Sigma 40mm f/1.4 Art Lens for SONY Review - Is BIGGER Better?

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Gerald Undone

Gerald Undone

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Sigma 40mm Art Lens

The Sigma 40mm Art Lens has raised the question of whether bigger is better. With its monster-like size, it aims to address the flaws of the popular 35mm lens from Sigma and become the perfect lens in that focal range. In this review, we'll compare it to the 35mm and explore the impressive MTF charts that demonstrate its optical performance.

Understanding MTF Charts

MTF charts, or Modulation Transfer Function charts, play a crucial role in evaluating a lens's optical performance. These charts measure how well a lens handles different spatial frequencies, particularly the sharpness and contrast between lines. The MTF chart for the Sigma 35mm lens shows a high level of performance, maintaining about 40% sharpness at the absolute corner. The lens designation as 'Art Lens' is well-deserved based on these results.

Sigma 40mm: An Affordable Marvel

The Sigma 40mm lens offers exceptional performance at a more affordable price compared to high-end lenses like the ZEISS Otus 55mm f/1.4. Its MTF chart shows outstanding sharpness, with the contrast line approaching perfection and sharpness staying above 90% for a significant portion of the frame. Real-world tests confirm its superiority over a 35mm lens, displaying noticeable gains in sharpness and smoother bokeh. Despite being a longer lens with shallower depth of field, it maintains impressive sharpness even wide open at different apertures.

Price Increase for Sigma 40mm

The Sigma 40mm lens has seen a price increase compared to previous Art lenses, now priced at $1400 US. However, the MTF chart and real-world tests demonstrate that the lens justifies its cost, delivering performance on par with much more expensive lenses like the ZEISS Otus 55mm f/1.4. Its sharpness, low distortion, and reduced vignetting make it a top choice for photographers seeking excellent image quality. The lens performs impressively across the frame, particularly at f/5.6, which is its sharpest aperture, while still maintaining exceptional performance even when used wide open.

Advantages of the 40mm Art Lens

The 40mm Art Lens shows a significant improvement over the 35mm Art Lens, particularly when it comes to sharpness and cropping capability. If you enjoy punching in on your photos, the 40mm lens offers clear advantages, even when compared to other Art lenses. The lens was taken to a wrecking yard to shoot some smashed up cars, demonstrating its sharpness and cropping potential.

Focus Breathing and Autofocus Comparison

The 35mm Art Lens suffers from noticeable focus breathing, as demonstrated in a comparison with the 40mm Art Lens. While the 40mm lens still exhibits some breathing, it shows about a 30-40% improvement over the 35mm, making it a better option. In terms of autofocus, the Art lenses have strong motors that work well with AF Single, but the 35mm is jerky and sluggish in video autofocus. The 40mm lens performs better in continuous burst-fire focusing, resulting in a higher keeper rate, making it suitable for subjects getting closer to the lens.

AF Performance and Close Focusing Range

The 40mm lens shows a small but consistent improvement in AF performance at closer focusing ranges. However, with video, it's challenging to determine if there's a noticeable improvement. When set to 'fast' AF speed on Sigma lenses, the lens performs well, but it remains less responsive up close. At a normal distance, the lens locks on and holds focus without issues. However, when comparing it to the 35mm lens for video, there's no clear winner, and it seems like they are trading blows.

Size and Weight Concerns

The new 40mm lens is notably bigger and almost twice as heavy as the 35mm counterpart, weighing around 1.2 kilos or about 2.6 pounds. This size and weight difference is noticeable during use, which can be a concern, especially for street photographers who prefer a more inconspicuous setup. Paired with the Sony a7 III, the lens suffers from an issue where it goes lower than the camera body, causing problems with longer tripod plates. Moreover, the lens feels front-heavy and makes shooting one-handed or using back-button focus nearly impossible. Despite these size-related downsides, it is worth noting that the lens is Sigma's first Art lens to be completely dust and splash-proof, offering optical performance comparable to high-end cine lenses, and retains a mechanical focusing ring for smooth and accurate focus pulls.