Mastering the Exposure Triangle for Newbies

Mastering the Exposure Triangle for Newbies


When I first got my digital camera, words like Aperture, Shutter Speed and ISO were foreign to me, and it took me a couple of weeks of reading and studying a lot before the lightbulb turned on in my head. You might be feeling a little confused, and you may even feel like you will never get your camera out of Auto mode, because it’s just too hard to understand.


So, if you are unfamiliar with your camera, or just starting out, you might appreciate a little explanation of the basics. Sometimes reading about these things in slightly different words helps something new to click each time.

Introducing the Exposure Triangle: Aperture, Shutter Speed, and ISO

These three things work together to expose your picture perfectly, and after experimenting for a while, you may even find that you can use your knowledge of these three things to manipulate your picture for different effects.


The aperture or f-stop is how wide open your lens is. Imagine a hole: if it’s open just a teeny bit, there won’t be very much light coming through. If it’s a big hole, lots of light will come through. The tricky thing with aperture is that often confusing numbering system.

  • SMALL numbers (like f/1.8) = wide open aperture (large opening).
  • BIG numbers (like f/22) = small aperture (teeny opening).

That confused the heck out of me at first, but now it’s second nature. It will become second nature to you too, after some practice!

Another thing that can be affected by aperture is depth of field, or how much of your picture is in sharp focus. A wide open aperture (small number) will make less in focus, and a closed down aperture (big number) will make more in focus. Let’s look at some photos that demonstrate depth of field:


With the aperture set to f/3.5 on the left, you have a blurrier background (my favorite). Also notice that the shutter speed (1/640th) is fairly HIGH, we’ll get to this later.


A little bit smaller aperture (bigger number), makes the background come into focus a bit more, and the shutter speed is slowed down.


See what I mean? If you want to play around with Aperture, try putting your camera in Aperture Priority mode (A on Nikon, Av on Canon – if you have a different camera, check your manual).

Now, remember that all three parts work together? You probably started seeing how if you noticed the shutter speed changing with each of those different aperture values in the pictures above.


The shutter speed is how fast the shutter opens and closes. If the shutter is open longer, more light is let into the camera. If it opens and closes really fast, less light is let in.

If you have a wide open aperture, your shutter speed will need to be faster, because you’re already letting a lot of light in the lens opening. If your aperture is small, your shutter will need to move slower, so there is more time for light to get to the sensor.

If you want to freeze the action, or hand-hold your camera, then a faster shutter speed is needed. If you want to create blur, then you need a slower shutter speed. For example:


The vehicle in the photo on the left was driving past my house quite fast, but since I had the shutter speed set to 1/2000th of a second, it froze the action. It looks like the vehicle could be sitting still in the middle of the road.

The truck on the right is a blur going past, but everything else is still. 1/10th of a second was slow enough to blur the truck as it sped past. Notice the f-stop. Since the shutter was open for so long, the opening in the lens needed to be smaller to balance the exposure.

Try putting your camera in Shutter Priority mode (S on Nikon, Tv (time value) on Canon) to experiment with different shutter speeds. As you play with these different priority modes, notice what the camera chooses for the rest of your settings. The more you pay attention to these things, the more knowledge you’ll have to be able to set everything yourself in the future.

Okay, so now you’re probably asking, how does ISO fit into all of this?


The ISO is your camera’s mood. It can be all uptight and picky, or it can be easy-going and laid back. If you have the ISO set to a low number (100) your camera will want light, and plenty of it, because it’s going to take a smooth, crisp picture, and this requires perfect conditions. If you have your ISO set to a high number (3200) it can handle low light, because it’s not going to work as hard – a noisy (grainy) picture is good enough for Mr. High ISO.

So, how does this apply to your photography? Let’s say you wanted to take a picture in the evening, and you don’t want to use a flash. Just bump the ISO up, and it will allow you to have a faster shutter speed, or a smaller aperture (bigger number) and still accept the light conditions to expose correctly. Or, if you’re taking pictures at a sporting event, and you want to make sure you catch that action, but the light isn’t great, bump the ISO up. Or you may even want that moody grainy effect (it can be really cool)!

