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Understand Exposure in Under 10 Minutes


DPS-Annie-Tao-Exposure-article-perfect-exposure-exampleThere are countless Photography books and classes that explain exposure, yet after reading or attending them, your photos may not have improved because…well, let’s be honest… some of us Right-Brainers aren’t super technical!

I recently taught a small photography class to newbies. I thought hard about how I could explain exposure in the simplest way possible. I found that a parallel example of something relatable was the best way to convey the different aspects that impact exposure.

I tested this theory by explaining exposure to my 8-year old daughter and then quizzed her. She proved the theory was a success by grasping the concepts within 10 minutes. So I’d like to share my lesson with you so you can understand exposure in under 10 minutes!

A 10-minute lesson that will change your Photography

Your DSLR camera is like your head with the LENS being your vision and the camera BODY is your brain. Your vision sees things and your brain records the details.


Just like when you look at something – let’s say, a flower – your eyes see it and send information to your brain that the flower has long petals and that it is yellow. If you looked at it too quickly or it was too dark, for example, the information your brain records is compromised.

The “exposure triangle” is about how 3 things — aperture, shutter speed and ISO — work together to provide enough light for your brain (the camera) to record what you see. You need the right combination of these 3 components to have perfect exposure.


Good exposure

For example, if you don’t let in enough light, you won’t see things very well because it’ll be too dark (underexposure).


Too dark, or underexposed

If you let in too much light, then it’ll be too bright and you can’t see a lot of the details (overexposure).


Too bright, or overexposed

APERTURE = how WIDE you open your eyes

A small aperture (a large f-stop or f-number, like f/22) is like squinting. A large aperture (a small f-stop or f-number, like f/1.4) is like having “bug eyes”.

Quiz:  If you are shooting in low light, how wide do you open your eyes? Will you see well at night if you are squinting (small aperture)?

Quiz:  What happens on a super bright day if your eyes are wide open and they’re open for a long time (slow shutter and large aperture)? Can you see well then?


Aperture is how wide you open your eyes – bug eyes, or squinting

SHUTTER SPEED = how LONG you open your eyes

A fast shutter, like 1/1000th of a second, is blinking super fast. A slow shutter speed, like 2 seconds, is keeping your eyes open and then blinking. The thing to remember is:  your brain is recording everything when your eyes are open. So if you or something you’re looking at is moving, and your eyes are open a long time (slow shutter), then your brain will record a blurry image.

Quiz:  If you want a crisp shot of someone jumping, how long do you need your eyes open? What will freeze the shot:  a quick blink (fast shutter) or a slow one (slow shutter)?


ISO = special glasses

ISO = special glasses that help you see in the dark

ISO is like the opposite of sunglasses. Let’s call them MOONglasses!  😉

The higher the ISO, the thicker your moonglasses, so the more you are able to see in low light. You need thick moonglasses (high ISO) when shooting indoors or at dusk. You need very thin moonglasses (low ISO) when it’s a sunny day.

Quiz:  do I need thick, thin or medium moonglasses if I’m shooting at the beach on my lunch break?

All 3 of these things work together

Here is an example:  You are photographing your sleeping cat who is snuggled on the couch. There is not much light coming through the windows or additional ambient light. To see well, you have medium-to-thick moonglasses on (such as ISO 600). You need to have your eyes open pretty wide (large aperture, such as f/1.4). However, you don’t have great vision (you have a kit lens that only goes up to f/4.5), so you need more light to see. Thus, you leave your eyes open longer (slow shutter speed, such as 1/30th sec).

Final Quiz:

  1. In the same scenario, your cat notices you are snapping photos, so she starts walking away and leaps off the couch. You still want to photograph her. Which would you change:  how open your eyes are (aperture), how long you leave your eyes open (shutter speed), or thickness of your moonglasses (ISO)?
  2. If you increase your shutter speed because you want to freeze the image, what else would you need to change? (If you changed nothing else, the image would be too dark because you let in less light.)

Once you get the basic concept of exposure and how the three components of the exposure triangle (aperture, shutter speed and ISO) work together, turn your DSLR camera to “manual” and practice the specific settings based on different circumstances.

Want more on exposure?  Try these:

Read more from our Tips & Tutorials category

Annie Tao is a Professional Lifestyle Photographer in the San Francisco Bay Area who is best known for capturing genuine smiles, emotions and stories of her subjects. You can visit Annie Tao Photography for more tips or inspiration. Stay connected with her on her Facebook page

  • Lorna

    Thank you. I have learned more from reading DPS in the past 2 weeks than in the last 8 years (since I got my first DSLR) I’m one of those who needs everything explained in simple terms that I can understand and this sure helps!

