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The Exposure Triangle | Day 8

cap and gown - photo credit: krisandapril on flickrDo you feel smart? We learned shutter speed controls how long we record the moment. ISO controls the flow of the water, or the receptibility of our sensors. Aperture is determined by the lens and can control both the amount of light we allow in and the depth of field.

Auto mode ends here, my friends. You’re officially too educated to have an excuse to rely on it. If this were school, you’d be graduating grade school and moving to a new campus with the big kids. Let’s throw our caps in the air!

How do we put it all together?

I want to explain this carefully without sounding like the grownups on Charlie Brown. Wah-wahwah-wah-wah-wah.

This is where I assign you to run to the library or go to amazon.com via my affiliate link and buy Bryan Peterson’s book Understanding Exposure. He wrote an entire book in what I’m going to try and explain in a couple blog posts. Peterson’s book is the bible of exposure – and a must read to handle shooting confidently and in full control of your camera.

Exposure Triangle

I read this analogy a long time ago, and I wish I knew where so I could credit it – and if any of you know, link it and I’ll come back and credit the rightful owner. But I think this analogy has been around the block a few times. It’s a great example to show how the three are interconnected, and totally reminds me of being 16 again.

Putting together the 3 elements of exposure can be explained much like a sunbather trying to get a sun tan. The sunbather wants the right amount of sun to get some color, but not too much and burn. (Back in the day, it was cool to layout in the sun – this was before spray tans. I cringe now thinking of tanning beds and baby oil! Ack!)

In this analogy the three elements are:

  • skin type – Olive skin people have better receptors to sunlight than fair skin people. Kinda like ISO.
  • sunscreen lotion – How much you put on controls how many rays get through. Kinda like aperture.
  • length of time in the sun – How much color you get can be determined by how long you’re exposed to the sun, like shutter speed.
  1. If you change how much sun lotion you have on, it changes how long you can be in the sun.
  2. If you have olive skin you can be in the sun longer than your fair skinned friends whose skin is more sensitive to sunlight.
  3. If you’re hardly wearing any sunscreen and you’re fair skinned, you can only be exposed to the sun for a a tiny bit of time.
  4. If you’re wearing strong sunscreen and you’re fair skinned, you can stay longer because fewer rays get through.
  5. If you’re olive skinned you can stay in the sunlight longer, even without sunscreen.
  6. Add sunscreen to olive skin and you can be exposed to sunlight for the longest.
  7. If you are fair skinned and your friend is olive skinned, to stay in the sunlight for the same amount of time, you need a lot more sunscreen for the same exposure.

Let’s translate the above, line by line, to photography terms:

  1. If you change your aperture, it changes how long you leave your shutter open.
  2. If you shoot on a low ISO you can leave your shutter open longer than shooting with a high ISO, because high ISO is more sensitive.
  3. If your aperture is wide open, you can only open the shutter for a tiny bit of time.
  4. If you make your aperture smaller, you can open your shutter for longer, because less light gets through the opening.
  5. If you shoot at an ISO of 100 you can shoot a longer exposure, even with the aperture more open.
  6. Low ISO and small aperture means the longest shutter speed.
  7. At an ISO of 100 and an ISO of 400, to get the same exposure, the aperture needs to be a lot more open for ISO 100 than 400.

What this means is that your high school math teacher was right when he said, “You will use math your whole life.” Photography is kinda mathy. (<----- Insert groans here.) The good news is it's mostly only doubling or halving. And there are scales that have these halving and doubling stops laid out for you. Come back tomorrow and we'll do math. Now doesn’t that sound super fun?

Don’t forget about my girls who are sharing this 31 Days journey with us:

31 Days of Grace :: Chatting at the Sky
31 Days to an Inspired Table :: My First Kitchen
31 Days to a Less Messy Nest :: Nesting Place
31 Days of Living Simply :: Remodeling This Life
31 Days of Autumn Bliss :: The Inspired Room
31 Days to More. . .With Less :: Beauty and Bedlam
31 Days to a Better Photo :: My 3 Boybarians
31 Days to Stress Free Entertaining :: Reluctant Entertainer


  1. I am so enjoying this, Darcy! I took forty pictures of an orange today and finally got the tea cup in the background blurry. Success! thanks for the easy to understand info 🙂

  2. I just wantd to say THANKS for these very interesting and understandable series of postings! Unfortnately I haven’t had the time to test yet, but will sue do! Once again: thanks!

