The Exposure Triangle

Film cameras, (for those of you who remember loading film into your camera, shooting a roll, sending it off to the LAB, waiting patiently for it to come back, then looking through the prints … and the prints that looked good and the prints that .. well, didn’t … but you still kept them all in that shoe box ..”because you paid for them” ) were actually fairly easy to  use. There really weren’t too many settings. The film was a particular “speed” (like 100 speed .. which is actually the ISO) and if you were really into it, you set the aperture and and shutter speed using the in-camera metering system and took the shot.

Digital cameras allow us to see each photograph as we shoot it. So no more bad pictures in a shoe box in the basement. But most are still using the camera’s automatic setting (it might be a green box on your camera’s dial). If this is you, you may still be getting lots of dark or really bright pictures, or blurry pictures or pictures where not everyone in the group is in focus.

For those who want to get a little bit more daring you can shoot using manual mode  (the letter M on your camera’s dial) and learn the simple rules of the exposure triangle. It all starts with asking yourself “Am I photographing the bird or the branch?”

The Exposure Triangle is :

  • Aperture  – How much the lens opens ( the smaller the aperture number the more light it lets in … but the shorter the depth of field .. meaning how much of the subject or group will be in focus)
  • Shutter Speed – How long the shutter is open ( the slower the shutter speed the more light it lets in but the bigger chance of a blurry picture if your subject were to move)
  • ISO – The “speed of the film” (the higher the ISO the more sensitive to light – or darkness depending how you look at it the camera will be)

You have to set one of these first and which you choose is typically determined by what you are photographing.

So “The bird or the branch”?   The bird might fly away but the branch will probably be fairly steady and this tells us where to start.  (to make this a little easier if the area you’re in is bright set the camera to ISO 100 and if the area is darker, set the ISO to 800).

OK, You’re focusing on this bird (which might fly away at any second) so you need to start with setting the shutter speed to a fast setting like 200/second.

The ISO is set,   the shutter speed is set, the  last thing you have to choose is the aperture setting.

The beauty of this is you just have to get the exposure to look the way you want it to look.  If you’re using live view (the screen on the back of the camera) just change the aperture setting until the picture is as bright as you want it. If you’re using the “in-camera meter” (this is the bar with little notches you see when you look through the view finder) you change the aperture setting until the arrow is above the dead center notch.


What if no matter where you set the aperture the little arrow won’t go above dead center on the meter!!   Well now we turn to our friend “ISO” again.  Is the picture on the live view too dark or is the meter stuck on the dark side ?  OK, set the ISO to a higher number (making the camera’s sensor more sensitive to light) .  Is the picture on the live view too bright or the meter stuck on the bright side ? OK, set the ISO to a lower number. When it looks great, push that shutter button !

And if you’re taking a picture of a flower ( something that won’t move ) you would (after setting the ISO to 100 or 800) set the aperture first – remember a small aperture number gives you a shallow depth of field so that only the flower will be in focus.  Then you set the shutter speed.


Why go to all this trouble when you can just set the camera on automatic and let the camera make all these settings for you?   Remember the bird or the branch ?  The bird could fly away .. the child playing soccer is running. Blurry pictures.

Using the exposure triangle in the camera’s manual mode allows us to set two of the settings and just change the third to make each picture look the way we want it.

You’ve just had the first lesson I teach in my one-on-one class at my studio in Walpole MA.   Just getting comfortable  with this basic way of taking pictures will make a huge difference in how your pictures will look.

Senior Picture © dan busler photography

Now I just have to get you to shoot raw (not JPEG), use a light meter , use a gray balance tool .. and correcting color , off camera flash .. and .. the list goes on I’m afraid.

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