Click through to read more. Want to learn more about the Nikon Z9? Do you have a burning question you haven't seen answered anywhere else? Join us for a live Twitter Space on Thursday, November 11, and be part of the conversation. Click through for details. The four firmware updates bring improved autofocus performance in a number of different shooting modes, as well as support for Nikon's new FTZ II mount adapter and Nikkor Z mm F4 S lens.
Adrian Smith is back with another excellent slow-motion video of insects filmed with a high-speed Phantom camera. The original Tamron mm F2. Now Tamron is back with a second gen version that promises to be even better. Does it deliver on that claim? Chris and Jordan did a side-by-side comparison to find out. Check out their gallery of sample photos to judge critical image quality for yourself.
The lens will be a part of Panasonic's F1. Aptolux is a new company formed by videographers to create lighting solutions for videographers. Its first product is the Aptolux MP-1, a modular, transforming LED light that can be as compact as a lunchbox when not being used yet deliver bright, efficient light. Sony's latest a7-series model is the most capable yet, but also the most expensive.
We've been using Panasonic's new Lumix S 35mm F1. Panasonic has announced the Lumix S 35mm F1. Panasonic has released firmware version 1. The Hubble Space Telescope is in safe mode as engineers work to investigate what's wrong with the telescope's onboard instruments.
This is the second time the venerable telescope has faced extended downtime after being offline for a month earlier this year. Panasonic China has posted a pair of images to various Chinese social media sites that tease what appears to be a new lens launch. Gordon Laing is back at it again with another Retro Review.
In this episode, Laing goes back 25 years to provide an in-depth overview of Nikon's unique Coolpix camera, which was half compact camera, half PDA.
The adapter includes optics to help offset the crop factor of APS-C cameras. OM Digital Solutions — the company that's bought the Olympus imaging division — has just launched the M. Zuiko Digital ED 20mm F1. Click through for a closer look. Chris and Jordan tease-out the differences. After quickly selling out of its first batch back in , Lomography has announced that it's re-releasing its color-shifting LomoChrome Turquoise Film in 35mm, and format.
The search for understanding in the far reaches of the known universe is an expensive endeavor. Every 10 years, US astronomers and astrophysicists release a report outlining their goals and hopes for the next decade of space exploration.
The latest report has been released. This second-generation 50mm F1. Submit a News Tip! Reading mode: Light Dark. Login Register. Best cameras and lenses. Now reading: A visual history of Canon autofocus and how it works today 11 comments. Via: Shutterbug. Tags: video , autofocus , canon. View Comments Comments All Ola Forsslund "measure the discrepancies in light wavelengths" Is that how it works?
RUcrAZ Whoever wrote that it does an "excellent job explaining Tom Holly I was expecting to learn how they worked.. I'm glad they clarified that.
Adam2 A dumbed down, generic advertisement? Alex Efimoff I realized it was an ad when found no useful or interesting information in this video. Not to mention the video was posted by Canon itself. What do things like 'high precision' and 'dual-line zigzag arrangement' actually mean?
Number of points is self-explanatory. Geometry of points adds a layer of complexity, but both number and basic geometry are usually part of the top-line spec for an AF system e. Complex geometry includes things like dual-cross points and dual-line zig zag arrangements. More on that later. Globally, accuracy is how 'close to true' the AF system gets, and Canon doesn't offer any specifications for this characteristic.
Note that global accuracy is affected and hopefully, corrected by AF microadjustment. Locally, geometry affects accuracy, because a cross-type point has a better chance of achieving proper focus than a single-orientation point, since it samples features with different orientations. Precision is repeatability - if you take several shots of the same thing, how close will the focus of any one shot be to all the other shots?
Note that depth of focus is related to, but not the same as, depth of field, although the same factors influence both.
Overall sensitivity is how well the AF system performs in low light. The AF sensor is composed of multiple bit line sensors and associated amplifier circuitry - the more amplification within the limits of signal to noise , the less light needed to focus. AF sensitivity is specified as an EV range, and the lower the first number, the better. EV units are 'stops' so the 1D X can achieve AF in half as much light as the previous 1-series bodies. Sensitivity is used in another context as well, associated with lens aperture e.
Speed is another characteristic for which Canon offers no metrics, probably because there are too many variables. But better AF sensors and better processors result in faster AF performance. Coverage area is a very important factor - the broader the area of the frame where there are AF points, the more likely that an AF point will fall on your subject. More on this later. Of the above characteristics, number, sensitivity, speed, and coverage area are fairly straightforward. But geometry, accuracy, and precision are more complex, especially because the lens mounted to the camera will change the way in which the AF points operate in terms of geometry, accuracy, and precision.
