engineering

Jun Hirakawa

Jun Hirakawa is a engineering 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 Jun Hirakawa rather than just read about it. In short: Jun Hirakawa (平川純) is a Japanese lens designer best known for creating the Pentax FA 43mm Limited and FA 77mm Limited lenses during his time at Pentax. Hirakawa said at the time that he regretted his "early retirement" from Pentax in 2010, around the time that Hoya acquired the company, and was subsequently hired by Tamron.

Key takeaways

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

Reference excerpt

Jun Hirakawa (平川純) is a Japanese lens designer best known for creating the Pentax FA 43mm Limited and FA 77mm Limited lenses during his time at Pentax. Hirakawa said at the time that he regretted his "early retirement" from Pentax in 2010, around the time that Hoya acquired the company, and was subsequently hired by Tamron.

List of credited lens designs Hirakawa is credited with designing:

DA 10-17mm f/3.5-4.5 Fisheye (co-developed with Takayuki Ito) DA 14mm f/2.8 DA 40mm f/2.8 Limited (based on the smc PENTAX-M 1:2.8 40mm) DA 50-200 f/4-5.6 smc DA 55-300mm F4-5.8 ED DA* 55mm f/1.4 F 17-28mm f/3.5-4.5 Fisheye F 35-80mm f/4-5.6 F* 600mm f/4 FA 28-105mm f/4-5.6 FA 28mm f/2.8 AL FA 28mm f/2.8 SOFT FA 35mm f/2 FA 43mm Limited FA 70-200mm f/4-5.6 FA 77mm Limited (based on the smc PENTAX-A* 1:1.4 85mm) FA* 24mm f/2 FA* 80-200mm f/2.8 FA* 85mm f/1.4 FA* 600mm f/4 Tamron SP 24-70mm f/2.8 (2011) Unreleased 31mm f/2.4 prototype for the FA Limited series Unreleased wide-angle (80mm on 6x7 or 65mm on 645) f/2.8 (1986) Unreleased 70-300mm f/4-5.8 (1987) Unreleased 100-400mm f/5.6 (1992, with Koichi Maruyama) Unreleased 400mm f/4.5 (1988)

References

External links 平川純 on LinkedIn Hirakawa, Jun (January 2000). "レンズテクニカルレポート SMCペンタックスFA77mmF1.8リミテッド FA43mmF1.9リミテッド" [Lens technical report. SMC Pentax FA77mm, F1.8 Limited and FA43mm, F1.9 Limited.]. Photographic Industries. 58 (1): 78–81. Retrieved 8 November 2017. Nyquist, Greg (18 August 2012). "Lessons from a Legendary Lens Designer". The Northcoast Photographer (blog). Retrieved 7 November 2017. Hirakawa Jun on Camera-wiki.org Hirakawa patents on patentgenius.com

Worked examples

Example 1 — a first encounter with Jun Hirakawa

Start with the simplest possible case. Write down what Jun Hirakawa claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, 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 Jun Hirakawa 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 Jun Hirakawa 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 Jun Hirakawa

In research: Jun Hirakawa appears in engineering 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 Jun Hirakawa 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: Jun Hirakawa is common in secondary-school and first-year university syllabi. It links to neighbouring topics Japanese engineer stubs, Japanese industrial designers, Lens designers, so understanding it makes those chapters shorter.
In everyday life: Look for Jun Hirakawa 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 Jun Hirakawa in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Jun Hirakawa 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 Jun Hirakawa out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Jun Hirakawa in simple terms?

Why does Jun Hirakawa matter?

Because it connects several engineering 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 Jun Hirakawa?

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 Jun Hirakawa.