Camera Buyer's Guide

Lesson 9 of 15

Autofocus

 

Camera Buyer's Guide

Lesson 9 of 15

Autofocus

 

Lesson Info

Autofocus

It's time to dive in to autofocus, not all cameras have autofocus but pretty much all of them do and knowing how it works and what to look for is important. So first up, for those of you in the Nikon and Canon camps or potential camps, one of the important things to look for is the focusing point options that they have. Now obviously, more focusing points is gonna give you more versatility when it comes to focusing and the trend over the last several years, actually through the entire age of autofocus over the last 20, 30 years has been more and more focusing points. The latest one from Nikon has 153 focusing points which makes it very, very good at tracking fast-moving subjects. Now, something to know about these cameras is that the SLRss, the Nikons and Canons are using something called Phase Detection Autofocus. What happens is light comes in to the camera, there is a mirror that we talked about for viewing your subject but the mirror is partially silvered and it allows some of the ...

light through to go to this phase detection sensor in the camera. So what happens is that there is a secondary mirror behind the first one which bounces some light down to the autofocusing sensor so that the camera can autofocus while you are looking through the camera. And having many options is a good thing to have. So the first thing you wanna look at is the number of focusing points. But the second thing you wanna look at is the coverage that you have. How much is covered from left to right, to top to bottom because the more coverage area that's the more places the subject can be while your camera focuses on that subject. Now this is mostly important, I have found in action photography. If your subjects are static, it's less important 'cause a lot of photographers will simply choose a single point in the middle. So on most of these cameras now, SLRs, and to some degree mirrorless, we'll address that more in just a moment, you're gonna be able to choose a single point of focus or you can choose all points where it will activate everything and will focus on whatever is closest to the camera. The medium and higher-end cameras will have the additional option of offering a group point. Now this may go by different names like Zone or Group Target and it allows you to have a group of points, which is less than all and more than one, so that you can track actions that's moving a little bit more erratically where a single point might not do it and where all points might be too many. And so I usually leave my camera on single point for simple and basic subjects and then I'll use group point when I'm focusing on action and I prefer not to use all points 'cause it's a little indiscriminate on what it picks up. I don't necessarily want the closest object to the camera. Now these focusing points in the Nikons and Canons in particular can get very complicated. And I'm just gonna give you one camera example and it's gonna get a little bit in depth here but you don't need to worry about memorizing this. It's just to know some of the different things that are going on in the camera. The cameras are using a phase detection sensor, which uses a couple sensors and they are looking for different types of line. For instance, horizontal lines, or vertical lines. And some of the sensor points are only good at picking up horizontal lines. In other cases, they're only good at picking up vertical lines and these maybe in different areas on the sensor and so the sensor has a variety of sensitivities depending on which point you've chosen at. Now, in this particular camera, the group in the middle are cross type points, which means they're good at vertical and horizontal. These are great ones. These are ones where you wanna be for really being able to track all sorts of different types of contrast 'cause that's what you're looking at for focusing. It's contrast, lines, things that the camera's sensor, the focusing sensor can grab on to. Now this particular system has an even more advanced system on the middle five points that are Dual-Cross and so it's looking for lines up, down, left, right, angle left, right as well, and so they're extremely sensitive in many, many different types of conditions. Now another factor, diving in a little bit deeper here, some sensors need a lens of 5.6 or faster in order for them to work properly. Other lenses will work with an f/4 lens or faster and this is where having a faster lens will help you focus better because the camera is more sensitive, that's more light coming in to the sensors that enable them to work better. And on this particular camera, the ones in the middle will work with a 5.6 sensor but if you have a lens that goes all the way down to 2.8, it'll have an extra layer of sensitivity and precision when it uses that. So when you use the highest-end glass, it's gonna be using the most precise system available. And so this is the autofocus system of what it's developed at over the last 30 years. And so when looking at the autofocusing system of the cameras that you're considering, you wanna consider the number of focusing points, the coverage area, left, right, up and down, the different types of focusing points and you're gonna have to dive pretty deep into the technical details and the people that should be diving deep in there are those that are really doing a lot of action photography. And then you also wanna look at AF point and lens compatibility because some lenses may not be able to be used with certain AF points if the lens doesn't allow in a lot of light. There's also an EV Focusing level reading that the cameras can focus down to a certain exposure value level and an EV of zero is considered pretty dark. A lot of cameras will go down to EV -2, some of them will go down to EV -3 and EV - and it's just a matter of how good that that camera can work under low-light conditions. Of course, lower the better, but you have to match it up with your needs as well. The way mirrorless cameras autofocus is very different than with SLRs. In this case, the cameras do not have that mirror with a secondary mirror. In this case, light come straight into the image sensor which you see on the back of the camera or in the EVF. And so what's happening, as the camera sensor sees the subject, it is trying to focus on it. And what it's doing is it's looking for strong contrast. On most all cameras, you're gonna get the option of having a box. And the beauty here is that you can have pretty much any size box they want you to have. And so, there are