A basic, single line AF point can detect contrast only in one dimension - the dimension 'opposite' to the orientation of the line. Remember that split prism in the manual focus SLR? The 'split' was horizontal, so you had to look for a vertical feature to focus on for the prism to be effective.
So, a horizontally-oriented line sensor will detect vertical lines like a flagpole or the side of a door frame , while a vertically-oriented line sensor will detect horizontal lines like a horizon or a boat on the water. There's some confusing terminology here - a "vertical line sensor" is the same as a "horizontally-sensitive line sensor" and vice versa.
A 'dual-line zig zag' arrangement found on a few points in some xxD bodies and the 7D, and on all the points of the 1D X means a line sensor that's actually two parallel lines instead of just a single line, and the pixels in those two lines are offset by half a pixel, meaning the point of maximum phase alignment can be more accurately determined because it will fall on a pixel in one line or the other, whereas with a single line it could fall between two pixels.
Generally, an aperture value is associated with an AF line sensor. In this case, though, a wider aperture simply means a wider baseline for the rangefinder system is required for that line to function. Note that these thresholds are not absolute - a lens with a narrower aperture than the threshold might still work, but at reduced effectiveness, accuracy, and speed.
Thus, Canon limits the functionality to the rated aperture for a given AF sensor. Find out more about AF operation modes. With either, the camera focuses using a single AF point, but if it is unsure then it uses another AF point to assist, or may switch to that point instead — either the next point horizontally and vertically, or the next point diagonally as well.
Both of these are effective with moving subjects, which are difficult to track with 1-point AF; Zone AF, Large Zone Vertical, or Large Zone Horizontal — uses auto selection AF within a larger area, optionally focusing on the nearest subject or using various criteria such as faces, subject motion and subject distance. Find out more about AF methods.
Find out more about AF configuration options. Eye Detection on or off. One is used when images are composed in the viewfinder, and the other is used in Live View or video mode when the image is composed on the screen on the back of the camera. When you're using the viewfinder in a DSLR, the main reflex mirror reflects light into the viewfinder.
A sub-mirror behind the main mirror reflects some light into a dedicated autofocus sensor. In Live View or video mode, the main mirror lifts up out of the optical path so that the imaging sensor receives light all the time, not just during the exposure. In this mode, the DSLR uses the imaging sensor to gather autofocusing data. Mirrorless cameras use only this system. The sensors are in the base of the camera. As the sub-mirror behind the camera's reflex mirror reflects light down to these sensors, this light is split by a small lens assembly to form two separate images.
One image is formed on the first line sensor, the other on the second line sensor. If there is no deviation between the two images seen by the sensors, the camera knows the lens is focused.
However, if the spacing of the two images is not correct, a signal is sent to the lens motor to bring the subject into sharp focus. DSLRs in Live View mode and mirrorless cameras apply a similar principle but using data from two points on the imaging sensor.
This works on the principle that the image is sharpest when there is greatest contrast between adjacent pixels. This system will typically adjust the focus rapidly back and forth a few times to determine the point of peak contrast. Each pixel on the Dual Pixel CMOS sensor has two independent photodiodes the parts of the sensor that record light intensity or brightness.
The camera's processor compares the signals from the two photodiodes, and if they match, it knows that this area of the image is in focus. If there is any deviation between them, it looks at pairs of photodiodes across a group of pixels, and can then calculate which direction the lens needs to be adjusted to achieve sharp focus, and how much focus adjustment is required. It also gives the camera a significant advantage for tracking a subject around the frame, because there are no gaps between the AF points.
It offers huge advantages for video, including smooth tracking of moving subjects and dazzling pull focus effects with touch screen control, and the technology is used in Canon's Cinema EOS professional cine cameras. Most EOS cameras offer two different autofocusing modes, and some offer three. Although the end result is that the lens automatically focuses, you'll get best results by setting the mode to suit the subject.
The focus is locked with the first pressure on the shutter button. One-shot AF is best if you don't know which mode to use — it's a good general-purpose setting to suit most subjects. In practice, you compose your subject in the viewfinder and half-press the shutter button. Among other things, this activates the autofocusing. The lens will focus on the subject, and then lock.
A green focus confirmation signal will appear in the viewfinder to tell you focus has been achieved, and the in-focus beeper will sound unless you have deactivated it. As long as you keep partial pressure on the shutter button, the focus will not change, even if you move the camera to recompose the shot. This gives a very quick and convenient method of achieving focus lock. If focus is not achieved, the AF point will turn orange.
