From the example of the sunset picture in installment #1 of this photography basics series, you have learned the importance of taking full control over the exposure on your camera.  Now, it’s time to dig into your camera and learn the three most basic tools available to you in controlling the exposure.

Those tools are shutter speed, aperture, and ISO.  After I explain what each one does, I’ll explain why we need three separate tools to control the brightness or darkness of the photo.


close up photo of an aperture in a camera lens

A small aperture in a camera lens.

The aperture is a small set of blades in the lens that controls how much light will enter the camera.  The blades create a octagonal shape that can be widened (we photogs call it shooting “wide open”), or closed down to a small hole.  Obviously, if you shoot with the aperture wide open, then more light is allowed into the camera than if the aperture is closed down to only allow a tiny hole of light to enter the camera.

So suppose you take a picture that is too bright.  How do you fix it?  Simply choose a smaller aperture.  Simple! Aperture sizes are measured by f-stops.  A high f-stop like f-22 means that the aperture hole is quite small, and a low f-stop like f/3.5 means that the aperture is wide open.

Let’s test your knowledge to make sure you have it down.  If you take a picture and it’s too dark at f/5.6, would you choose a lower f-stop number or a higher one?  Yep!  You’d choose a lower f-stop number, which opens up the aperture to let in more light. The size of the aperture controls more than the brightness or darkness of the picture, though.

The aperture also controls the depth-of-field.  Depth-of-field is how much of the picture is sharp, and how much is blurry.  If you want to take a picture of a person and have the background be blurry, you’d use shallow depth of field.  If you want to take a picture of a sweeping mountain vista, you’d want to use a small aperture size (high f-stop number) so that the entire scene is in sharp focus. If you, like me, are more of a visual learner, then I think this graphic will help solidify the information about aperture.  Take a minute and make sure you understand this info before moving on.

Graphic explanation of the aperture for photography basics learners


Shutter Speed

The shutter is a small “curtain” in the camera that quickly rolls over the image sensor (the digital version of film) and allows light to shine onto the imaging sensor for a fraction of a second. The longer the shutter allows light to shine onto the image sensor, the brighter the picture since more light is gathered.  A darker picture is produced when the shutter moves very quickly and only allows light to touch the imaging sensor for a tiny fraction of a second. The duration that the shutter allows light onto the image sensor is called the shutter speed, and is measured in fractions of a second.  So a shuttedr speed of 1/2 of a second will allow more light to touch the image sensor and will produce a brighter picture than a shutter speed of 1/200 of a second. So if you’re taking a picture an it is too dark, you could use a slower shutter speed to allow the camera to gather more light.

Example picture of motion blur caused by too slow of a shutter speed.

That’s me! Typing away on this article from my studio in Caldwell, Idaho.

Just as the aperture affects the exposure as well as the depth-of field, the shutter affects more than just the exposure.  The shutter speed is also principally responsible for controlling the amount of blur in a picture. If you think about it, it makes sense that the shutter speed controls how much blur is in the picture.

Imagine me sitting here at my computer desk waving to you (you don’t have to imagine very hard if you just look at the picture on the right).If you take a picture of me with a shutter speed of 1/30th of a second, then my hand will have moved in the time that the camera is recording the picture.  To get rid of the blur, you need to increase the shutter speed to around 1/320th of a second.  At this speed, my hand is still moving, but the camera takes the picture so fast that my hand travels only such a small distance that it is not noticeable in the picture.

Graphic explaining the effects of changing the shutter speed




The funny thing about ISO is that it is an acronym, but nobody really knows what it stands for.  It is always just called ISO even though it really stands for International Organization for Standardization.  Every once in a while, you’ll hear an older photographer pronounce it “I-so”, but almost everyone pronounces it “I.S.O.” The ISO controls the exposure by using software in the camera to make it extra sensitive to light.

A high ISO such as ISO 1,600 will produce a brighter picture than a lower ISO such as ISO 100. The drawback to increasing the ISO is that it makes the picture noisier.  Digital noise is apparent when a photo looks grainy. Have you ever taken a picture at night with your cell phone or your pocket camera, and noticed that it looks really grainy?  That is because the camera tried to compensate for the dark scene by choosing a high ISO, which causes more grain.

What constitutes a “high” ISO is constantly changing.  Camera companies are constantly improving the ability of cameras to use high ISOs without as much grain.  A few years ago, only the highest-end pro DSLR cameras could achieve 2,000 ISO, and now even entry-level DSLR cameras can shoot at this level.  Since each camera is different, you would do well to do a few tests with your camera to see how high of an ISO you can shoot at without making the image overly grainy.

Right now, you will commonly find new DSLRs that advertise expandable ISO ranges. To learn more about that, click here.

A graphic explanation of how ISO settings work in basic photography


Putting It All Together

A ram attempting to mate with a ewe bighorn sheep in Yellowstone.

