I can take a photo of my dog running around the yard easier than if it is jumping up right in front of me. What are focus points? If you remember the last lesson when I explained spot metering , you can use that concept to think about focus points. A camera might use dozens of focus points to bring a scene into focus, or you could select one focus point to focus on what you find important.
In some cases, you might use all of them or maybe just one. Many DSLR cameras will look at the metering of the scene to help it decide what to focus on. In a scene like this, the camera might realize that the subject is something bright against a dark background.
A smart camera will ignore the focus points in the dark areas and just use the ones in the bright areas. Even though you have all of the focus points activated, the camera may decide which ones to use.
The problem with using all of the focus points is that what you want in sharp focus and what the camera thinks should be in sharp focus can be two different things. If you have limited depth of field, then you might get the wings in focus, but the head and eyes will soft and possibly soft enough to ruin the photo. Using less focus points makes AF faster. I can cut that down to 21 and focus will be a little faster. I can cut further, down to 9 AF points and now the camera has much less to look at.
Focus points in the center of the frame are more accurate. In general, camera designers will put the more accurate cross-type AF sensors in the middle of the frame as that is usually where we are going to focus. Continuous focus works best with multiple AF points.
Even though I just said that less AF points are more accurate, you may need to use more if you are tracking a moving subject. If you try to follow a bird in flight with one AF point, you will possibly lose the bird and the camera will try to focus on the sky or trees behind it.
If you have several AF points active, then the chances of your camera tracking that bird become much higher. Not all AF points are cross-type. Remember when I mentioned that vertical lines can fool the autofocus? A cross-type sensor will work much better in this case, but only some of your AF points will be cross-type.
Of the 51 AF points, there are 15 cross-type sensors the 3 columns in the middle. On most cameras, you can move the 9 points around as a group. Another common technique is to focus on something, lock the focus and then recompose. With most cameras you can press the shutter half-way this locks the focus and usually the exposure as well and then recompose the scene and press the shutter button the rest of the way.
This works on stationary objects. Combine a single AF point with spot metering and you can make the camera work only of the part of the scene that you feel in important. This is also another way to help your composition. I would recommend that this is one thing every new photographer should practice. Try it with any stationary object and practice your composition.
Note: With many Zoom Zoom is a term used to describe magnification. A zoom lens will allow the photographer to change the magnification and viewing angle to frame a photo. Any increase focal length is considered zooming in, while any focal length shorter is considered zooming out. Here are the first steps that are part of the long journey to working towards ultimate sharp focus. Moving or Stationary? This is the first thing you need to consider.
If you or your subject are going to be moving you want to select continuous focus. You have to unless you plan on chasing the buffalo at an equal distance. If you are in the studio or shooting a still life subject, you might consider focusing and then turning the AF off. This lets you know that the focus will not change as you work on your scene. You can always check focus from time to time, but I do this a lot with Macro Macro is a term used to describe a type of photography involving small subjects.
Generally true macro is defined when you have the subject at a ratio on your film or sensor. Macro photography can be achieved via special lenses, attachments or other settings. How many AF Points? If you have a general scene like a landscape you can use more AF points and as you half-press the shutter, you will likely see many points light up to show which areas are in focus.
This is a good tool to use as you generally want a lot of the scene in focus, so use more points and let the camera do the work. If you have one small part of your scene that you want in focus, try the single point.
Some cameras even have face recognition modes that will look for faces in the scene and focus on them. If you have trouble using one AF point, try the next setting like 9 AF points. With fewer points active you need to pay closer attention to what the camera is seeing.
Learning to work with this while learning composition and other camera controls can be quite daunting, so try not to tackle too much in one photo session.
Try to experiment with a different aspect each time you go out shooting. Learn Your Controls. Taking the time to learn more about your camera is always a great idea.
Learning about how your particular camera focuses is a big step towards becoming a complete photographer. Collectively, the two methods are known as passive auto-focus. In contrast, laser auto-focus is a very different system. Instead, the phone will emit its own beam of infrared light towards the object. It calculates the time for the light to be reflected and is then able to calculate the distance to the object:. After the distance to the object has been determined, the lens is moved to the relevant position.
According to LG, the whole process only takes 0. This makes it a much quicker method than contrast-detection auto-focus. It uses the information to quickly focus the camera. According to LG, it only takes 0. It works in low-light conditions. Instead, it emits its own beam of light from which the distance to the object can then be determined. According to LG, laser auto-focus works best when the object is within 0.