If you ever get frustrated because there’s just not enough light, and your pictures are blurry because the shutter speed isn’t fast enough, and you’re about to scream – just remember to bump the ISO. You could also leave this on Auto, but I usually don’t. My camera always seems to choose a higher ISO than I feel it needs. However, don’t forget to put it back down after you’re done. You don’t want to take a whole bunch of photos in the middle of the day at a 3200 ISO because you forgot to change it after your evening indoor party photos the night before.

Here’s a little demonstration:


ISO 3200

The photo above was taken in a very dimly lit room. Notice the digital noise?Notice the crispness of the photo below?


ISO 100



Well, that’s the exposure triangle in a nutshell. I hope this helped, especially if these three exposure factors have been confusing to you in the past. Please ask any questions in the comments, and I’ll answer them the best I can.

Read more from our Tips & Tutorials category

Melinda Smith was born to be a teacher. She teaches violin lessons and fitness classes, as well as photography classes and mentoring. She lives on a mini farm in Eastern Utah with her camera, husband, kids, chickens, horses, bunnies, dogs, and cats. Visit her at Melinda Smith Photography.

  • Jim Brito

    “My camera always seems to choose a higher ISO than I feel it needs.”
    It’s interesting that you say that. Just the other day I noticed while taking shots (Nikon) at the park mid day. I had my ISO set to 100 but auto ISO to 800. With camera set to Aperture priority, I noticed that some pictures were taken with an ISO somewhere between 640-800 with a ridiculously slow shutter speed. Why wouldn’t the camera “push” for lower ISO with increased shutter speed on such a bright day (but in shade at times)? Does Canon do this also? Have other photographers had this issue?
    I don’t remember if I switched to Shutter priority to see if ISO stayed “high”.

  • Interesting that you have had similar experiences with your camera choosing a high ISO. Glad to know it’s not just me!

  • Anne Mueller

    My Nikon D7100 did the same thing until I turned off the ISO sensitivity and set it manually for the conditions I’m shooting in. I like to shoot Aperture preferred and it always wanted to jump the ISO up to a ridiculous setting. It made my shots really noisy.

  • Bob Bevan Smith

    Whilst I agree that ISO affects the quality of the result, I think that a better way of thinking of it is to think that the camera is working harder under the low light conditions. It is a matter of Tone, rather than Mood. What it is doing is amplifying the electronic signal from the sensor, akin to a band using microphones to amplify their voices. Inevitably, the sound from the amplifier does not give exactly the same tone as if they had been singing naturally. The harder the amplifier works, the more distorted the sound.

  • Good analogy. Thanks for sharing!

  • MadDogMorgan

    You could have also just set a max ISO that you were comfortable with using in the settings for auto ISO

  • JvW

    Remember the advice to keep your shutter speed faster than 1/focal length in order to avoid camera shake? Canon, and I assume Nikon too, attempts to do that when you use auto-ISO in aperture priority.

    For example, if you’re using a 100mm lens, the program will attempt to keep the shutter speed faster than 1/100th (or 1/125) of a second. It will raise ISO as necessary to the maximum before dropping shutter speed below 1/125.

    That may be why you can see unexpectedly high ISO values.

  • In my experience, this wasn’t the case. The camera would choose a high ISO and the shutter speed would be very high, not even close to the 1/focal length “rule”. Maybe it would be the case in some cameras though. 🙂 Thank you for your comment!

  • You could do that, but maybe you’d set your max ISO to 800, and your camera would choose that on a sunny day, when 100 or 200 would be much better. For me, I still prefer to set my own ISO instead of letting my camera decide that. It’s pretty quick to set it at the beginning of a shoot, and most of the time can be left for the entire session. 🙂

  • MadDogMorgan

    I think people get a bit wound up about ISO, I generally shoot live performance/concert photography and regularly shoot at 6400 and above. Whatever is needed. We recently conducted an interesting experiment where the same photos at ISO100, ISO 800 and ISO 1600 were printed at 20 x 30 inches and viewed by over 100 working photographers at a distance of three feet. They were then surveyed and asked to rate the images and see if they could accurately identify the high ISO vs low ISO etc. Not one managed to correctly identify any of the images

  • I think you’re right, if you have a fairly good camera body. Some of the entry-level DSLRs have very obvious noise once you get up to an ISO of 800.

