The Sigma 100-400mm f/5-6.3 delivers impressive optical performance across its zoom range.

Sharpness

• Center Sharpness:
  • Excellent sharpness in the center at all focal lengths, particularly at 100-300mm.
  • Slight softness at 400mm wide open, which improves when stopped down to f/8.
• Edge Sharpness:
  • Edge performance is strong at shorter focal lengths but falls off slightly at 400mm, though still respectable for this price range.
• Consistency:
  • Sharpness is consistent across the zoom range, making it suitable for various types of photography, from wildlife to landscapes.

Color Rendering and Contrast

• Color Accuracy: Natural and vibrant colors, maintaining pleasing tones in outdoor and wildlife shots.
• Contrast: Excellent contrast, even in backlit conditions, thanks to advanced lens coatings.

Bokeh

• Background Blur:
  • Despite its slower aperture, the long focal lengths allow for significant subject isolation.
  • The bokeh is smooth and pleasing, with minimal distracting elements.
• Highlight Rendering:
  • Round and soft highlights, though not as creamy as premium telephoto lenses.

Optical Aberrations

• Chromatic Aberration:
  • Well-controlled lateral chromatic aberration, with only minor fringing in high-contrast areas.
• Distortion:
  • Negligible barrel or pincushion distortion, which is easily correctable in-camera or during post-processing.
• Flare and Ghosting:
  • Performs well when shooting into direct light, with minimal ghosting or flare due to Sigma’s Super Multi-Layer Coating.
• Vignetting:
  • Noticeable at the wider end of the aperture, especially at 400mm, but easily corrected in post-processing.