some cameras that give you a wide variety of very tiny, to very large boxes in order to focus. Another advantage with mirrorless is you don't need to worry about coverage because you can move the focusing box all the way around the frame, almost all the way to the edges in most cases. And so wherever you wanna focus, you can choose exactly where you want to focus. And this ends up being very, very precise for the user in the long run, and it's a great system to have. And so what it is doing once again is it's looking for contrast, it needs contrast, so a blank white wall is gonna prove very, very challenging for the cameras to focus on. Some of these cameras are using a hybrid system where they're using a bit of the technology from the SLRs along with this contrast detection system. And so when it's out of focus, normally it's just gonna use the image on the sensor but some of the cameras are using phase detection autofocus sensors that are extremely small and embedded right into the sensor, and these are very small and they're able to work around this with the pixel design and the cameras will have what's called a Hybrid Autofocus System and these tend to be better at focusing on fast-moving subjects. And so if you're using a mirrorless camera, and tracking action, look for the cameras that have a hybrid autofocus system built in to them. All right, some final thoughts on the focusing system especially when it comes to SLRs versus mirrorless cameras. The DSLRs are still considered faster in most all cases. There's a couple exceptions and the mirrorless is starting to make inroads into the speed that has been the domain of the DSLR user. Generally, they're better at tracking action especially in the lower price points and so if you wanna spend $ and get a camera that does pretty well at sports, right now that's the DSLR for sure. I love the mirrorless cameras 'cause you can focus anywhere you want in the frame, you can work with it on the LCD on the back of the camera or in the viewfinder, and it is incredibly accurate because it's taking information directly coming off the sensor and we also have new possibilities with face detection. So cameras can detect faces, it can even know who it is, how old that person is, if you've entered in that information into your camera's database. And it can track those faces as they move around the frame, and so it can be very good for certain types of action photography. So all of this is about where we focus in the frame. The other aspect to focusing is how we focus and there are two main options. The first option is Single Autofocus and this is where the camera focuses on a subject and then stops, and this is good for general photography because it allows you to recompose the subject into a pleasing composition. As an example, we want the person over on the left side of the frame in focus and we're using the center focusing point, we will move the frame over, we'll press halfway down on the shutter release, focus on our subject, the camera has then locking focus, you can recompose the camera and then press the remainder of the way down on the shutter release to take the final photo, and this is a technique that works for all sorts of subjects when you want one particular thing in focus but you are very particular about the final composition as well. And that is called Single Autofocus in most cameras. The other, very different type of focus is Continuous focus, and this is where the camera will track a subject and will continually adjust the focus as the subject gets closer to you. So if you do any sorts of sports photography, you're gonna probably wanna change your camera into continuous autofocusing as the first change over to this. This way, the camera can track and follow your subject as it's moving closer or further away from the camera so you can get a whole series of photos of that subject in focus. So, in summary, we have different focusing points and we have different focusing modes. Now, most of the time, when I'm doing basic photography, I would choose a single point and be in single autofocus. I would move the focus point or I would use the focus lock and recompose technique. I'll use continuous focusing in a group of points when I'm photographing action and mini cameras also have another option called Auto AF and this is where the camera will switch for you between single or continuous and most serious photographers do not like this mode because it's a little unpredictable which direction it's gonna go. It's kinda designed for people who don't know how their cameras totally work and will just make the decision for them. Once you know a little bit about photography, you'll want to make this decision yourself. All right. So, some final thoughts on the whole focusing system is use a single point if you wanna be the most accurate, that way you know it's exactly where it's focusing. You can use a group of points for action because it's little hard to keep a single point on a moving subject. We have single and continuous shooting and it basically depends on whether you're shooting a stationary subject or one that is moving. And so single for stationary and continuous for moving subjects.

Class Description

Buyer's guide will be your guide to figuring out the best digital camera for your needs.

Gear expert John Greengo dives into the major brands and lenses that are currently on the market.

John breaks down some of the more confusing aspects of mirrorless and DSLR's from focusing systems to sensor size; you'll get a better understanding of what the gear does so you can make an informed decision.

At the end of the class, John gives his recommendations for different types of photographers from the aspiring student to the filmmaker and everyone in between.

Reviews

Samantha Locadia
 

John is a great teacher, and I've learned allot in this lesson. I already had an idea what camera I want to buy next but happy to know it was also what he recommended (for my field). Really love his free classes by the way where he talks with other photographers and discusses photos of viewers. Awesome!

Michael And Dawn
 

John has a very good way of explaining things to make them both simple and complete. His makes great use of visual graphics in his explanations. I highly recommend any of his courses, the material presented is well thought out and flows very well.

Kevin Li
 

Amazing course. So much education provided in these free classes. I will definately be taking more. I am so glad I watched these before jumping in and buying a camera. This is a much watch for all people who are new to photography and are looking to buy a camera.