  3. Thank you, thank you, thank you! I only found you today so I haven’t had a chance to try any of this out yet, but I will be setting up camp on your blog for the rest of the month (and probably longer, lol) and eagerly awaiting the next part =D I’ll be getting cozy with my manual tonight thats for sure!

  4. I am loving your series!
    I so wish my high school photography teacher would have used the sunbathing analogy! It would have saved me from a D in that class.

  5. I am so loving this series, Darcy!!

    I had a total lightbulb moment while scouring David Busch’s Canon 40D Guide to Digital Photography and Bryan Peterson’s Understanding Digital Photography book while we drove through Yellowstone. I knew that the exposure meter needed to be at 0, but for the two years prior, I’d been trying to figure out how to turn IT to zero and make it stay there. I was so frustrated, because I’d just taken about 25 photos at a lake and they were all at -2. I knew I would be trapped on automatic forever if I didn’t figure it out, and I didn’t have internet access. Finally, with 2 or 3 books on my lap, and while reading aloud to my husband and trying to talk through what I was reading verbally, everything came together and I realized that when the exposure meter moved, it was trying to tell me that something else needed to be changed. All this time, I thought it was another one of the functions like ISO, shutter speed, and aperture. When I realized it was the meter that showed whether those three settings equated a proper exposure in the current conditions, I WAS ELATED. Finally, I have the confidence to move to the manual settings! Did I mention that I’ve had my DSLR for 2 1/2 years?!? I have read my manual, have worn-out by Canon 40D book, read countless books from the library, and many blogs; I don’t know why I didn’t figure this out much sooner, especially since all I would have had to do was watch this little video: http://www.ehow.com/video_2369634_canon-eos-40d-manual-exposure.html But now that I did…what’s the easiest way to correct photos that have been underexposed?

    • Day 10 covers EXACTLY this! 😉

      I hope I have already answered those questions in that post, but if not – let me know.

  6. Thank you for this series, I imagine it’s taken a lot of time to prepare. I’ve learnt so much in these last 8 days. I’ve gone from completly overwhellemed to feeling like I’m starting to understand it all in just a few days. I have a couple of photography books I’ve tried to read in the past but ended up more confused, they’re making much more sense now! I’ve ordered the book on exposure on your recommendation. Thank you again. Looking forward to the rest of this series.

  7. I think I’m going to print all these tutorials and put them in a binder. Yesterday my daughter had a soccer game at 5:00 and it ended at 6:30ish. This makes for tricky photography because of the sun going down sooner and not enough light. I took that opportunity to “practice” in the manual mode. The results weren’t too bad. Still needs work but at least I’m trying it and I think it also goes along with the camera I have (a Nikon D50) which just doesn’t have as many capabilities as the newer ones (which I’m also looking into).

    I also enjoyed reading about the equipment you use. I had to wipe drool off my keyboard (C:

  8. O my goodness, I can’t believe I turned down “understanding exposure” for “understanding close-up photography” by the same author. I guess I will have to go out and find me that book. Thanks Darcy! I’m glad I’m all catched-up now!
    See ya tomorrow. 🙂

  9. aww mom, don’t make us do math.

  10. “Photography is kinda mathy.” **groan** 🙂

    In one simple post, you made everything completely “click” for me! I have read and reread Understanding Exposure and my manual and I still couldn’t get “it” (whatever that was). I thought I understood things separately but just couldn’t put it all together. I also had no clue how to see when my camera said my shot was at a “correct exposure” as Bryan Peterson’s book kept saying.

    Thanks so much for your hard work on these! It’s awesome! Since going though most of your 31-day posts, I’ve been shooting manual and *loving* it!


  11. My head hurts. But I’ve learned so much already, thank you for this awesome tutorial!


  1. […] the exposure triangle, how those settings overlap and interact. Learn your in-camera meter and when to trust it, and when […]

  2. […] The Exposure Triangle […]