  • Annie Tao Photography

    I love that there are so many ways to explain the exposure triangle, and the best explanations (to me) are the ones that people can relate to, so they can more easily understand the concept. Thanks for sharing, Sheree!

  • Annie Tao Photography

    Raewyn, you crack me up!!!!

  • Annie Tao Photography

    I am so glad to hear this, Lorna! When I started out in Photography, my brain whirled with all the techno jargon that I found it hard to learn, so I learned by shooting a lot. Thus, now when I write about Photography, I make sure to write it in the simplest way possible. 🙂

  • Annie Tao Photography

    My daughter came up with that when I said ISO is the opposite of sunglasses. 🙂

  • Lisa

    I enjoyed your analogies… fun stories make it easier to remember! I have OLD brain, so photography helps those brain cells keep firing.

  • Annie Tao Photography

    I have an “old brain” too, Lisa! 🙂 Glad you found this helpful.

  • John Kessler

    Understanding exposure is the easy bit for me. I started my photography in the 35mm film days with a fully manual SLR camera. I could quickly and easily dial in any shutter speed and aperture I wanted while watching the results on an exposure meter. That camera even had a depth of field preview button which I used all the time. And of course, manual focus.

    My modern digital cameras tend to hide all of these controls behind fancy menus and “helpful” automation. It takes me forever to figure out how to do what I could do in my sleep in the old days. It’s faster and easier just to pop it into automatic mode and think about composition.

    I wish someone would make an affordable fully manual camera for us old fashioned types.

  • Rob

    I like how you explained this for beginners, Annie! Nicely written! 🙂 I would also add that it’s important not to go over 800 ISO or you will significantly increase noise in your pictures. I know cameras have gotten better at higher ISO rates, but, one does have to be careful because higher ISO rates can sometimes mean grainy images. Grainy images = unhappy clients!

    If a photographer needs great depth of field (f8 or beyond) it would be better advised for him/her to choose a much slower shutter speed for more light rather than bump up the ISO really high.

  • Annie Tao Photography

    Thanks for your addition about how higher ISO numbers = more grain. That is very true! Though I don’t mind grain at all, in fact, some images in my opinion (like contrasty BxW images) look great with more notable grain!

    I think your last point is interesting, and I think your settings depend on what you are shooting, how you shoot, and your artistic style — because, for me, I would bump up the ISO before slowing down the shutter if I needed to a great depth of field. That is mainly because I photograph children and I’m also moving all the time (to catch them — haha), so I’d much prefer grain in an image over blur!

    Other people’s opinions are great to hear, so please continue to pipe in, Rob. I think slowing down the shutter (over increasing ISO) would be a better choice for those photographing subjects/objects that don’t move much and/or if you use a tripod, etc. Or if you just hate grain. 🙂

  • Moe

    I totally get this. What I don’t understand is What is a Stop. When someone says it is one or two stops overexposed. What does that mean? You could change the shutter, ISO or aperture to get a better exposure. Is this just a term left over from Film when ISO was fixed and you would change the Aperture one stop to get a better exposure or is it something you can measure now?

  • Prabin Prakash


  • Britney

    This is really cool thanks a lot, I am starting my own business soon and I am a First timer and i was nervous about the exposure. So i read this just before my photo shoot that i am doing today thanks 🙂

  • Simpyfield so perfectly, thank you!

  • elena

    I just recently started paying attention to all the settings and what they do in the past month, even though I’ve been shooting with a DSLR for over 3 years. The one thing I’ve been really stuck on is the ISO. /moonglasses/ is such a great way to describe it. The only question I’m left with, is when and why would you ever need an ISO setting that goes up to 16000??!? haha (:

  • Being fairly new to this blog, I found this article very helpful. In teaching my Entry to Digital Photography Class, I’m always looking for new and better ways to explain the Exposure Triangle.
    The analogy I’ve used that works well I call “filling the water glass”. You can fill a water glass (light) quickly by turning on the faucet on high; or slowly by letting the water trickle in (shutter speed). Regardless, the water glass will get filled -providing the right exposure. If it’s not filled all the way the picture will be under exposed. If it over flows, the picture will be over exposed.
    For ISO, I liken it to turning up the dial on your stereo -cranking it up will make the sensor more sensitive to light, turning it down will make it less sensitive to light. Of course, just like with your stereo, if you turn it up too loud it will begin to distort the sound (digital noise). I like your Moon Glasses analogy too! Hope you don’t mind if I use that one in my next class.

  • Amol Kale

    what’s a difference between exposure and aperture… please explain me..?

  • Maria R

    Great analogy, thanks! I think of ISO as a light switch. Use more if it’s dark and less if it’s too bright. Shutter speed – freeze motion use fast speed and to blur use slow speed. Aperture – comparing to the eye makes sense.

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