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Tamron 70-300mm F/4.5-6.3 Di III RXD vs Sigma 18-50mm f/2.8 DC DN Contemporary

These are not substitutes: the Tamron is a full-frame 70-300mm telephoto zoom, and the Sigma is an APS-C 18-50mm f/2.8 standard zoom. Buy the Tamron if you need reach for sports, wildlife or outdoor action. Buy the Sigma if you want a bright, small everyday zoom for an APS-C Sony body. On price, the Tamron is $349.00 at Walmart as of November 6, 2026, while the Sigma has ranged from $389.99 on November 4, 2026 to $499.00 on November 3, 2026.

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Tamron
Tamron 70-300mm F/4.5-6.3 Di III RXD Lens A047 for Sony E-mount Full Frame Mirrorless

Tamron 70-300mm F/4.5-6.3 Di III RXD

Tamron 70-300mm F/4.5-6.3 Di III RXD Lens A047 for Sony E-mount Full Frame Mirrorless

4.7(13 ratings)
$369.00at Amazon
Observed at 5:24 AM
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Choose the Tamron 70-300mm if you shoot full-frame Sony E-mount and need long reach in a light, low-cost package.

Pros
  • Cheapest way to reach 300mm on full-frame Sony E-mount
  • Light for a full-frame telephoto at 545 g
  • Quiet RXD stepping autofocus motor
  • 67mm filter thread, common size
Cons
  • Slow f/6.3 at 300mm limits low-light and action shooting
  • 1.5m minimum focus at tele is far
  • No optical stabilization; relies on body IBIS
  • No weather sealing listed
Sigma
Sigma 18-50mm f/2.8 DC DN Contemporary

Sigma 18-50mm f/2.8 DC DN Contemporary

4.9(692 ratings)

Choose the Sigma 18-50mm f/2.8 if you shoot an APS-C Sony body and want a fast, compact walk-around zoom.

Pros
  • Constant f/2.8 across the zoom range
  • Very small and light at 290 g and 74.5mm long
  • Close focus of 12.1 cm with 1:2.8 magnification
  • Weather-sealed, with internal focusing
Cons
  • APS-C only; no full-frame coverage
  • No optical stabilization
  • 50mm long end is short for portraits or reach
  • Priced above the Tamron at recent lows

What separates them

Tamron 70-300mm F/4.5-6.3 Di III RXDSigma 18-50mm f/2.8 DC DN Contemporary
Sensor formatFull-frame, also works on APS-CAPS-C only (27-75mm equivalent)
Focal range70-300mm telephoto18-50mm standard zoom
Maximum aperturef/4.5-6.3Constant f/2.8
Weight545 g (19.2 oz)290 g
Length148mm (5.8 in)74.5mm
Minimum focus distance0.8m wide / 1.5m tele12.1 cm
Maximum magnification1:5.1 at tele1:2.8 at 18mm
Weather sealingNot specifiedWeather-sealed

Price history

$499.00$369.00
Nov 3Nov 6
  • Tamron 70-300mm F/4.5-6.3 Di III RXD: lowest $369.00 on Nov 6 at Amazon.
  • Sigma 18-50mm f/2.8 DC DN Contemporary: lowest $389.99 on Nov 4 at Cardinal Camera.

Prices at every store

Tamron 70-300mm F/4.5-6.3 Di III RXD

  • Teds ElectronicsNew

    In stock

    $389.99Free shippingObserved at 5:24 AM
    Visit store
  • eBayNew

    In stockSold by nyjbloom

    $444.31+ $143.00 shippingObserved at 5:24 AM
    Visit store
  • AmazonNew

    Availability unknown

    As an Amazon Associate, Deal.ai earns from qualifying purchases.

    $369.00Free shippingObserved at 5:24 AM
    Visit store

Also available at

  • eBayCheck price at eBay
  • WalmartCheck price at Walmart
All 3 stores and price history →

Sigma 18-50mm f/2.8 DC DN Contemporary

  • Rockbrook CameraCheck price at Rockbrook Camera
  • WalmartCheck price at Walmart
  • AmazonCheck price at Amazon
Prices and history →

