoto, whilst the 70-300mm focuses purely on telephoto magnification. Photographers must decide whether they need a versatile all-purpose zoom or a specialised tool for distant subjects like wildlife and sports.

Aperture Performance

A defining difference lies in aperture capabilities. The 17-70mm maintains a constant f/2.8 maximum aperture throughout its entire zoom range—a significant achievement that provides consistent light-gathering ability and shallow depth-of-field potential at any focal length. This permits confident handheld shooting in varied lighting conditions and yields superior background separation for creative photography. The 70-300mm, conversely, features a variable aperture of f/4.5 at 70mm closing to f/6.3 at 300mm. This narrower aperture requires faster shutter speeds or higher ISO in low light, particularly at the telephoto end, potentially impacting image stabilisation effectiveness during video work or action photography.

Optical Construction

The 17-70mm incorporates 16 lens elements across 12 groups, including two GM (Glass Molded Aspherical) elements and one hybrid aspherical element. This sophisticated design enables exceptional optical performance with precise aberration correction across the zoom range. The 70-300mm employs 15 elements in 10 groups, similarly optimised for resolving power and chromatic aberration correction—critical for telephoto lenses where such distortions become pronounced. Both lenses employ premium lens technologies appropriate to their focal ranges, though the 17-70mm's additional optical complexity reflects its constant wide aperture requirement and broader zoom ratio, whilst the 70-300mm's design prioritises telephoto specialisation and lightweight portability.

Autofocus and Stabilisation

Both lenses feature Tamron's RXD (Rapid eXtra-silent stepping Drive) autofocus system, providing fast, quiet, and precise focusing. The 17-70mm distinguishes itself with an upgraded VC (Vibration Compensation) mechanism that leverages AI technology when shooting video, enhancing stabilisation beyond conventional models and proving invaluable for videographers. The 70-300mm lacks the enhanced VC system, offering standard stabilisation suitable for photography but potentially limiting smooth video work. For Sony mirrorless enthusiasts, both lenses integrate fully with Fast Hybrid AF and Eye AF features. The 17-70mm's AI-aware stabilisation represents a modern enhancement particularly valuable for contemporary content creators.

Minimum Focusing Distance and Portability

The 17-70mm permits remarkably close focusing, with a minimum object distance of 7.5 inches at 17mm and 15.4 inches at 70mm, enabling macro-like work and detailed photography. The 70-300mm offers up-close shooting at 31.5 inches wide and 59.1 inches tele, with a maximum magnification ratio of 1:9.4 wide and 1:5.1 tele. The 70-300mm compensates through exceptional lightness, weighing just 19.2 ounces and measuring 5.8 inches long—making it supremely portable for outdoor adventure and travel. The 17-70mm, whilst not heavy, sacrifices ultimate portability for versatility. Photographers prioritising handheld mobility and extended shooting sessions will appreciate the 70-300mm's featherweight design.

Construction and Durability

Both lenses feature Moisture-Resistant Construction, providing protection against environmental elements during outdoor shooting. The 17-70mm adds a Fluorine Coating, a premium feature that reduces water and oil accumulation on the lens surface, simplifying maintenance and extending optical clarity in challenging conditions. It accepts Ø67mm filters, matching other Tamron full-frame mirrorless lenses. The 70-300mm's moisture resistance alone provides adequate weather protection for general use without the additional fluorine benefit. The 17-70mm's enhanced coating and filter compatibility suggest a design philosophy emphasising professional-grade durability and maintenance convenience, whilst the 70-300mm prioritises essential protection alongside maximum weight reduction.

Which should you buy?

Choose the Tamron 17-70mm f/2.8 Di III-A VC RXD if you want a single versatile lens covering everyday photography, travel, and video work with consistent f/2.8 brightness, AI-enhanced stabilisation, and close-focusing capability. Its bestseller ranking of 2 reflects strong photographer satisfaction and justifies the C$949.00 investment for serious Sony mirrorless users seeking optical excellence and creative control. Choose the Tamron 70-300mm F/4.5-6.3 Di III RXD if your primary need is dedicated telephoto reach for wildlife, sports, or distant subjects, and you value exceptional portability and lighter carrying load. At C$549.00, it delivers specialised performance at a significant price advantage, ideal for photographers with more focused telephoto needs or those budgeting for complementary lenses. The 17-70mm is the more capable all-rounder; the 70-300mm is the specialist's choice.