If the newly announced Sigma 50mm f/1.4 DG HSM performs at a level with the Sigma 35mm f/1.4 DG HSM, then it might turn out to be my 50mm autofocus lens of choice, the manual focus Zeiss Otus 55mm f/1.4 Distagon being my #1 normal lens, and a lens unrivalled by any other normal lens.
The MTF chart for f/1.4 shows high central contrast which drops off steadily to the edges and corners. At least at the center, it should perform extremely well, but note that 30 lp/mm (green lines) cannot be compared directly to the 40 lp/mm used in Zeiss and Leica MTF charts, nor is the spectral weighting designated. Moreover, Zeiss charts are measured results from real lenses (not computed idealizations).
The drop-off away from center is likely due to increasing aberrations off-center, but it could also be a field curvature effect. Probably some of both.
Regrettably there is no f/4 MTF chart to yield an idea of across the frame behavior when stopped down. That absence is odd given the recent Sigma commitment to delivering diffraction-incorporating MTF charts, diffraction being a non-issue at f/1.4 and being most relevant when stopped down to f/4 and beyond. Moreover, Sigma has not made clear whether the chart is a measured MTF of a real production lens, or a computed result from the lens design, e.g. real lenses have production variances.
Features and specifications
Sigma calls out some appealing qualities:
● Astonishing rendering performance — Utilizing know-how and the latest design technology accumulated through the past developments, it corrects the aberration thoroughly and achieves high resolution and astonishing rendering performance even near the edge of the image.
● Achieving both high resolution and beautiful bokeh — While pursuing a high level of resolution on the focused point, bokeh in front and behind the point of focus is carefully maintained to have soft rendering. Aberrations including sagittal coma flare and color distortion that affect the image quality are thoroughly corrected. From open aperture, high-definition rendering without blur is achieved. Moreover, by ensuring vignetting at the minimum and preventing color blur around the front and back of the focus point, it also achieves natural bokeh.
● Excellent correction of sagittal coma flare — It is ideal for a wide aperture standard lens to have a high rendering performance from open aperture throughout the entire image. For instance, the molded glass aspherical lens elements provide excellent correction to sagittal coma flare. It is perfect for astronomical photography and shooting of illumination because of the reduced blur on the point light sources near the edge of the image. It also creates an attractive bokeh in portraits and indoor shooting.
● Correction of axial chromatic aberration — For axial chromatic aberration that is hard to correct even during the image processing, SLD (Special Low Dispersion) glass elements are incorporated, ensuring high image quality throughout the entire focusing range. The lens achieves sharp and high contrast image rendering.
● Minimized distortion — It is not possible to compensate for distortion just by changing the aperture values. Thus, the lens development stage was vital in ensuring minimized distortion. The "SIGMA 50mm F1.4 DG HSM" has positioned each glass element to optimize the power layout at respective positions, and succeeded in minimizing distortion.
● Rich peripheral brightness — It secures very rich brightness in the peripheral areas, which can be a common problem for a lens with a large diameter. By positioning wide elements in the front group, it has improved the efficiency at large apertures. Since it is capable of minimizing vignetting, very clear depiction across the image is ensured.
● Designed to minimize flare and ghosting — Flare and ghosting were thoroughly measured and monitored from the lens development stage to establish an optical design which is resistant to strong incidental light such as backlight. The Super Multi-Layer Coating reduces flare and ghosting and provides sharp and high contrast images even in backlit conditions.
● Minimum focusing distance of 40cm — The lens incorporates a floating system that adjusts the distance between lens groups while focusing, thereby reducing the amount of lens movement required. This achieves a minimum focusing distance of 40cm and maximum magnification ratio of 1:5.6. As there is less variation in aberration at different shooting distances, the lens delivers high rendering performance throughout the entire focusing range.
3. Hyper Sonic Motor ensures High AF Speed — The HSM (Hyper Sonic Motor) ensures a silent, high-speed AF function. Optimizing AF algorithm, smoother AF is achieved. It also enables full-time manual focusing capability which allows sensible focus adjustment by simply rotating the focus ring.
● Incorporating Rounded Diaphragm — The 9 blade-rounded diaphragm creates an attractive blur to the out-of-focus areas of the image.
|Focal length:||50mm (nominal)|
|Aperture scale:||f/1.4 - f/16, rounded diaphragm blades|
|Focusing range:||40cm / 15.7in|
|Image ratio at close range:||1:5.6|
|Number of elements/groups:||13 elements in 8 groups|
|Dimensions:||85.4mm x 99.9mm / 3.4in. x 3.9in|