In One-Shot AF mode, the camera will not let you fully depress the shutter button to fire it unless the subject is in focus. This means that if the camera is unable to focus the lens, you will not be able to take a picture. The camera calculates where the subject will be at the moment the shutter fires and focuses the lens accordingly.
It continually checks the focus and refocuses the lens each time the camera-to-subject distance changes, right up to the moment of exposure. But one potential problem is that AI Servo AF allows the shutter to be fired even if the subject is not in focus.
If the lens has not finished refocusing or has failed to find the focus, you will end up with an unsharp image. Since the system is a predictive one, it continually calculates the next position of the subject being tracked by comparing focus distance results as they are received. The algorithm ignores a reading if it is significantly different from what is expected based on other results.
This helps to reduce the lens jumping completely out of focus. The camera makes the decision. But when should you switch? The camera works that out. The camera detects movement by taking several AF readings as the shutter button is partially pressed. If the subject distance changes between readings, the system concludes that the subject must be moving. The variation between distances allows the camera to determine the speed of movement. If you mostly shoot landscapes and other static subjects, AI Focus AF could be a good default setting for your camera.
The odd times when you encounter a subject travelling at speed, you won't have to remember to change the AF mode. If you're photographing moving subjects, having the lens focus on the subject as you press the shutter button is not ideal. It does not take account of "shutter lag" — the very brief amount of time between pressing the button and the shutter actually opening.
During this time, the reflex mirror inside a DSLR has to swing up to allow light passing through the lens to reach the sensor at the back of the camera. Mirrorless cameras also suffer from shutter lag — when using mechanical shutter, the shutter mechanism has to close and then open again for the exposure. But let's take an average of ms and see how far a subject can move in this amount of time. In a tenth of a second ms , they will cover 0.
This is unlikely to have a major impact on the focus. This is 40 times the speed of the walker, so the distance covered in a tenth of a second will be more than 5m.
This could easily throw the image seriously out of focus. In its cameras, Canon overcomes this problem with predictive focusing. After making several readings in AI Servo AF mode, the camera is able to determine the speed and direction of travel of a moving subject. It can then build this information into the instructions passed to the lens, so that the lens focuses on the point where the subject will be as the shutter opens.
When AI Servo AF is set, the camera continuously records the position of the subject and predicts where it will be for the next frame, based on its motion so far. If the camera fails to detect the subject position in one recording period, the AI Servo AF algorithm will ignore the negative result and the next focus point is based on the previous accurate results. It will also ignore the results when the AF distance appears to jump greatly, so that it can continue to track a subject even if an obstacle passes between you and your subject more on this later.
Equally, if there is a sudden large jump in the focus distance, the camera will not drive the lens to the new distance directly. Instead it will gradually drive the lens focus, based on the previous successful focus distance. We've noted that mirrorless cameras use the imaging sensor for focusing, but DSLRs have a separate focusing sensor.
This sensor was positioned to focus the lens on a subject in the centre of the viewfinder image. However, there are many circumstances where the main subject is not in the centre of the frame, so since the EOS 10 in , EOS cameras have multiple focusing points.
A number of AF sensors are positioned across the image area, each taking a reading from a different part of the scene. The camera can analyse these readings and decide which focusing point to activate.
Alternatively, the photographer can select the point to use. But either way, the lens is focused using the information from the active point. Some of these points are made up of two line sensors that create a cross, which is sensitive to both horizontal and vertical detail.
Single line sensors have difficulty focusing, for example, on an unbroken pattern of vertical lines, because focusing requires them to detect changes in contrast in the vertical line they scan. Cross type AF points improve AF speed, accuracy and effectiveness in low light. Some points, often the central point, can function as dual-cross type AF points.
This increases the sensitivity and precision of focus. Some of the points behave differently depending upon the maximum aperture of the lens that's mounted see the diagram below. As a rule, lenses with larger maximum apertures get the best from the camera's AF system. Although having many AF points allows the subject to be targeted precisely, there are times when it's convenient to group the points to cover a wider area, making the subject easier to locate.
These methods vary depending upon whether you're shooting with a DSLR in viewfinder mode or in Live View mode, or if you're using a mirrorless EOS camera, but they function in a similar way. Using Single Point AF or 1-point AF method, the photographer can select a single AF point from all of those available for the camera to use for focusing. Conversely, in Automatic Selection, the camera selects from any of the AF points available to focus the subject.
This is useful when shooting past obstacles, such as when focusing on an animal lying in long grass. However, Spot AF is not recommended for fast moving subjects or in very low light conditions. When you're using either of these two options the non cross-type AF points will blink during AF point selection so that you are aware if the AF point you wish to use is a cross-type point or not.
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