Bighorn sheep in Yellowstone National Park

I know exactly what you’re thinking: “Why do I need three tools to control the exposure!?!?  Wouldn’t one suffice?”  The answer is no, and I’ll explain why with an example. In January 2012, I took a trip to my favorite place on the planet to take pictures–Yellowstone National Park.  My guide informed us that the bighorn sheep in the park were dying off very quickly due to whooping cough, so I worked hard that week to capture pictures of the last few sheep in that area of the park. Around 9AM on a cloudy day, I found a small group of bighorn sheep and started photographing them with a long 600mm lens.  The early hour and clouded sky made the situation quite dark for shooting.

The lens I was working with (which costs $11,000–don’t they know I’ve gotta send my kids to college?)… Anyway, it had a maximum aperture size of f/4.  So I set my aperture at f/4 to gather as much light as possible.  This also impacted the depth-of field to blur out the rocks behind the bighorn sheep. Next, I set my shutter speed.  I wanted to capture action in the photo, so I set my camera to 1/1000th of a second shutter speed.  I knew that this fast of a shutter speed would prevent any motion blur from the sheep running on the mountain side. Then, I took a picture.  WAAAY too dark!  I couldn’t compromise my shutter speed or aperture, so I knew I needed to use the third player in the exposure triangle–the ISO.

I played around with my ISO and found that if I increased it to ISO 640, it made the picture bright enough to take the picture without making it overly grainy. Yahtzee!  This combination of shutter speed, aperture, and ISO worked out perfectly.  Now can you see why you need to know how to shutter, aperture, AND ISO, and know how to set them independently on your camera?

In part 3 of the Photo Basics Series, I’m going to teach you how to set these on your camera.

Go to Page 3 of the Tutorial

  • Guruprasad

    Great article. Thanks for posting this.

  • Manju

    I had bought Sony a7 with Sony 28-70 lens. Started learning by self with trial and errors. I found it difficult to understand the terms such as Aperture, shutter speed, iso, etc. After going thru this article many of my doubts are clarified. Yesterday I bought Sony 70-200 f/4 lens !! Thanks a lot !!!

    • Gopi

      I bought Nikon D710 0 Nikon Nikkor 18-140 mm 1:3.5-5.6 lens and Nikon Speed light SB-910 . I am trying to learn more about this camera processing like shutter speed ISO aperture. Please give me some examples to learn and getting good pictures.

      Thank you


  • SPandey

    Very Very Useful and beautifully explained. Thanks a lot.

  • Joy Factor

    Wow! I just a bought a camera and reading the instructions on how to use each one of those tiny buttons is very tiring for me but thanks to you for doing an amazing job for making my life so easier! I am a mountain climber and love to take landscape pictures and will sure try this. Thank You!

  • Anna

    I always appreciate when someone teaches well. You explained it succinctly and clearly. Thank you!

  • howie b

    thanks for the refreshing read!

  • Lo

    By George… or By Jim… I think I am actually comprehending this Aperture, Shutter Speed and ISO thing finally. You are explaining it very well and the bighorn sheep example was excellent!! Excited for page 3 of the tutorial. PS I really hate the whole f/stop big number is smaller opening/larger number is smaller opening. Really who came up with that! Not logical for me but I will roll with it.

  • Daemon

    This is super helpful, much more understandable than other articles.

  • John Rowan

    This has helped me heaps thank you. Easy to read and understand, big thumbs up!!

  • ishaan

    hy !
    i bought hx400v sony ! but i m nt able to blur the backgroung !
    can u tell me how to focus ?

  • Khalil Hanna Hraimat

    Thank you so much for posting this article, really loved it and very useful, but still I have a question, do you intend to change the shutter, aperture, and ISO in specific order? If YES please explain.

    • Jeff Harmon


      I always want the ISO to be the smallest number it can be, so I set it at 100 to start with (unless I can tell from experience the lighting is too low then I will start with 400 or 800). Then I have to decide if my emphasis is stopping motion vs. the depth-of-field. If I want to stop motion I may use shutter priority mode so that I can se the shutter speed and let the camera figure out the aperture. If I want to control the depth-of-field (either making sure everything is in focus or only the subject is in focus and the background is blurry) then I will use aperture priority mode and let the camera set the shutter speed. It just depends what shot you are trying to create.

      Great question, I think I may do a Photo Taco episode on it!

      Jeff Harmon

      • Khalil Hanna Hraimat

        Thank you Jeff, I think this is you are totally right, instead to handle everything in Manual at once, sometimes when you in rush and you need this shot, you can’t make the precise decision unless you pick the suitable creative mode which suits the moment, as you said, if your interest is in getting the depth of field and focus, then you do this and let the camera do the rest, I’ll start adopt myself in using the creative modes more.

        Yes, I encourage you to do an episode about it, beginners like me will appreciate it too much :) Thanks again pal.