Calculation of aperture

The f-number scale increases by multiples of

$\sqrt{2}$

(approximately 1.414) because doubling or halving the light entering the camera requires doubling or halving the area of the circular aperture, not its diameter. 

Here is the simple mathematical breakdown of why this happens: 

1. Light and Area

The amount of light that passes through a lens depends entirely on the area (A) of the optical opening. Since the aperture is a circle, its area is calculated using the formula:

 

This shows that the area (

$A$

) is proportional to the square of the diameter (

$D^2$

).

2. The Inverse Relationship

From your previous formula, the diameter is

. This means the f-number (

$N$

) is in the denominator. 

• To let in half the light, you need half the area.
• To get half the area, you must reduce the diameter by a factor of
  

  $\sqrt{2}$
  .
• Because
  

  $N$
  is inversely proportional to
  

  $D$
  , you must multiply the f-number by
  

  $\sqrt{2}$
  to make the opening smaller by that exact ratio.

Google Gemini

Let 焦距 (f) be 35 mm and F值 (N) = 2

光圈孔直徑 (D) = f / N

D = 35 mm ÷ 2 = 17.5 mm

A = 3.1416 * 8.75mm * 8.75mm = 240.5 mm square

0.5 A = 3.1416  * r * r = 120.3 mm square

r * r = 38.3 mm square

r = 6.2 mm

Original diameter is 17.5mm

Area in half, new diameter is 12.4mm

D = f / N

12.4 = 35 / N

N = 2.8

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Achilles tendon

Achilles：希臘英雄阿基里斯（Achilles），他全身刀槍不入，唯獨腳踝是弱點。

是人體最強壯、最厚的腱，但也容易受傷（例如運動員的「阿基里斯腱斷裂」）。

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Keep yourself busy

if somebody/something works or happens in tandem with somebody/something else, they work together or happen at the same time

The Central Executive Network (CEN), also called the Frontoparietal Network, is a large‑scale brain system responsible for executive functions like working memory, decision‑making, and goal‑directed behavior. It is mainly anchored in the dorsolateral prefrontal cortex and posterior parietal cortex. 

ponder: to think about something carefully for a period of time

see-saw:  a piece of equipment for children to play on consisting of a long flat piece of wood that is supported in the middle. A child sits at each end and makes the see-saw move up and down.

The Salience Network (SN) is a core brain system that acts like a “switchboard,” helping you detect important internal and external stimuli and decide whether to engage the Default Mode Network (DMN) or the Central Executive Network (CEN).

salience: ​the quality of being particularly important or easy to notice

revert to something: to return to a former state; to start doing something again that you used to do in the past

dismantle something: to end an organization or a system gradually in an organized way

Emerging evidence means new, freshly uncovered, or developing facts and data that support a specific trend, hypothesis, or shift in clinical, scientific, or social understanding.

render: to cause somebody/something to be in a particular state or condition

vivid: (of memories, a description, etc.) producing very clear pictures in your mind

utmost: greatest; most extreme

unapologetically: without saying or showing that you are sorry about something, even in situations in which other people might expect you to

notable: deserving to be noticed or to receive attention; important

confines: limits or borders

Nicole Vignola "Rewire"

hk.dictionary.search.yahoo.com

oxfordlearnersdictionaries.com

dictionary.cambridge.org

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Dreaming again

Canon EOS R8 Mark II is an entry level camera. RF 24‑105mm f/4L is a luxury lens. Although lens is more important than body, is it worthwhile to buy a luxury lens for an entry level camera?

This is a really thoughtful question — and it touches on one of the most debated topics in photography: is it better to invest in the lens or the body?

Lens importance: The lens defines sharpness, contrast, color rendering, and bokeh. A high‑quality lens like the RF 24‑105mm f/4L IS USM will deliver professional‑grade results even on an entry‑level body.

Body importance: The camera body contributes sensor performance, autofocus speed, ergonomics, and video features. But bodies evolve quickly — today’s “entry‑level” R8 Mark II already has IBIS, advanced AF, and strong video specs.

Yes, it’s worthwhile if you see photography as a long‑term pursuit. The lens will outlast the body and can move with you when you upgrade to R6 Mark III or R7 later.

No, it’s less worthwhile if budget is tight and you mainly shoot casual travel or family photos — in that case, the RF 24‑105mm STM (~395g, cheaper) gives good results without overspending.

Canon EOS R8 Mark II body is indeed lighter than the RF 24‑105mm f/4L IS USM lens. The center of gravity shifts forward. This is common with mirrorless cameras, since bodies are designed to be compact while pro lenses remain substantial.

Balance: You’ll feel the weight in your left hand supporting the lens, not in the grip. A wrist strap or tripod helps for long sessions.

Image quality: The L‑series optics more than compensate for the imbalance — sharper, better contrast, weather‑sealed.

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太空軍備競賽

The U.S. Space Force just made history: Air Force Secretary Troy Meink publicly confirmed for the first time that the U.S. has deployed on-orbit space weapons to defend against hostile adversaries. This marks a major shift in U.S. military transparency and could accelerate an arms race in space.

adversary: a person that somebody is opposed to and competing with in an argument or a battle

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www.oxfordlearnersdictionaries.com

Prime lens

大光圈定焦鏡雖然提升低光能力，但景深淺、只能把焦點放在某一位置、背景會模糊。

攝影時的直接調整（最推薦先嘗試）

• 縮小光圈：把 f/2 改為 f/2.8 或 f/4 可顯著增加景深。若光線不足，可同步提高 ISO 或放慢快門（注意手持極限）。適用於可控制曝光或靜態場景。
• 拉遠距離 / 改變構圖：把相機往後退、或讓被攝體離背景更近／遠，能改變景深感與背景模糊程度。這是最不破壞畫質的方式。

大光圈定焦鏡提供的是「畫面語言與光學特性」而非單純的曝光補償。

低光手持能力：即使有三腳架，很多場景需要手持快速反應（街拍、活動），大光圈能讓你用更低 ISO 或更快快門。

創作限制促進進步：定焦限制你移動與構圖，反而能鍛鍊視覺判斷與主題處理。

體積與重量：某些大光圈定焦比高端變焦更輕便，長時間外拍更省力。

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