The total range of effectiveness is around 5m beyond this, the phone will fall back to contrast-detection. It can sometimes be confused by reflections. For instance, if you try to take photos through a window, the laser beam could be reflected by the window.
This will give an incorrect measurement of distance the image will be focussed on the window rather than the object. Laser auto-focus is currently available only on high-end smartphones from LG. This will allow you to capture the full amount of detail. At present, most smartphones use a technique called contrast-detection to focus their images. In the past year, a number of alternative techniques have appeared on high-end smartphones for better auto-focus. Apple and Samsung are using phase-detection auto-focus whereas LG is using laser auto-focus.
Both methods are much faster than contrast-detection though they also both have their own downsides. For the best smartphones with a day money back guarantee, check out the giffgaff store. Written by abdulf. Blog home. How autofocus works When taking photos of an object, your camera phone will capture the light coming from it.
Fixed focus lenses In this example, only the blue ray of light is actually focussed. There are currently three different methods for performing auto-focus on a smartphone: Contrast-detection auto-focus. The following image illustrates how contrast detection auto-focus works: Contrast detection autofocus In contrast-detection auto-focus, your cameraphone will move the lens back and forth until it finds the point of maximum contrast.
Like contrast-detection, phase-detection auto-focus also works on analysing the light that comes into the lens. In low-light conditions, it can sometimes be difficult to analyse the image. In other words, an image that is in sharp focus will have high contrast pixels. If a digital photo is out of focus, then it will appear blurry. This is because the pixels on the image are not in sharp focus, therefore they have low pixel contrast.
Contrast-detection autofocus uses this information to figure out the correct point of focus. This light-dependent method achieves focus by means of trial and error. Low pixel contrast means the photo is out of focus.
To get the focus right, CDAF moves the focus motors to a position where the pixels are in sharp contrast.
The idea behind CDAF is that as the level of contrast between pixels increases, the more in focus an image becomes. As it does this, it compares contrast samples until it goes back to the point where the contrast between pixels was at the highest. You can actually see this in action when you take pictures on a phone camera that uses contrast-detection auto-focus.
CDAF does a decent job at passively focusing an image without the need for any additional hardware. However, because it physically has to move the lens in search for the best position where everything is in sharp contrast, CDAF is the slowest of all the auto-focus systems.
Contrast-detection autofocus works best for static images. If there are movements and action in the scene, the contrast information will change. Phase-detection auto-focus is a faster form of auto-focus than CDAF that goes by a few different names. This method of focusing relies more on software and algorithm than mechanically adjusting the lens position. With PDAF, a small amount roughly 10 percent or less of the pixels on a sensor are set aside and embedded with a phase detection photodiode a device on the image sensor that converts light into electric current.
Some of these pixels with phase-detection photodiodes receive light from the right side of the lens while others do so from the opposite side. This is similar to how we receive light separately through our left and right eye to create one image in our brains.
Using data from all the phase-detecting pixels spread across the sensor, the PDAF algorithm determines if the image is in focus. If the data of the light waves gathered from the photodiodes all match up, then the light profile is in phase and therefore the picture is in focus.
If the light waves are not in phase, the image will not be in focus. So, the light information captured by the photodiodes is used to determine the correct position of the lens in order to produce a sharp image. After everything is calculated, the focus motor then moves the lens to the right position for a crisp image.
This may sound like a lot but it all happens in a fraction of a second. This makes the PDAF system much faster than contrast-detection autofocus. It is this speed that makes it ideal even for moving action. Unfortunately, similar to CDAF, phase-detection autofocus relies on the light coming in through the lens. If the scene is too dark, then it may take longer for PDAF to analyse the scene and focus the image correctly.
How PDAF works on a typical smartphone camera sensor compared to dual-pixel auto-focus. Source: samsung. Introduced to smartphone cameras first by Samsung on the Galaxy S7, dual-pixel auto-focus takes what PDAF does and goes further with it.
This means that each and every pixel serves two purposes: to capture the image and to provide focus data. Unlike passive auto-focus, which relies on incoming light to work out the correct focus, active auto-focus relies on a dedicated internal device that calculates the distance between the camera and the subject.
Laser auto-focus is probably the most simple and straightforward system of auto-focus to understand. Popular some years ago with smartphone makers such as LG, laser auto-focus is an active AF system that uses infrared to determine focus. Where other auto-focus methods rely on incoming light to calculate and determine focus, laser auto-focus shoots out an invisible infrared laser beam that scans the scene.
This is not any different to how a time-of-flight ToF camera works on smartphones to create a depth map. Not to worry, though. When the laser fired from the phone hits an object, it is reflected back to the sensor.
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