Controlling Exposure: Shutter Speed & Aperture

As many introductory articles (on this site and beyond) explain, two key elements of controlling exposure (how light or dark a photo appears) are shutter speed and aperture. People far more knowledgeable than I have written good and comprehensive explanations of what these two things are and how to manage them - but I shall attempt to summarise what they say as succinctly as possible now:

“Generally, the wider the aperture, the faster the shutter speed”


“As the hole that lets the light in gets bigger, the amount of time that the light is actually let in for should get less”

Or even…

“As the f number goes down, so too should the s number” (remembering that the latter is often a fraction).

My esteemed colleagues might go on to say that if this rule-of-thumb is broken then you might risk over-exposure (say with wide aperture and slow shutter speed) or underexposure (narrow aperture and fast shutter speed). All of this, it should probably be mentioned, is a gross simplification of reality - there are lots of other things to consider, but let’s leave those for now. As a general “first lesson”, one could do worse than the above. It might help if we could see this in real life instead of just theorising about it, however:

Click on the PDF icon to open the Exposure Examples PDF file

The 49 images are all of the same thing, taken from the same position and with the same ambient light (which was quite low in this particular case). The point of the diagram is not to demonstrate precisely which shutter speed and aperture settings will give you the best exposure (as this will depend greatly on what you are photographing and where!), rather to give a quick visual demonstration of what the relationship between shutter speeds and apertures looks like. As we can see, where the balance between the two elements goes too far in the wrong direction, the images come out too light or too dark.