Saturday, September 14, 2013

What an Aperture of F/1.8 Can Do for You

What an Aperture of F/1.8 Can Do for You | Boost Your Photography

The first article in this series on aperture is called Aperture and the F/Stop Conundrum. When I was first starting out in photography, I found it much easier to wrap my head around aperture by thinking about what each aperture category could do for me than in trying to parse out all of the values and variables and terminology. So I wanted to organize this series of posts around three divisions of the aperture range and the benefits and limitations of each. This post will focus specifically on the wide-open end of the aperture spectrum, in the range of f/1.2 – f/5.6. The next two posts in this series will cover the narrow-end of the aperture spectrum, in the range of f/18 – f/22, and then the middle of the aperture spectrum, in the range of f/8 – f/11.

These bullet points summarize the main points about the two opposite ends of the spectrum:
  • F/1.8: A larger aperture value (larger fraction) = a wider opening = more light coming in = shallower depth of field (much less in focus) and a faster relative shutter speed
  • F/22: A small aperture value (smaller fraction) = a narrower opening = less light coming in = a wider depth of field (much more in focus) and a slower relative shutter speed
Necklace Bokeh by Archaeofrog on Flickr, shot at f/1.8

The wide-open end of the aperture spectrum is fantastic aperture for artsy photographs with blurry backgrounds or stunning bokeh (those out-of-focus dots of light and color). These are easiest to accomplish at the wider of the wide apertures, such as f/1.8. Not every lens is able to reach an aperture of f/1.8 or wider, however.

This photograph was taken at f/5, but the blur is still significant as the background trees are far away.

The widest aperture available on a given lens is often included in the name of the lens itself. If you have only a kit lens, then the widest aperture you have may be somewhere between f/3.5 and f/5.6. For many zoom lenses, the widest aperture you can get varies depending on whether you are using the wider or narrower end of the zooming capabilities of the lens. The kit lens that came with my Canon T1i, a EF-S 18-55 mm f/3.5 – f/5.6, means that it has a maximum wide aperture of f/3.5 when taking a picture at 18 mm but that the maximum wide aperture at 55 mm is only f/5.6. While it is still possible to achieve some of the neat effects, blurry backgrounds, and fancy bokeh at these values with a kit lens, your ability to do so increases tremendously with an even wider aperture.

This comparison of changing aperture is from the article Remember the Background and Move Your Feet!

This image offers a comparison of three aperture values on the wider-end of the spectrum. The wider the aperture value, the less of the image is within focus, and the easier it is to achieve a blurry background and bokeh. While the furthest back leaves are out-of-focus in all three images, by the time you reach the right-hand image and an aperture of f/1.8, only the two front leaves are left in focus.

If you currently have only the lens or lenses that came with your camera, and you really want to make a big difference in your photography and have a little to spend, then I highly recommend purchasing a 50 mm f/1.8 lens for your camera. (Read more in Yes, You Need a 50mm Lens.) Both Canon and Nikon make versions for their cameras that are around $100-120 USD. Considering most lens run into the multiple hundreds to thousands of dollars, this is a great starter lens for moving beyond your initial kit lens or lenses. A 50 mm prime lens is also a great tool for macro photography: read more in Cheap and Easy Macro: comparisons and recommendations.

What You Can Do with a Wide Aperture

Wide aperture lenses are prized for their ability to render backgrounds blurry and throw everything but a narrow plane of the photograph out of focus.

Autumn Leaves and Autumn Light by Archaeofrog on Flickr

This photograph, taken at f/2.2, shows how extremely thin the plane of focus (the depth of field) can become at close range. Large sections of both the foreground and the background are out of focus, and only the leaves and grass immediately within the middle are in focus. The slightly pentagonal nature of the bokeh (the blurry light shapes) is the result of the f/2.2 aperture. Had I used f/1.8, the widest aperture on this lens, the bokeh would be perfect circles. As the blades within the lens close down at each narrower aperture, they create a smaller and smaller pentagon. (This particular lens, the Canon 50 mm f/1.8 has five blades inside that control the aperture. Other lenses can have different numbers and would render different polygons.)

Since wider apertures allows in more light, they are also good apertures to choose in low-light situations. They allow you to capture more light at the same shutter speed or to use a faster shutter speed to capture the light you need. This is also useful if you are hand-holding your camera and need a faster shutter to avoid visible camera shake. (The rough rule of thumb is that you can hand-hold a lens for 1 divided by the length of the lens seconds. So 1/50 th of a second for a 50 mm lens or 1/250 th of a second for a 250 mm lens.)

Madison Area Milky Way by Archaeofrog on Flickr

Star photography benefits from a wide aperture as you want to capture as much light as possible. This photograph of the Milky Way was taken at 18 mm, f/3.5 (the widest available for this lens, the Tamron 18-270 mm), and the highest ISO on my camera. The high ISO makes for an extremely 'noisy' image but was necessary to try and gather as much light as possible during the 30-second exposure.

Portrait of my Grandmother by Archaeofrog on Flickr

Apertures on the wider end (like f/2.2 to 3.5) are also common in portrait photography. The narrower depth of field throws the background out of focus and helps separate the in-focus subject from the background. This portrait of my grandmother was taken at 50 mm, f/5.6, ISO 100, for 1/250 th of a second. Because of the wider aperture, the background trees are rendered as a pleasing blur of colors, and the crisp focus draws your attention to her face and hands, rather than the background.

Warmth by Archaeofrog on Flickr

Be careful when using f/1.8 with portraits however, as a close-up shot with a narrow depth of focus can result in an out-of-focus nose on the front of the in-focus eyes on a face! In this self-portrait, I wanted to use the narrow depth of field provided by f/1.8 to keep the focus and attention on the hands and the coffee cup. While it is clear that my face, necklace, etc. are falling out of focus, it achieved the look I wanted. When you are trying to capture a flattering portrait with the person as your focus, however, you want to be sure the whole of the face stays in focus.

Summary of Wide Apertures like F/1.8

The wider end of the aperture spectrum, roughly f/1.2 to f/5.6, is great for capturing a lot of light and rendering backgrounds blurry or full of bokeh. The wide-open apertures should be your go-to values for low night or night photography as well as flattering portraits. The narrow depth of field also works well for more abstract or artistic photographs. Spend some time exploring these apertures to see what effects work best for you.

Prairie Grasses by Archaeofrog on Flickr

Have you read up on Aperture and the F/Stop Conundrum? The next article in this series covers What an Aperture of F/22 Can Do for You, and the last article explains the Middle Range of Apertures: F/8-11.

Want more posts geared toward beginners? Click 'For Beginners' up at the top or try the rest of our series, Camera Settings and Strategies:

Want to learn more? Boost Your Photography: Learn Your DSLR is now available from Amazon. Get the most out of your camera with practical advice about the technical and creative aspects of DSLR photography that will have you taking beautiful pictures right away.
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