science

Sigma SA-mount

Sigma SA-mount is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Sigma SA-mount rather than just read about it. In short: The Sigma SA-mount is a lens mount by the Sigma Corporation of Japan for use on their autofocus single-lens reflex and mirrorless cameras. It was introduced with the SA-300 in 1992.

Key takeaways

Sigma SA-mount belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Sigma SA-mount to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Sigma SA-mount from memory before moving on to harder problems.

Reference excerpt

The Sigma SA-mount is a lens mount by the Sigma Corporation of Japan for use on their autofocus single-lens reflex and mirrorless cameras. It was introduced with the SA-300 in 1992. Originally, the SA-mount was a dual-bayonet mount with inner (SA-IB) and outer (SA-OB) bayonets, the latter being a feature intended to mount heavy telephoto lenses, but never utilized by Sigma and consequently dropped with the release of the SD14 in 2007. There were two precursors to the introduction of SA-mount cameras, the manual-focus Sigma Mark-I in 1976, which still featured a M42 screw lens mount, and the SA-1 of 1983 with Pentax K-mount. Mechanically, the (inner) SA-mount is similar to the Pentax K-mount as well, but with a flange focal distance of 44.00 mm, identical to that of the Canon EF-mount. Like the EF-mount, the SA-mount uses electrical communication between body and lens, and in fact uses the same signalling lines and protocol as the EF-mount, despite the physical incompatibility. Sigma has long produced EF-mount lenses for Canon cameras, and thus had the ability to use this protocol. All Sigma SLRs and DSLRs can use manual focus lenses too, which have no electrical communication between body and lens. In September 2018, Sigma announced that they will stop the development of SA-mount cameras and focus on the Leica L-mount, as members of the L-Mount Alliance alongside Panasonic.

Compatibility M42-mount lenses can be mounted via adapters utilizing the SA inner bayonet. Despite the physical similarities Pentax K-mount (PK) lenses can't be fitted straight onto the SA-mount as well. If the protruding AA lever and AA protector outcrop are removed, the fit is slightly loose as the SA-mount has a slightly bigger bore than the PK-mount. However, due to the difference in registration distance scale focusing isn't possible and the close focusing capabilities will be reduced. Utilizing the SA-OB bayonet mount (on camera bodies supporting it), Nikon F-mount can be fitted and used via a JTAT mount adapter developed by Kazuo Suzuki, Tachibana Seisakusho. In digital cameras, it is important to make sure that the rear of an adapted lens never hits the camera's dust protector filter when focused to infinity.

Lens adaptations Newer lenses with Sigma SA-mount can be used on newer Sony E-mount cameras (for example, the Sony ILCE-7 series, the ILCE-5000, ILCE-6000 etc.) using the Sigma MC-11 SA-E mount adapter, introduced in 2016. (A similar Sigma MC-11 EF-E adapter is available to mount Canon EF-mount lenses on Sony E-mount cameras.) The adapters support autofocus, image stabilization and electronic aperture control.

Camera bodies

Lenses All autofocus SLR lenses manufactured by Sigma since 1989 are available for the SA-mount. A partial listing can be found here.

Illustrations

Worked examples

Example 1 — a first encounter with Sigma SA-mount

Start with the simplest possible case. Write down what Sigma SA-mount claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Sigma SA-mount before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Sigma SA-mount ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Sigma SA-mount

In research: Sigma SA-mount appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Sigma SA-mount in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Sigma SA-mount is common in secondary-school and first-year university syllabi. It links to neighbouring topics Lens mounts, Sigma Corporation, so understanding it makes those chapters shorter.
In everyday life: Look for Sigma SA-mount outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Sigma SA-mount in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Sigma SA-mount means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Sigma SA-mount out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Sigma SA-mount in simple terms?

The Sigma SA-mount is a lens mount by the Sigma Corporation of Japan for use on their autofocus single-lens reflex and mirrorless cameras. It was introduced with the SA-300 in 1992.

Why does Sigma SA-mount matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Sigma SA-mount?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Sigma SA-mount.