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What is Aperture Priority and When Should You Use It?
What is Aperture Priority and when should you use it for your photography? In today’s episode we’ll be talking about this topic, you’re listening to the Liam Photography Podcast, I’m your host Liam Douglas and this is Episode 191 for October 7th, 2021.
If you don’t know already Aperture Priority is a shooting mode that exists on pretty much all cameras. If you look at the mode dial on the top of your camera on the Canon cameras Aperture Priority is the mode indicated by the Av or on Nikon’s and Sony’s it’s the A mode. This mode is the “go to” mode for a LOT of photographers and they use it most all of the time unless,
- Time is an important part of making the image
- They are using studio flash
- Or they are in a shooting situation where full control over the camera is necessary.
But what is Aperture Priority?
Aperture Priority is a semi-auto mode on the camera where you as the photographer choose what Aperture you want to use because you want to achieve a certain look when it comes to your images. You want that look to be consistent from shot to shot regardless of what the lighting conditions are. What this means is in Aperture Priority mode, once you choose the Aperture or “F-stop” that the lens will use and the camera’s CPU decides the other factors of your shot and changes them automatically based on the lighting.
Let’s think of this as a “see-saw” like you had on the playground at elementary school when you were a kid. Once you set the Aperture of the lens, then the camera will change the shutter speed and ISO until your image is “level” again. I know the next thing you are probably asking is but what Aperture should I set? Well, this depends on how you want your images to look.
Setting the Aperture
Depending on whether you are shooting a landscape or a portrait or macro work, you will want to set the Aperture accordingly. Let’s say you are doing a portrait, well for portraits, we generally want the focus to be only on the person or couple in the shot. In this case we would use an aperture of say F/4 or maybe F/2.8 if your lens goes that wide. Keep in mind if it’s a couple, you want both of their faces to be sharp in focus so you probably want F/4 or maybe even F/5.6 where if it’s a single person or object than F/2.8 or maybe even wider will be fine. Remember, the Aperture of the lens means how wide the opening is and how much light it lets hit the sensor to make the image. So an Aperture of F/2.8 is going to be a fairly wide opening in the lens where an F/8 or F/16 is going to be a really small opening.
When you use a really wide opening you get what is called a shallow Depth of Field or small area where the focus is sharp and everything in the background is going to be blurry. On the inverse, if you use a small opening then EVERYTHING is the image is going to be in focus, such as the case when you want to shoot landscapes or architecture. So, if you are using a wide Aperture and letting more light onto the sensor you need a faster shutter speed to compensate and not “blow” out the image, where if you are using a narrower Aperture you want a slower shutter speed to allow more time to make the exposure.
When using Aperture Priority as a photographer you don’t need to strain your brain figuring out the ISO and the shutter speed because as I mentioned earlier, your camera’s CPU will work those settings out for you and you will get a perfect exposure, if you lens is capable of going wide enough to allow it. If you don’t have a really wide aperture lens, then the higher ISO and slower shutter speed might introduce “noise” into your final image. Noise is something we don’t want and if you remember from previous episodes where I talked about noise, noise is the digital “snow” that shows up in your images when you have your ISO set too high to compensate for the lack of a wide aperture.
What is Depth of Field or DoF?
To go into a little more detail of Depth of Field think of it this way. When you focus your lens to capture an image you are actually setting your lens to focus on everything a certain distance from your camera. Objects in that zone will be sharp and objects closer or further away will not be in sharp focus. So when you set a large aperture of say F/2.8 or F/1.4 you have what is called a shallow or narrow Depth of Field. In the image in the show notes you will see what I mean. In my sample image in the show notes of the Hummingbird feeder. The feeder is in sharp focus but the car, buildings and trees behind it are out of focus.
Next we’ll look at another example where we use a wide Depth of Field of say F/8 or even has much as F/16 or F/22. When you use a narrow aperture, then everything in the scene will appear in focus as in the photo in the show notes. In my sample image of the Georgia Guidestones I was using F/8 and you can see that not only are the guidestones in sharp focus but so is the sky, the clouds, the fence as well as the foreground. This is what’s known as a wide Depth of Field.
Depth of Field is something you can play with quite easily and experiment yourself at home. Using your kitchen table, line some small objects such as chess pieces of those little plastic green Army men figures you can pick up at a dollar store. Run them the length of the table, spaced about 1” apart. Now, stand at one end of the table with your camera and set your Aperture to say F/2.8 and look, focus on the figure near the center and snap the image. Next look at the image on your rear LCD or download it to your computer and look at in Lightroom or your favorite photo editor. See how only the center figure is in sharp focus, this is a shallow Depth of Field.
Now go back and take the same shot again but this time set your aperture to say F/22 and see what you get. This time all of the figures will be in sharp focus and in a wide Depth of Field. Remember when you are using a wide Depth of Field and a small Aperture you will see your ISO and shutter speed changed drastically. Now look at both images at the same time, can you see the difference?
A separate note on sharpness
Don’t fall into the trap of thinking that a smaller Aperture will give you sharp focus as that is not true. The wide Depth of Field will leave everything in focus, but the sharpest focus on most any lens is going to be in the middle of its Aperture range so around F/5.6 to F/8 is the focus “sweet spot”. Why is this, you might ask? Well, lenses are made to be sharpest at around F/8 and it can vary from maker to maker but if they concentrate on making the lens sharpest at the wider Aperture, the lenses would be even bigger and heavier than they already are and it would make them even more expensive. A lens’ sharpness degrades as you move to the extremes of say F/2.8 or F/22 and this is where professional grade lenses come in such as Canon’s L glass or Sony’s GM glass. These lenses have less degrading at the extreme ends and hence cost more money and are also larger and heavier.
When should I use Aperture Priority?
As I mentioned at the top of this episode Aperture Priority can be your “go to” mode for most all of your photography, especially if you are not comfortable with using full Manual mode on your shooting dial. This mode is extremely flexible and can handle the majority of shooting situations and gives you more control over your images than the fully automatic mode does. You can use Aperture Priority modes in every situation except.
- You can to introduce motion blur
- You need to freeze any action that is happening
- Working with studio flash, moonlights or speedlites
- Or you need Full control over your camera’s settings.
Wrapping it all up
Aperture Priority mode can be your single mode that you shoot with pretty much all the time. It allows you to dial in your Depth of Field by manually setting the Aperture you want to use and then the camera does the rest of the work for you. The “F-stops” are easier to use if you think of them in terms of Depth of Field. The larger the opening, and smaller the “F-stop” number, the least amount of items in the scene in focus and more out of focus and the wider your Depth of Field or smaller the opening in the lens, hence the larger the “F” number the more objects will be in focus to an extent. Don’t let those “F” number confuse you, follow this model and you’ll have an easier time, especially if you are new to photography.
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