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. 👍 Thanks for watching! Please like, comment, & subscribe. ============================= Table of Contents: ============================= 0:00 - Intro 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! ============================= Gear I Use to Make Videos: ============================= https://kit.co/GeraldUndone/youtube-video-gear ============================= Best Deals for Camera Gear ============================= Gear Focus Marketplace: https://geni.us/gearfocusGU Amazon Top Deals: https://amzn.to/3d9tdT4 B&H Deal Zone: https://bhpho.to/2SCDrnj ============================= Music: ============================= I use Artlist for my background music needs. Use this link to get two extra months when signing up: http://bit.ly/2TV5sYT ============================= Follow Me: ============================= Twitter: https://twitter.com/GeraldUndone Instagram: https://www.instagram.com/geraldundone Discord: https://discord.gg/xT2HNKw ============================= Patreon & PayPal: ============================= If you wish to support the channel monetarily, you can use my Patreon page here: https://www.patreon.com/GeraldUndone Or directly via PayPal here: https://www.paypal.me/geraldundone This is appreciated, but unnecessary, and no content will ever be behind a paywall. ============================= Affiliate Links: ============================= Some of the links in my video descriptions are affiliate links, which means at no extra cost to you, I will make a small commission if you click them and make a qualifying purchase. If you have a different purchase in mind, you can also use these storewide links below. 🛒 Amazon: http://geni.us/1m1G32 🛒 B&H Photo: https://bhpho.to/2MYRKBE ============================= Recommended Channel Tools: ============================= 💬 Closed captioning provided by ONEXTRA: https://onextra.ca/ 🚩 If you're a fellow YouTuber, I highly recommend you try TubeBuddy. It's helped my channel immensely: https://www.tubebuddy.com/pricing?a=Undone ============================= #flash #photography #guide