What is Aperture and How Does It Impact Your Photography
Wikipedia defines aperture as “a hole or an opening through which light travels.” Where it gets a little confusing is the smaller the aperture the bigger the number (e.g. F/22) or the larger/wider the aperture the smaller the number (e.g. F/6.3). Now, maybe you are wondering what the ‘F’ stands for in this equation. It is basically a correlation to the adjusted size of the aperture.
image courtesy of www.Wikipedia.com; author: Mohylek
1) large aperture e.g F/6.3 2) small aperture e.g. F/20
The number on the side of your lens represents its widest aperture (e.g. F/1.8 above). As a general rule of thumb, whatever number that is times it by a multiple of four will give you the aperture that is going to produce your sharpest image. However, these results vary from lens to lens. The best way to truly test this is to take the same picture at different apertures and view the results on your computer. However, keep in mind these results may differ at different focal lengths if testing a zoom lens.
Understanding aperture as it relates to depth of field
In landscape photography, most photographers want clarity from foreground to background. Generally, that is what is referred to as a large depth of field or DOF. To help you achieve this effect, I find it helpful to think of your camera’s aperture setting as metaphor for your eye as it is actually called the iris. When your eyes are wide open you can definitely see better straight in front of you and see more information as well; but you can’t see clearly out of your peripheral vision, especially if you are looking down or up. Meanwhile, if you squint or close your eye a bit a greater percentage of what you are seeing comes into focus, but the effect still is not optimal and you can only use it selectively. No one likes to walk around with their eyes squinted all the time just to see better!
The same principal is applied when trying to focus on something right in front as well as an object in the distant background. Your eye simply cannot focus on both objects at once. So, what am I getting at? Putting this altogether, if you are shooting with a wide angle lens <35mm and trying to capture a big scene from nearest foreground subject to distant mountains and sky…a smaller aperture e.g. F/16 is probably better. And that’s where many burgeoning photographers start. That will provide you with a greater percentage of clarity although what you are actually focusing on won’t be quite as clear. Conversely, if your subject matter is a little further away and your focal plane (the angle at which you are shooting) is straight a larger aperture e.g. F/10 will be produce at clearer image of your subject matter while still allowing for excellent depth of field.
The best way to decide in the field on what aperture without calculating hyperfocal distance (the nearest distance at which objects become acceptably clear) is to take some test shots with each of your lenses at different apertures, carefully review the images on your computer, and make a determination for yourself, which you think looks the best. Or if you don’t want to do that just do a Google search on your particular lens and its sharpest aperture and I’m sure you can find some opinions.
Once you’ve determined your aperture preferences, I recommend starting with those aperture settings in the field and then review each image on your LCD, zoom all the way in, and especially scrutinize the corners of your image. If your corners are acceptably clear, then you have achieved an acceptable DOF, but if your corners are still too blurry you’ll either need to 1) make your aperture smaller (higher F-stop) or 2) manually focus and use photoshop to blend your images for max DOF.
Depth of Field Blending As It Relates to Aperture
The advanced method of blending images at different focal points to achieve maximum depth of field has gained popularity over the last few years with the continuous amounts of technological advancements, especially with editing software. In certain circumstances and depending on the type of lens, depth of field blending is almost necessary to achieve optimal results. There are certainly many ways of doing this. It would be out of the context and scope of this article to go into detail about the various technical editing aspects of this technique. I bring it up because I found for myself using a mid-range aperture between F/10 – F/14 makes the process much easier because the extended depth of field makes transitions look more ‘seamless’.
Depth of field blending was necessary for this image of the Grand Canyon where the camera was pointed slightly down. I used two images both shot at F/14 to achieve this effect.
One creative effect that is achieved almost exclusively by aperture usage is that of a sunstar or sunburst. Keep in mind this general rule of thumb…if you are trying to achieve this effect shoot at F/22. Other factors that influence sunstars are the lens you are using and the placement of the the sunstar in the composition. Let’s look at these two examples.
Captured with a Canon 16-35mm F/2.8 wide angle lens.
Captured with a Canon 28-70 F/2.8 lens at 50mm
As you can see, there is quite a difference is the style of the effect. Both images were shot at sunrise. The top image of Mesa Arch was captured just minutes after sunrise, while the other image captured near the Dallas Divide in Colorado was about 40 minutes after sunrise. Just something to keep in mind.
To summarize, understanding aperture and using it to enhance your photography is important for a variety of reasons. We hope this post was able to streamline the technicalities of it to allow the photographer to focus on his or her creative vision while in the field.