Sony FE 100-400mm f/5.6-8 OSS vs Tamron 70-300mm f/4.5-6.3 Di III RXD

Both are Sony E mount zooms for telephoto and wildlife — here's how the specs differ and which to pick. Every spec is from the manufacturer's own catalog.

Last verified 2026-09-01 · Sony E mount · prices change — check the retailer

Spec	Sony FE 100-400mm f/5.6-8 OSS	Tamron 70-300mm f/4.5-6.3 Di III RXD
Focal length	100-400mm	70-300mm
Max aperture	f/5.6-8	f/4.5-6.3
Type	zoom	zoom
Coverage	full-frame	full-frame
Mount	Sony E	Sony E

Which should you buy?

the Tamron 70-300mm f/4.5-6.3 Di III RXD opens wider (f/4.5-6.3) — brighter in low light and more background blur
the Sony FE 100-400mm f/5.6-8 OSS covers 100-400mm and the Tamron 70-300mm f/4.5-6.3 Di III RXD covers 70-300mm — pick the range that matches what you shoot
the Sony FE 100-400mm f/5.6-8 OSS is first-party (Sony) for guaranteed full autofocus and in-camera corrections; the Tamron 70-300mm f/4.5-6.3 Di III RXD is third-party — usually the value pick

Where to buy

Sony FE 100-400mm f/5.6-8 OSSSee price on Amazon

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Tamron A047SF - Telephoto Lens - 70-300mm F/4.5-6.3 Di III RXD for Sony FE, Black

Tamron 70-300mm f/4.5-6.3 Di III RXDSee price on Amazon

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FAQ

What's the difference between the Sony FE 100-400mm f/5.6-8 OSS and the Tamron 70-300mm f/4.5-6.3 Di III RXD?
The Sony FE 100-400mm f/5.6-8 OSS is 100-400mm f/5.6-8 zoom, full-frame; the Tamron 70-300mm f/4.5-6.3 Di III RXD is 70-300mm f/4.5-6.3 zoom, full-frame. Both fit the Sony E mount.

Which is better in low light, the Sony FE 100-400mm f/5.6-8 OSS or the Tamron 70-300mm f/4.5-6.3 Di III RXD?
The Tamron 70-300mm f/4.5-6.3 Di III RXD — its f/4.5-6.3 maximum aperture lets in more light and gives more background blur than the f/5.6-8 of the other.

Do the Sony FE 100-400mm f/5.6-8 OSS and Tamron 70-300mm f/4.5-6.3 Di III RXD fit the same camera?
Yes — both are Sony E mount lenses, so they fit Sony a7/a9/a1 (full-frame) and a6000-series (APS-C).

Citing these specs? Go ahead — manufacturer data, last verified 2026-09-01. Copy a ready-made reference:

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Sony FE 100-400mm f/5.6-8 OSSAffiliate linkSee price on Amazon