The Mystery of the Exposure Triangle Revealed – and no math!

A basic to understand for any photographer whether still using film or shooting with a digital camera is to understand the relationship of the three components of a good exposure that gets you a good picture. Over the next three Fridays we’ll discuss in depth each aspect of this relationship and how they interact. So let’s set some basic groundwork first.

Exposure is letting light hit the sensor or film to take a picture. It is taking the picture! A good exposure is the right amount of light to have a full range of tones in the photograph – not too light, not too dark with a full range of details. An Underexposed picture will be too dark, with no details in the shadows. An Overexposed picture will be too light – with no details in the highlight or bright areas. Here’s a quick example:

(notice the loss of detail in the underexposed and overexposed pictures!)

Our Exposure Triangle is this:

• Aperture: How big an opening there is in the lens to let light in. Also called f/stop.
• Shutter Speed: How long the shutter stays open; how long the camera lets light in.
• ISO: How sensitive the camera is to light. Adjust for really bright light or really dim light.

The most crucial thing to remember is this: just like a real triangle, the exposure triangle is interrelated – if you change one, you have to change the other two to compensate. So if I make my shutter speed higher (say to stop action) I will need to adjust my aperture and/or ISO in order to compensate. If I adjust my aperture to get shallow depth of field for a nice “bokeh” effect, I have to adjust my shutter speed and/or ISO to compensate. (Don’t worry – we’ll cover these in a lot more detail in the next 3 posts!)

So here’s a quick review:

• A good picture has to have the right exposure.
• Exposure is controlled by three
  settings – shutter speed, aperture or f/stop, and ISO.
• These three are interrelated – if you change one, you have to adjust the others to compensate.

Thanks for hanging in there – this is tricky stuff to learn! Next week we will talk about ISO – how sensitive the camera is to light.

Confused? Wanting more? Have a questions? Leave a comment and I will answer it here.

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