Guide Number Misconceptions / Understanding Flash Power on Strobes & Speedlights
Explaining the math behind a flash’s guide number, how it relates to f-stop, and more practical formulas for nailing exposure on your strobes & speedlights.
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Table of Contents:
0:48 – Guide Number Formula
1:02 – Canon 600EX-RT Guide Number Explained
1:57 – Misconception: Forgetting about f/1
2:57 – Using Guide Number to Find Subject Distance
3:51 – What If the Subject Was Closer? (Inverse-Square Law)
4:48 – Practical Uses: How to Figure out Correct Flash Power
5:23 – Why Flash Calculators Don’t Solve for Flash Power
5:50 – How to Calculate Flash Power in Your Head
6:12 – Find the Correct f-stop at Full Power
6:36 – One Stop of Flash Power Equals One f-stop
6:58 – Powers of 2 Make This Even Easier
7:25 – How to Memorize All the f-stops Easily
7:44 – A Simpler Way without Memorizing Numbers – Turn the Dials!
8:08 – ISO Impact on Guide Number
8:33 – What about Shutter Speed? Does It Affect Flash Power?
8:57 – Final Thoughts: Know Your Lights!
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