Sony ALCSH0006 Aspherical lens elements ED and Super ED glass, Rear focusing mechanism, STF lens

A lens technology

The technology required to produce first-class interchangeable camera lenses is very sophisticated indeed, and that applies to every phase of the production process from design through precision parts manufacturing and assembly to stringent quality assurance testing and more. Sony brings a distinguished history of excellence in all of these areas to bear in producing the A lenses. You’ll feel the difference in the way A lenses handle, and you’ll see the difference in the superior image quality they deliver.

Internal focusing mechanism	SAM (Smooth Autofocus Motor)
In this type of lens, focusing is achieved by moving only the internal elements.	SAM is another type of internal lens motor for autofocus drive. While the SSM
The overall length of the lens remains constant, and the filter mounting	motor described above is piezoelectric, the SAM motor is electromagnetic in
thread at the front of the lens remains stationary during focusing.The latter	operation, but provides similar benefits: responsive autofocus operation that
characteristic is an advantage when using a polarizing filter. Other advantages	does not require mechanical coupling from the camera body.
include fast autofocus response and reduced minimum focusing distances.

Aspherical lens elements	ED and Super ED glass
Spherical aberration, slight misalignment at	Chromatic aberration in conventional
the image plane between light that has passed	optical glass elements can reduce contrast,
through the center and periphery of a simple	resolution, and color fidelity, particularly at
spherical lens, can become a noticeable	longer focal lengths. ED (Extra-low Dispersion)
problem in large-aperture lenses.The most	and Super ED glass were developed with
effective solution is to use one or more specially	refractive index and dispersion characteristics
shaped aspherical elements near the aperture	specially tailored to counter this problem.
stop to restore perfect alignment at the image	Lenses that include ED or Super ED glass
plane, thus maintaining high contrast even	elements provide superior contrast and
with the aperture wide open.Aspherical lenses	resolution throughout the image even at
arranged far from the aperture stop can minimize image distortion and flatness	large aperture settings.

of the image plane.Well-designed aspherical lens can reduce the number of elements in the lens for less overall size and weight.

Spherical lens		Aspherical lens		Conventional glass	ED glass	Super ED glass
	Image		Image
	sensor		sensor
	plane		plane
				Image sensor	Image sensor	Image sensor
				plane	plane	plane
Auto clutch				Floating lens mechanism
The auto clutch mechanism decouples the focus ring so that it does not				This focusing feature is particularly important in certain lenses that are
rotate during autofocus operation.This allows the lens to be cradled in one				designed for close focusing. It maintains optimum lens performance and
hand without interfering with autofocus operation, for improved shooting				therefore maximum sharpness right down to the minimum focusing distance
comfort and versatility.				by moving “floating” elements independently when focusing, rather than
				moving the entire optical assembly as a whole.

Rear focusing mechanism

This focusing configuration has similar advantages to internal focusing, described above, but focusing is achieved by moving the rear lens elements rather than the internal elements.

SSM (Super Sonic wave Motor)

SSM is an advanced direct-drive piezoelectric motor that is capable of delivering high torque even at low speeds, with almost instantaneous start/ stop response. Its fast response and low-noise operation translate directly into quick, quiet autofocus operation. SSM lenses also include position detection for enhanced focusing precision. Other advantages of this advanced drive system are that the focus ring does not rotate during autofocus operation, and you can directly switch to manual focusing by simply rotating the focus ring.

			Piezoelectric
		AC voltage,	element
			Stator
		Phase B
			Rotor
		AC voltage,
Rotor	Stator	Phase A

STF lens

A unique A lens feature currently available only in the SAL135F28, STF

(Smooth Trans Focus) is an optical technology that is aimed specifically at creating the smoothest, most visually pleasing defocusing effect possible while retaining full resolution and contrast at in-focus areas. STF technology employs a special “apodization” element that causes the intensity of defocused point light sources to fade out radially so that no sharply defined edges or geometry remain.The result is extraordinarily creamy defocusing that goes beyond the capabilities of conventional lens technology.

STF lens

Apodization optical element

A a

b c

Defocusing of STF lens

(around focus point “a”)

Conventional lens

A a

Circular aperture

Standard lens apertures appear as a flat-sided polygon when the lens is stepped down, the number of sides corresponding to the number of blades in the aperture.This results in the familiar polygonal out-of-focus highlights seen in many photographs. Almost all A lenses feature a unique circular aperture that contributes to smooth, natural defocusing.

Comparison of aperture design

Conventional aperture Circular aperture

Focus hold button

Press this button to lock focus at the current setting.The focus hold button is on the lens barrel right under your fingertip for convenient, fast operation.

Focus range limiter

This feature can be used to limit focus range when you need the quickest possible autofocus response. On some lenses a single “limit” range will match the characteristics of the lens (near focus limit on macro lenses, for example), while some lenses have a “near/far” limit range switch.

SSM consists of a rotor (left), and a stator (right) on which plexoelectric elements are mounted.

b c

Defocusing of conventional lens (around focus point “a”)

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