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Canon RF 100-400mm f/5.6-8 — Prime/Zoom
Canon

Canon RF 100-400mm f/5.6-8

Prime/Zoom

84
/ 100
From $649
VS
Tamron 20-40mm f/2.8 Di III VXD wins by 1
Tamron 20-40mm f/2.8 Di III VXD — Prime/zoom
Tamron

Tamron 20-40mm f/2.8 Di III VXD

Prime/zoom

85
/ 100
From $699
Specdex verdict

Tamron 20-40mm f/2.8 Di III VXD takes it — here’s why.

In our weighted Specdex score, Canon RF 100-400mm f/5.6-8 lands at 84 and Tamron 20-40mm f/2.8 Di III VXD at 85. That puts Tamron 20-40mm f/2.8 Di III VXD ahead by 1 points — a narrow margin driven mostly by its strengths in the categories below.

Pick Canon RF 100-400mm f/5.6-8 if…

  • ✓Fast aperture
  • ✓Quiet autofocus
  • ✓Weather-sealed (most)

Pick Tamron 20-40mm f/2.8 Di III VXD if…

  • ✓Proven optical formula
  • ✓Weather-sealing (L/GM/S)
  • ✓Strong resale
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Winner by scenario

Derived from the sub-score breakdown · not a separate test

Build

Tamron 20-40mm f/2.8 Di III VXD

Compared on the build sub-score

Tamron 20-40mm f/2.8 Di III VXD leads on build (90 vs 88).

Sharpness

Tie

Compared on the sharpness sub-score

Effectively tied — neither pulls a 2-point weighted lead.

Autofocus

Tie

Compared on the autofocus sub-score

Effectively tied — neither pulls a 2-point weighted lead.

Value for money

Tie

Specdex score per dollar at MSRP

Effectively tied — similar score-per-dollar at MSRP.

Canon RF 100-400mm f/5.6-8 84
vs
85 Tamron 20-40mm f/2.8 Di III VXD

Score breakdown

Canon RF 100-400mm f/5.6-8
84
sharpness 84
af 82
build 88
value 85
Tamron 20-40mm f/2.8 Di III VXD
85
sharpness 85
af 81
build 90
value 86

Specs side-by-side

Canon RF 100-400mm f/5.6-8 versus Tamron 20-40mm f/2.8 Di III VXD — full spec comparison
Spec Canon RF 100-400mm f/5.6-8 Tamron 20-40mm f/2.8 Di III VXD

Canon RF 100-400mm f/5.6-8

Pros
  • +Fast aperture
  • +Quiet autofocus
  • +Weather-sealed (most)
Cons
  • −Mount-specific
  • −Weight varies
  • −Price scales with quality

Tamron 20-40mm f/2.8 Di III VXD

Pros
  • +Proven optical formula
  • +Weather-sealing (L/GM/S)
  • +Strong resale
Cons
  • −Mount-specific
  • −Older AF motor on some
  • −Heavier than modern counterparts

FAQ: Canon RF 100-400mm f/5.6-8 vs Tamron 20-40mm f/2.8 Di III VXD

Which is better, Canon RF 100-400mm f/5.6-8 or Tamron 20-40mm f/2.8 Di III VXD? +

Tamron 20-40mm f/2.8 Di III VXD scores 85 on our weighted rubric — ahead by 1. Your best pick depends on the sub-scores above.

Is Canon RF 100-400mm f/5.6-8 worth the price? +

At $649, Canon RF 100-400mm f/5.6-8 delivers a Specdex score of 84 — strongest in build.

Is Tamron 20-40mm f/2.8 Di III VXD worth the price? +

At $699, Tamron 20-40mm f/2.8 Di III VXD delivers a Specdex score of 85 — strongest in build.

Does Canon RF 100-400mm f/5.6-8 or Tamron 20-40mm f/2.8 Di III VXD last longer? +

Based on our long-term update and support ratings, both ship with multi-year support. Battery and reliability scores are visible in the breakdown above.

Which is better for build, Canon RF 100-400mm f/5.6-8 or Tamron 20-40mm f/2.8 Di III VXD? +

Tamron 20-40mm f/2.8 Di III VXD — leads on build (90 vs 88). Compared on the build sub-score.