MIRRORLESSLENSWORLD · CURATED COMPARISON

Sigma 18–50mm f/2.8 vs Tamron 17–70mm f/2.8 VC

These lenses share a constant f/2.8 maximum aperture, but they solve different kit problems. The Sigma emphasizes portability; the Tamron offers longer reach and lens-based stabilization.

Sony a6400 · E mountManufacturer specsUsed market contextKeep / buy comparison

In this comparisonKey specifications Used market Trade-offs Decision guide

Key specifications that actually change the decision

OPTION 1

Sigma 18-50mm f/2.8 DC DN C (Contemporary) Autofocus APS-C Lens for Sony E-Mount

Actual focal range: 18–50mm
Maximum aperture: 2.8
Lens weight: 290 g
Optical stabilization: Not present
Focus drive: Stepping-motor autofocus
Model code: Sigma C021 Sony E

Source: Sigma 18–50mm F2.8 DC DN specifications

Constant f/2.8 APS-C standard zoom. On the a6400 it offers better aperture flexibility than a slow kit zoom, but focal range overlaps the 16–50mm. No optical stabilization; do not mistake wider aperture for a stabilized image.

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OPTION 2

Tamron 17-70mm f/2.8 Di III-A VC RXD APS-C Lens for Sony E-Mount

Actual focal range: 17–70mm
Maximum aperture: 2.8
Lens weight: 525 g
Optical stabilization: Present
Focus drive: RXD autofocus
Model code: Tamron B070 Sony E

Source: Tamron 17–70mm B070 specifications

Constant f/2.8, VC stabilization and 17–70mm APS-C range; a heavier, longer alternative to a compact kit zoom. Manufacturer confirms the 525g Sony version, distinct from other mount weights.

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Used-market evidence, not an invented deal score

Sigma 18-50mm f/2.8 DC DN C (Contemporary) Autofocus APS-C Lens for Sony E-Mount

$617–$655

5 recently observed KEH condition listings · Excellent, Excellent Plus, Like New Minus

In 41 recorded daily observations, the median daily minimum was $617 (observed range $451–$629).

Tamron 17-70mm f/2.8 Di III-A VC RXD APS-C Lens for Sony E-Mount

$543–$575

3 recently observed KEH condition listings · Excellent, Excellent Plus, Like New Minus

In 41 recorded daily observations, the median daily minimum was $629 (observed range $524–$639).

Historical minimum prices may refer to different used copies and different condition grades. The current advertised price can change. These figures are context—not a claim that today's cheapest copy is the best value.

Important differences before you buy

Aperture is not the only low-light decision

Both offer f/2.8 throughout the zoom range. Neither freezes a moving child simply because it has stabilization. The Tamron's VC can help reduce camera shake in static scenes; the Sigma lacks optical stabilization and the Sony a6400 has no in-body stabilization.

Travel weight and focal reach

The Sigma is 290 g with an 18–50mm range. The Tamron weighs 525 g and reaches 70mm from a slightly wider 17mm starting point. That 235 g difference is meaningful when carrying a lightweight kit all day.

Why not simply keep the kit zoom?

If the existing 16–50mm lens already meets your needs, its small collapsed size remains a real advantage. A larger f/2.8 zoom only earns its cost if you need the wider usable aperture, additional controls or Tamron's longer reach and stabilization.

Which choice suits your kit?

CHOOSE OPTION 1 IF

Prioritize if travel weight and a compact f/2.8 zoom matter more than reach or in-lens stabilization.

CHOOSE OPTION 2 IF

Prioritize if you want a stabilized constant-aperture zoom, extended 70mm reach, and accept extra bulk.

KEEP YOUR CURRENT LENS IF

Keep your current kit zoom when portability and price matter more than the specific additional capabilities.

These are specification-based buying considerations, not independent optical tests. Confirm each used copy's exact model, optical condition, included accessories and return terms with the retailer.

Run your own Sony a6400 kit assessment →Explore the other curated comparison →