The Exposure Triangle - Part Deux

Click here to visit The Exposure Triangle Part 1: Shutter Speed


So... knowing that we have three settings we can play with to generally adjust our exposure (how bright or dark a resulting photograph will be) and knowing that changing our shutter speed can capture the action of a rambunctious toddler, what can we now do to brighten up that image of the rambunctious toddler? Enter... APERTURE!! Dundada!! (Ok, I think that sounded way more dramatic in my head, but you get the idea ;)

Aperture is the second side of our famed Exposure Triangle and controls how much light enters the camera.

image credit: MU Photo

On every dSLR lens, there is an opening through which the light passes. On most (if not all) this opening can be made bigger or smaller depending on how much light you want to come pouring into your camera at one time. This is the aperture and is indicated by the F-number (i.e. - f1.8, f3.5, etc...).

Now, the somewhat confusing thing about aperture is that the smaller the F-number, the more light is being allowed into your camera and the larger the aperture is (so f1.8 is actually letting in MORE light than f3.5). The only way I've found to get that to stick in my head (other than repeated practice and more practice) is to think that the F-number indicates how restricted the opening is. f1.8 is less restricted and brighter than f3.5 which is more restricted (higher number) and therefore darker. Do you have any fabulous way of remembering this seemingly inverse relationship between f-number and brightness??

So, now we can brighten up that photo, by increasing the size of the opening on our lens and letting more light in (decreasing the f-number). Yippee!!



image credit: MU Photo

Now, as with all three of our "friends" in the Exposure Triangle, Little Miss Aperture does have some side effects. The main one of these is changing Depth of Field. What??! Depth of Field?? Depth of Field (often abbreviated as DoF) is how much depth in your image appears in focus. So, a larger depth of field means you might get both your subject and the mountains behind them and the grass in front of them in focus. A smaller DoF means that maybe just their eyes are in focus and everything else appears blurry. These days, there seems to be a push towards nice out-of-focus backgrounds with only the subject in focus. One way to get this is to open up your aperture to the widest possible setting (the smallest F-number) which will give you the shallowest DoF possible for that lens. A smaller F-number means a shallower DoF as well as letting in more light. Cool side-effect, eh? :)

image credit: MU Photo

So, now we've got two out of three sides of this mysterious triangle under control. Now what is that odd third side?? ISO??? Is that an alien language or something? That doesn't even look like English!

To find out more about this secretive third option to changing how bright or dark your photographs are, hang onto your hat for the third and final instalment of THE EXPOSURE TRIANGLE!! Dundada!! (again... much cooler and effective in my head, I'm sure... shows that I suck at sound effects :)

UPDATE:  Click here to visit The Exposure Triangle Part 3: ISO

Cheers!

lil' mama photog