Specs compared

SpecTamron 70-300mm F/4.5-6.3 Di III RXDSigma 18-50mm f/2.8 DC DN Contemporary
colorBlackBlack
Length148mm / 5.8 in (Sony)74.5 mm
Weight545g / 19.2 oz (Sony)290 g
Aperture blades7 (circular diaphragm)7
Minimum apertureF22-32f/22
Angle of view34゜21'-8゜15'—
Optical construction15 elements in 10 groups—
Minimum object distance0.8m (31.5 in) (WIDE) / 1.5m (59.1 in) (TELE)—
Maximum magnification1:9.4 (WIDE) / 1:5.1 (TELE)—
Filter sizeΦ67mm—
Maximum diameterΦ77mm—
size—4.8" / 12.1 cm
Show all 40 specsShow fewer specs
SpecTamron 70-300mm F/4.5-6.3 Di III RXDSigma 18-50mm f/2.8 DC DN Contemporary
Mount—Sony E
Maximum Aperture—f/2.8
Aspherical—Yes
Type—Zoom
Zoom Focal Length—18-50mm
Durability—Weather-sealed
Magnification—1:2.8 (at 18mm)
Accessory Type—Lens
Hood Type—Petal hood
Lens Type—

What reviewers say

Tamron 70-300mm F/4.5-6.3 Di III RXD

  • 4.7 / 513 ratings

Owners rate it highly, at 4.7 out of 5 from 13 ratings, and most praise its low weight and image quality for the money. Complaints center on the dim f/6.3 aperture and the plasticky feel.

What people mention
  • WeightPraisedOwners say it is easy to carry and shoot handheld for long stretches.
  • SharpnessPraisedReviewers find it sharp for the price, especially stopped down slightly.
  • ApertureCriticisedThe f/6.3 maximum at 300mm makes it hard to use in dim light or for fast action.
  • BuildCriticisedBuyers describe the barrel as plastic and not weather sealed.

Sigma 18-50mm f/2.8 DC DN Contemporary

  • 4.9 / 5692 ratings

Owners rate it very highly, at 4.9 out of 5 from 692 ratings. Most praise the size-to-aperture ratio and sharpness, and accept the plastic build and lack of stabilization as the price of that compactness.

Pros
  • Small and light enough to carry all day
  • f/2.8 at every focal length
  • Sharp images, especially in the center
  • Good value against first-party f/2.8 zooms
Cons
  • No optical stabilization
  • Barrel is plastic and not weather sealed
  • No lens hood included
  • Corner softness wide open

Questions and answers

Which is better for wildlife?
The Tamron. Its 300mm reach on full-frame is far longer than the Sigma's 75mm equivalent, though f/6.3 at the long end needs good light.
Which is better for travel and everyday shooting?
The Sigma. It weighs 290 g, is 74.5mm long and holds f/2.8, which suits indoor, street and low-light shooting.
Can I use the Sigma on a full-frame Sony body?
Only in APS-C crop mode, which cuts resolution. The Tamron covers full-frame and also works on APS-C bodies.
Is the Sigma worth the extra money?
If you shoot APS-C and want f/2.8 in a pocketable zoom, yes. If you need reach, the Tamron at $349.00 at Walmart as of November 6, 2026 is the cheaper buy.
Which focuses closer?
The Sigma, at 12.1 cm with 1:2.8 magnification. The Tamron's minimum focus is 0.8m at wide and 1.5m at tele.
Do either have image stabilization?
Neither lens has optical stabilization. Both rely on the camera body's IBIS, which helps most on the Sigma's shorter focal lengths.

More comparisons

  • Sigma 18-50mm f/2.8 DC DN Contemporary vs Sony FE 24-70mm f/2.8 GM II
  • Sigma 18-50mm f/2.8 DC DN Contemporary vs Tamron 70-180mm f/2.8 Di III VC VXD G2 Lens
  • Sigma 16-300mm F3.5-6.7 DC OS Contemporary Lens For Sony E-Mount vs Sigma 18-50mm f/2.8 DC DN Contemporary
  • Sigma 18-50mm F2.8 DC DN Contemporary Lens For Sony E-Mount vs Tamron 70-300mm F/4.5-6.3 Di III RXD Lens A047 for Sony E-mount Full Frame Mirrorless
  • Sigma 10-18mm F2.8 DC DN Contemporary Lens For Sony E-Mount vs Sigma 18-50mm f/2.8 DC DN Contemporary

Buying guides that pick them

  • Best Sigma zoom lenses for Sony E-mount under $500
  • Best Sony E-mount lenses
Zoom lens
Aperture Range—f/2.8
Teleconv &Amp; Add-On Lenses—Extension tube
Specialty Type—Macro, Portrait
Elements—13
Focus Adjustment—Autofocus
Minimum Focus Distance—12.1 cm
Focus Highlights—Internal Focusing System
Included Accessories—Lens hood
Included Highlights—With Lens Hood
Diameter—61.6 mm
Image Stabilization—No
Lens Mount Compatibility—Sony E-Mount, Sony E-Mount, Sony E-Mount, Sony …
Minimum Focal Length—18 millimeters
Maximum Focal Length—50 millimeters
Brand—Sigma
Model Number—585965
Compatible Devices—Mirrorless Camera
Brand Compatibility—Sony, Sony, Sony, Sony, Sony