When we take photos, we try to find the best balance of the three sides of the exposure triangle: Shutter Speed, Aperture and ISO. Depending on what we want in our photo, there are reasons  to choose one over the others, as being the most critical element.  Which leads to the question, “why can’t it be simple?”

If you’ve followed the first three articles, which covered the details of the three legs (ISO, aperture and shutter speed), you know the basics.  So now let’s pull it all together and get a jump-start in getting out of auto and using manual mode.

Review Of The Elements

Shutter Speed -(affects light and motion) – To freeze motion, we need a fast shutter speed (at least 1/125), again letting in less light. If we want to blur the motion, we let more light in, with a slower shutter speed.

 

Aperture – (affects light and depth of field) We set our aperture to create the depth of field we want.  Do I want everything in focus?  Do I want just their eye to be in focus?  The larger the depth of field I want, the less light that we let get to the sensor (bigger numbers), this requires me to either raise the ISO (more noise) or slow my shutter speed down (more blur).    So, to capture a fantastic sunset, or fireworks, I need a tripod, so I can use a slow shutter speed, higher aperture and an ISO setting as low as possible (this is limited by my camera’s sensor, every new generation of camera seems to have better low light capabilities).

 

ISO – (affects quality with noise or grain) It controls the sensitivity to light.  High ISO numbers help to get a photo in low levels of light.  But with increasing ISO, we risk more noise, or grain – our goal is to keep the ISO number as low as possible. That gives us the best chance for better quality.  Remember, higher ISO settings lead to more noise, and while some noise is acceptable, we want to avoid it whenever we can.  So, keep it as close to ISO 100 as you can.

Balancing The Exposure Triangle

This is the dance we have to do.  Move one element and re-balance the exposure by moving another one.  Here are some guidelines to get you started:

Sports – We need fast shutter speeds, balanced with a good depth of field and moderate noise.   So, pick your shutter speed for the effect, set your aperture for depth of field, and adjust the ISO to balance it all out. (Or set the ISO and balance with depth of field).

Landscape – EVERYONE says to shoot landscapes during the golden hour before/after sunrise/sunset.  Pick the aperture for a deep depth of field, set the ISO for  high quality (100), and use shutter speed to balance the others. (HINT: use a tripod to use slower shutter speeds (below 1/60 s) and avoid camera shake .  Of course any movement in the photo will create blur if we go too slow (wind, animals, people).

Low light photography – I set my ISO higher, pick my aperture for depth of field and dial in my shutter speed for balance.  If I can use a tripod, I can use a faster shutter and lower ISO.

These are all simple generalizations, but they give you the basic thought process you use to balance the exposure triangle.  Once you have a good exposure, you can choose to change the settings for effect. Remember, if I move my aperture by a stop in one direction, then I need to move either the ISO, or the shutter speed, a stop in the opposite.  If I do this, the exposure stays the same, but the depth of field, the noise, or the motion, are changed.

So in a landscape example (1/250 @ f11 and 400 ISO).  Moving from 1/250 of a second, to 1/500, cuts the amount of light in half, so I need to either change my ISO from 400 to 200, OR, I can change my aperture from f11 to f8.  Again, the exposure is the same, but I’ve stopped motion, shortened my depth of field and/or added some noise to the final image.

In the days of film, we picked our film speed (ISO) and could only adjust the shutter speed or the aperture to get our exposure.  If I couldn’t get the shot with ISO 400 (pretty easy film to find), I didn’t get the shot.  With modern digital cameras, we are able to capture things that were impossible in the past.

So, take some time, and play with this.  Try your hand at sports, or motion photography.  Try shooting fireworks or get up early and capture a sunrise.  As much of a challenge as it can be to learn these things, your ability to create fantastic photos will be greatly improved.

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Related Posts:

 

ISO

Shutter Speed

Aperture