Sigma 100-400mm f/5-6.3 DG DN OS Contemporary Lens (Fuji X)

The Sigma 100‑400mm f/5‑6.3 DG DN OS Contemporary is an ultra‑telephoto zoom lens built to deliver long‑reach performance in a relatively compact, lightweight package for mirrorless cameras with the Fuji X mount. It’s part of Sigma’s Contemporary line, which focuses on balancing optical quality, manageable size, and everyday usability.

Key Specifications and Features

• Focal Length: 100–400 mm. On Fujifilm APS‑C bodies this effectively covers roughly 150–600 mm equivalent focal length in full‑frame terms, making it excellent for distant subjects like wildlife and sports.
• Maximum Aperture: Variable f/5 at 100 mm to f/6.3 at 400 mm — common for long telephoto zooms to keep the size and weight reasonable while still usable in good light.
• Minimum Aperture: f/22–29 depending on zoom position.
• Lens Construction: 22 optical elements in 16 groups, including one FLD and four SLD elements to reduce chromatic aberration and maintain good sharpness across the zoom range.
• Autofocus System: Fast, quiet stepping motor (STM) for autofocus that works well for both stills and video; internal focusing maintains the lens length during focus changes.
• Optical Stabilization: Built‑in OS (Optical Stabilizer) rated for up to around four stops of shake reduction that helps with handheld shooting at long focal lengths.
• Minimum Focusing Distance: About 1.12 m (wide end) to 1.60 m (telephoto), with a maximum magnification of about 1:4.1 at 400 mm for close‑up detail on distant subjects.
• Diaphragm: Rounded 9‑blade diaphragm for smoother background blur (bokeh).
• Filter Size: φ67 mm – same thread as many other Sigma Contemporary lenses, which helps if you already own matching filters.
• Physical Size & Weight: Approximately 86 mm diameter × 199.5 mm length, with weight around 1,135 g (protective cover included).
• Mount Build: Dust‑ and splash‑resistant mount sealing for better reliability in varied outdoor conditions.
• Supplied Accessories: Lens hood (LH770‑05), protective cover (PT‑31), front cap, and rear cap included.

Optical and Handling Characteristics
This lens’s optical design maintains good image quality across its zoom range, with special glass elements controlling chromatic aberrations and delivering strong contrast and clarity. The optical stabilizer helps a lot when shooting handheld at long focal lengths where camera shake is most noticeable. Focus and zoom rings are smooth, and the lens is designed for comfortable handling despite its telephoto reach.

Practical Applications
The 100–400mm range makes this lens ideal for:

• Wildlife photography (birds, animals at a distance)
• Sports and action shooting
• Outdoor events and nature photography
• Occasional portrait compression at longer focal lengths

Pros

• Excellent reach with manageable size and weight for a telephoto zoom.
• Effective image stabilization for handheld shots.
• Quiet and responsive autofocus.
• Sharp image quality throughout most of the zoom range.
• Weather‑resistant mount construction.

Cons / Considerations

• Relatively slow maximum aperture (f/5‑6.3) means it performs best in good light; low‑light shooting may require higher ISO.
• Long focal lengths on APS‑C bodies demand steady technique or stabilization for best results.