  • Aviv

    is there like a starting point of the triangle? like 1/160 f/11 iso 200? is it one to one change? like if i need to change one number up on the Shutter, do i need to change one number down on the Aperture? please explain

  • Great questions, Aviv. There’s not necessarily a starting point, because every single situation is going to have different lighting, and the combinations are endless too… for example, you might want to have the aperture closed down small so everything is in focus, or your goal may be to have the aperture wide open to blur the background. You could achieve either of those things in the same lighting situation, but the numbers would look very different, even if you exposed them both correctly. The small aperture would require the shutter speed to be a lot slower, and possibly the ISO to be higher. The large aperture would require the shutter speed to be faster, and a lower ISO.

    If you start at perfectly exposed, and want to move one of the numbers on one point of the triangle, you would need to compensate for that by moving one of the other numbers to balance it out. So yes, you are correct. If you moved your shutter speed one stop faster, you would need to either make your aperture one stop larger (smaller number) or you would need to move your ISO one stop higher. In the example of the flowers above, you can see how every time the aperture got smaller (bigger number), the shutter speed got slower.

    I do have a “starting point” when I start shooting each time. This may be different for other photographers, but this is the order that works for me. I choose my ISO first. If it’s a sunny day, I know that 100-200 ISO will work great. If it’s light, but a bit overcast, I’ll set it at 400. If I’m indoors, I’ll start at 800, etc. Occasionally I need to change this in the middle of a session, but most of the time I can leave the ISO where I started. Once I determine the ISO, I set the aperture for the effect that I want. If I’m photographing one person and I want the background blurred, I might start at f/2. Then once I’ve set that, I just set the shutter speed so everything is exposed correctly. I will move the aperture around multiple times during a session, and then just adjust the shutter speed accordingly.

    Hopefully that sheds some light for you. Let me know if you have more questions!

  • cody schlag


  • cody schlag

    my name jeff

  • Hey Melinda,

    Thanks for your words here, regarding the vehicle photos:

    “Since the shutter was open for so long, the opening in the lens needed to be smaller to balance the exposure.”

    That now makes so much sense – to balance the exposure!

  • Thank you for your comment!

  • Johan Bauwens

    Iso shouldn’t be in the exposure triangle, but the amount of light should be in ! Iso isn’t a physical aspect, but something internal (electronics) in the camera. Off course your Iso determines how ‘bright’ your picture is but it’s not the same

  • Daniel Buckenmyer

    Simply put, the triangle is a window, with a curtain and tint on it. The size of the window is the aperture, expressed in a fraction. 1/1.4 is a larger fraction than 1/2 or 1/8 or 1/32. Thus, f/1.4 is larger than f/2 or f/8 or f/32. Just think of the f stop as a 1/ and you will get it quick. The bigger the window, them more light that will come in, all other things held the same. With shutter speed, think that the curtain can open very fast, or very slow. 1/2 of a second is slower than 1/125th of second, so opening the curtain for a half a second gives more light than opening it open for just 1/125th of a second. ISO is how dark or light the tint on the window is. ISO used to be ASA. ISO 100 is heavy tint, which lets less light in than ISO 800, which lets in much more light. But remember that too much light makes it hard to see and you have to squint (smaller window) and you don’t want to open your eyes too long, otherwise it blinds you (shutter speed). Simple. Nice article.

  • Thanks for your comment! Great analogies!

  • RamKumar GK

    Hi Melinda, I just need to clarify that you posted above exposure triangle picture having exposure compensation (-2, to ,+2 ). My question is need to concentrate on this too(exposure compensation)?

  • Daisy May

    Hi I Melinda, I can’t thank you enough for this article! Over the years I have attended a one-to-one class, college classes for mature students, and I have read many books and articles on the Internet, but all the information went into my brain and was promptly shredded! An hour with your article and a pen and paper and it has all become so clear. I now can’t wait to get started. Thank you soooo much.

  • What a wonderful comment! You’re so welcome, and you’ve made my day! I’m glad I could explain it in a way that makes sense to you!

  • Beverly Johnston

    I like this idea.

  • David Jackson

    Exposure compensation is more of a fix for exposures that can’t be fixed by adjusting one of the other variables. If you’ve metered, set your aperture and ISO properly, and can’t make the shutter speed any slower, then you have to use exposure compensation to adjust the exposure level. It doesn’t always solve the problem, however.

  • papajon0s1

    I know this post is years old now but still as an amateur photographer, I am one of those people that needs to keep hearing the basics over and over since I am not doing this full time (which would be awesome!). But thanks for this, very helpful!

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