The first essential creative option is the aperture.
Your first structural control is the aperture, the size of which creates the amount of depth of field (the breadth of focus) your image receives. Get this wrong, choose the size of the aperture incorrectly and your light is corrupted, your image is blurry and your message lies unreadable. Yes, it’s that important.
The Aperture
The word aperture quite literally means hole. In photography, it refers to the hole in your lens through which light passes. The aperture can be made larger or smaller by changing the f/number in your camera. Smaller f/numbers represent larger holes, while larger f/numbers represent smaller holes.
Simply think of the f/number as a fraction. Smaller numbers mean bigger holes (more light), while larger numbers mean smaller holes (less light). For instance f/3.5 represents a much larger aperture (hole) than f/16.
Of Depth of Field and the Aperture
To see things more clearly, we sometimes squint our eyes. By narrowing our vision we cut the amount of light and get a sharper image. The same holds true in photography. Take away light by shrinking the aperture and you get more things in focus. Open the aperture, on the other hand, and you get less.
When you choose larger apertures (small f/numbers), you allow more light into the lens. More light in the photography world equals more blur, both behind and in front of your subject. Portrait photographers love larger apertures (small f/numbers) as they make it exceedingly easy to isolate a singular subject.
When you choose smaller apertures (larger f/numbers), you allow less light into the lens. Less light equals more depth of field. Landscape photographers (looking to get as much in focus as possible) are fans of smaller apertures (larger f/numbers).
Which f/number you choose (of course) is up to you. Simply visualize what you want, choose the appropriate aperture size and focus your lens (placing your depth of field over your target area). Keep in mind however that (as with any other art form) it will take time to master. For now, it’s simply important that you know where the control is, what it’s used for and how to change it.
Familiarization Assignment
- Switch your camera to manual control.
- Locate your aperture control dial (check your manual if necessary).
- Choose the smallest aperture your current lens affords (largest f/number).
- Choose the largest aperture your current lens affords (smallest f/number).
- Choose f/5.6
- Choose f/8
- Choose f/6
- Choose f/16
As you can see, it’s not difficult changing the aperture, a few clicks and and that’s all there is to it.
Understanding Reciprocity
Three of the six structural controls, the aperture, the shutter speed and the ISO setting, are reciprocal in nature. This means that a change to any one of these will have the exact same effect on the level of illumination in the image as the another. Making the aperture smaller by one setting (or click) for instance takes away as much light as a change of one setting (or click) from the shutter speed or ISO. This is quite useful when needing to make quick changes to the lighting of a scene.
Depth of Field Preview Button Exercise
A Slight Problem
Most DSLR cameras today use an automated aperture system that keeps the aperture wide open (no matter which f/number you have chosen) until the picture taken. This can prove troublesome when trying to judge depth of field, as the image seen through the viewfinder will not match what you’ll capture on the sensor. To see the actual depth of field, you’ll need to disengage the automated aperture system momentarily so that you can get a preview of the actual depth of field. Take a moment and look up the phrase depth of field preview in your camera manual. Hopefully the manufacturer provides a solution (since they are the ones who created the problem) and offers a depth of field preview button (or mode).
Note: If you own a mirrorless camera, you’ll want to read about your depth of field preview options, as well. They will be considerably different (in a good way).
Review
The word aperture means hole. This particular hole is found in your lens. Its primary purpose is to give you control over the depth of field found in your image. By changing the size of the aperture, you can increase or decrease the breadth of focus in your image. Simply choose the correct aperture (by changing the f/number in your camera), place your now expanded or contracted focus plane over your target (by focusing your lens) … and you’re well on your way to a completely in focus image.
Key elements:
- The aperture is a variable-sized hole found in the lens.
- Adjust it by changing the f/number in your camera (or on your lens).
- Smaller f/numbers represent larger holes.
- Larger f/numbers represent smaller holes.
- With more light (larger hole), you get less depth of field (bigger blur both in front of and behind your focus plane).
- With less light (smaller hole), you get more depth of field (your focus plane’s width increases).
- The f/number (aperture size) is your first creative choice … you never change it once picked.
Next: Essential Creative Option #2 – The Shutter Speed
This is post #3 of 16 of In Camera Magic: The 12 Essential Creative Options, a free online photography course for creating spectacular images right in the camera.