This full-frame ZEISS Vario-Sonnar wide-angle zoom lens covers a 16mm to 35mm range with a constant maximum aperture of F2.8, enabling consistent depth of filed and exposure settings at any focal length. The high-performance optical design boasts ZEISS T (T-star) coating for superior contrast and resolution, three aspherical elements with outstanding surface precision for low distortion and corner to corner sharpness - even at wide-angles, plus 1 ED (Extra-low Dispersion) glass elements and 1 Super ED element to reduce chromatic aberration to an absolute minimum. The SAL1635Z2 employs Sony's SSM (Super Sonic Wave Motor) for extremely fast and accurate AF (auto focus). Silent AF and iris (aperture) drive is employed for movie capture and a 9-blade circular aperture for beautiful defocussed backgrounds. Ideal for Full-Frame and APS-C E-mount cameras.

Unmatched ZEISS T (T-star) coating
Coated optics were pioneered by ZEISS - and this superb lens features the ZEISS T (T-Star) coating that virtually eliminates lens flare, internal reflection and light scattering that can otherwise occur at glass-to-air surfaces. The T coating contributes to outstanding image quality, with high contrast and uniformly excellent resolution right out to the image edges. Not simply applied to any lens - the T symbol only appears on multi-element lenses in which the required performance has been achieved throughout the entire optical path, therefore guaranteeing the highest quality.

Circular Aperture
When changing your aperture to defocus the background, the light sources appear blurred. This 'bokeh' effect of the blurred background can be enhanced with circular aperture blades used in this lens. Conventional aperture blades have flat sides creating unappealing polygonal shaped defocussed points of light. Circular aperture overcomes this problem through the use of curved blades that keeps the aperture almost perfectly circular from its wide-open setting to when it is closed.. Smoother, more natural defocusing can be obtained as a result.

Aspherical lens elements
Aspherical lens design dramatically reduces spherical aberration while also reducing lens size and weight. Spherical aberration is a slight misalignment of the light rays projected on the image plane, caused by differences in refraction in conventional spherical lenses which degrade image quality in large-aperture lenses. Specially shaped "aspherical" elements near the diaphragm restore alignment of light rays at the image plane, maintaining high sharpness and contrast even at maximum aperture and can also be used at other points in the optical path to reduce distortion. Well-designed aspherical elements often requires complex glass molding technology, but can reduce the total number of elements required, thus reducing overall size and weight.

ED (Extra-low Dispersion) glass
As focal lengths get longer, lenses built with conventional optical glass have difficulties with chromatic aberration, and as a result images suffer from lower contrast, lower color quality, and lower resolution. ED glass dramatically reduces chromatic aberration and provides superior contrast across the entire image, even at large aperture settings. Super ED glass provides enhanced compensation for chromatic aberration.

SSM (Super Sonic wave Motor)
SSM is a piezoelectric motor that contributes to smooth and silent AF operation. The motor produces high torque at slow rotation, and provides immediate start and stop responses. It is also extremely quiet, which helps keep autofocusing silent. Lenses that feature SSM also include a position-sensitive detector to directly detect the amount of lens rotation, a factor that improves AF precision overall.

Dust and moisture resistant design
The dust and moisture resistance design makes this lens appropriate for heavy-duty outdoor use, especially when combined with a camera that employs weather resistant measures such as the Sony's a7 series of cameras.

Internal focusing
Only the middle groups of the optical system move to achieve focus, so the overall length of the lens does not change when focusing. Other important benefits include fast autofocusing and a short minimum focusing distance. Also, the filter thread at the front of the lens does not rotate, which is convenient when using a polarizing filter.

Focus hold button
Once you've adjusted focus to where you want it, pressing this button on the lens barrel will keep the lens locked to that focusing distance. The preview function can also be assigned to this button through the camera's custom settings.

Distance encoder
The distance encoder plays an integral part in ADI flash metering, which delivers high precision flash metering that is unaffected by the reflectance of subjects or backgrounds. The distance encoder is a lens component that directly detects the position of the focusing mechanism, and sends a signal to the CPU in order to measure distance to the subject. During flash photography, this data is very useful in calculating how much flash output is appropriate to the scene.

ADI flash metering
Advanced Distance Integration flash metering is available when the built-in flash, or HVL-F60M / HVL-F43M/ HVL-F32M / HVL-F20M external flash is used together with a lens that has a built-in distance encoder. It provides automatic metering that is virtually unaffected by the reflectance of subjects or backgrounds. Precise distance information is obtained through the encoder, and this data is used to compensate the flash output accordingly. This yields good exposures more reliably than conventional TTL (through-the-lens) flash metering, which can be thrown off by overly reflective or overly dark subjects and background.

Features:

• ZEISS T coating delivers superior contrast and resolution
• Constant F2.8 max aperture maintains exposure / depth of field
• 3 Aspherical lenses for low distortion and corner sharpness
• 2 Extra Low Dispersion elements reduce chromatic aberration (1 Super ED)
• Silent AF and iris (aperture) drive ideal for movie capture
• Dust and moisture resistant design for maximum durability
• 9-blade circular aperture for beautiful defocussed backgrounds
• Ideal for Full-Frame and APS-C A-mount cameras
• Improved Internal focusing system - 4x faster subject tracking

Specifications:
Optics/Lens
- Lens Type: 35mm full frame
- Lens Mount Type: Sony A-mount
- Aperture: Circular
- Aperture (Max.): f/2.8
- Aperture (Min.): f/22
- Focal Length (35mm equivalent): 16 - 35mm (35mm) 24 - 52.5mm (APS-C)
- Filter Diameter: 77mm
- Lens Groups-Elements: 17 elements, 13 groups
- Minimum Focus Distance: 0.92' 0.28m
- Angle of View: 83 degrees - 44 degrees (APSC) 107 degrees - 63 degrees (35mm)
- Aperture Blade: 9 blades
- Distance Encoder: Yes
- Maximum Magnification: 0.24x

Weights and Measurements
- Dimensions (Approx.): 3-3/8" x 4-1/2" (83 x 114mm)
- Weight (Approx.): 30.8 oz (872g)