Hannah Nielsen » Documentary Family Photographer Seattle Portland and Worldwide

Photography Basics: the Exposure Triangle

I had a request from the lovely Aria of Aria Couture for a run down on camera settings.  The next two posts are for those of you who have a good camera, but know you’re wasting your investment by not using the settings it allows you.  As always, if you have any questions please feel free to ask!  Let’s jump right in.

To understand your settings you need to first have a basic understanding of exposure.  I’ll start with that today and move on to camera settings tomorrow.  Exposure is determined by three things: ISO, shutter speed, aperture (otherwise known as the exposure triangle).  Here’s the most simple explanation of each I can come up with.

ISO – how sensitive the camera is to light.  If you’re in a darker room you can set your ISO high so that it’s sensitivity is higher and therefore less light is required to get your exposure correct.  In the bright outdoors, you can set your ISO low.  High might be somewhere around 1600 and low might be 100.  In Seattle I generally start at 200 and work from there since we get bright skies, but not full on sun most of the time.

Shutter speed – how quickly or slowly the shutter opens and closes (and therefore, how much light is let in).  The numbers correlate to seconds.  1/1600th of a second, 1/250th of a second, 1/60th of a second, etc.  The shutter is literally opening up for that amount of time.  So 1/1600th of a second is obviously a much faster shutter speed than 1/60th of a second.  Your shutter speed also determines how much motion is captured in your images.   If you leave your shutter open, the camera captures everything that happens while it is open.  In the first image below the shutter speed was very slow which is why you don’t see the girl walking by, but her movement.  A fast shutter speed freezes motion like in the second shot below.  If you don’t want to have any motion blur (or want to freeze motion) you’ll want to choose a shutter speed faster than 1/125th of a second as a general rule, but this is also determined by focal length and camera shake which we won’t get into today.  If you’re experiencing motion blur and don’t want it, use a faster shutter speed (this is how you get a shot of someone jumping when they’re in mid-air).  If you want the blur, slow it down.

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Aperture – how wide the iris of the lens opens (This works just like your eye!). When you go into a darker room, your iris gets wider, letting more light in so that you can see.  When you go out into the sun, it closes down so that you’re not blinded.)  Aperture also determines, in some part, your depth of field.  When you shoot wide open your depth of field is very narrow and everything in front of or behind your focus point will be out of focus.  For example, this image was shot wide open at 2.8.  The couple and everything on the same plane as them is in focus. You can see pretty clearly how the scaffolding behind them starts to fall more and more out of focus.  You can also see that closer to the camera on the right the scaffolding is out of focus as well.  The second image below was also shot wide open.  Notice how I’m closer to the couple, and in this case she is in my focus plane.  He is slightly in front of it, and therefore out of focus.  Everything behind them has blurred out. (I just love backgrounds like that!)  The smaller the aperture (f1.2, f2.8, etc.) the wider open you are shooting and therefore the narrower your depth of field.  The larger the number (f16, f22, etc.), the more closed down you are shooting and the broader your depth of field (as in the 3rd image below).   This confused me a lot at first because the numbers don’t seem to match the opening of the iris, but once I started mentally relating them to the depth of field it cleared right up.  The smaller the number, the smaller the depth of field.

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All three of these factors equally affect the exposure.  If you have a correct exposure (not too bright, not too dark) and you change one of these settings you will have to change another to get your exposure correct again.  Play with it.  Watch what your images look like when you change one thing or another or both or all three.  The best way to understand how ISO, shutter speed, and aperture affect your images is to try it!

Happy shooting!

 

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  • April 4, 2012 - 2:01 pm

    Aria Clements - “This confused me a lot at first because the numbers don’t seem to match the opening of the iris, but once I started mentally relating them to the depth of field it cleared right up.”

    THANK YOU!! This is what confused me most!

    I majorly screwed up some photos I took and didn’t realize it until the ensemble had been shipped. They came out washed out. How can you tell if the ISO is too high? What is the benefit to a lower ISO instead of a faster shutter speed? I think the aperture relates less to a good picture when it comes to a photo being too dark or overexposed, right? Is there some trick to figuring out ISO and shutter?

    You are awesome for this!!ReplyCancel

    • April 4, 2012 - 2:38 pm

      Hannah - If your ISO is too high it will become too sensitive to light and you’ll overexpose your image (too bright).

      Generally, you want to use the lowest ISO possible. The higher ISO you use, the more grain you will start to get (not really noticeable until higher ISOs in the 1600+ range depending on your camera…although when I shot with an XSi I experienced some grain as low as 800). However, when I say the lowest ISO possible, I mean the lowest you can shoot while still accomplishing what you want to. If you have to bump it to get the shutter speed or aperture you want or need, by all means!

      As a basic rule (like back in the film days when you just had to choose an ISO and stick with it for a whole roll) you want to set your ISO at 100 for a super bright (like full on sun) day, 200 for overcast, 400 for indoors but not dark and on up. I generally set my ISO and don’t really mess with it until there’s a drastic change in lighting, or I’m unable to get a shot I really want without tweaking it. I’d definitely suggest trying that when you first start messing with manual. (And yaaaay that you’re going to give manual some attention while you’re in Missouri! Would love to see some of your images!)

      Tweaking any of the three elements can lead to over or underexposure. If you’re aperture is too wide, in too bright of a lighting situation, with too high of an ISO, you will overexpose. The good news about it being the exposure triangle is that you can fix, say, your ISO, you can get the correct exposure without changing anything else. Or you can choose to keep your ISO and change something else to get the right exposure depending on what is important to you in that particular image. So maybe you’re already at a shutter speed of 1/125, and you really hate your background so you want a wide aperture, then you’d choose to change your ISO…but if the background is not so bad and you’re worried about hitting the point where you’d get grain on your camera, then you can close down your aperture instead. Does that make sense?

      Here’s a test you could do that might help explain it. Try to shoot the same exact shot (same place, same subject, same light) at each ISO…So start with 100, adjust your other settings until the little line is right in the middle on your meter when you look through the camera. Then bump your ISO to 200 and do it again. Write down your settings and see how they relate. Also, when you do this exercise, put the images on your computer and look at them. Make a mental note of where your camera starts showing you grain in your images.

      Did I just give you homework??? 🙂

      Let me know if there are more questions!ReplyCancel

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