Time when we were buying SLR and digital SLR cameras for capturing various moments in our lives is gone. Now, those special moments are captured right from within your smartphones. Most of these smartphones have evolved to the point that it is right to say the best camera in the world is the one in your hands.
The time of puny 1 MP and 3 MP cameras is gone, and now it is time for 8 MP, 12 MP, 13 MP, or 41 MP cameras among smartphones. In this article, let’s look at the major technologies used in the cameras of our favorite smartphones.
According to research firm NPD’s statistics, in 2011, over 27 percent of the photos were taken by smartphone cameras. Also, this zest for camera phones is negatively affecting the point-and-shoot camera market.
The Basic Technology
Digital cameras have these—a lens, an image sensor technology, and the image signal processor. When you are taking videos with these digital cameras, one additional component called video encoder also comes into play. Here is a basic diagram showing what is happening in a smartphone camera.
As you can see there is communication between the CMOS sensor and the ISP to better interpret the scene captured with the lens. The sensor and the ISP may reverse-communicate to make the image better, as represented by the double arrows. During video-capture, this is how the video encoder comes into play.
Within smartphone cameras, we use the Complementary Metal-Oxide Semiconductor (CMOS) technology for the sensor. In other high-end digital cameras, the sensor uses a different technology known as CCD (Charge-Coupled Device). Both these technologies are identical in that they convert light into electric signals (similar to the solar cells).
CCD is more of a traditional kind of image sensor. It has a capacitor array that captures each pixel in the image, and the data is converted into an electric charge. These charges are then transferred through a shift register and converted into a voltage sequence that can be stored as a digital image.
|A representation of progressive scan in displays
CCD is an analog device, and it captures more natural images than the CMOS technology does. While in CCD, the entire image is converted into one sequence of voltage, within CMOS, each pixel has its own circuitry to create its own voltage sequence.
In essence, CCD captures the image in one shot, while CMOS captures it in sort of a scan, either vertically or horizontally (just like progressive scan). Hence, the CMOS sensor doesn’t get the entire image in a single instance.
I will not go into the details of these technologies.
The basic difference between CCD and CMOS is that CMOS uses much less power than CCD. This makes it perfect for handheld devices.
However, CMOS suffers from an issue known as ‘rolling shutter effect’, since it doesn’t take a picture in a single instance, but rather in a scan. When a CMOS sensor interprets a moving object, the image gets skewed. This is caused by the kind of shutter it uses—either global or rolling. If it uses the global shutter, the sensor won’t cause this issue. CCD sensors exclusively use global shutter and hence they are not affected by this issue. CMOS sensors commonly use the rolling shutter that causes the effect.
Your smartphone cannot house a larger CCD sensor as there are quite a few limitations, such as cost, materials used, the conditions in which the smartphone is used, etc. Hence, a CMOS sensor is usually regarded to be the best for tiny smartphone cameras. However, there have been CCD cameras on phones, such as this Sharp Aquos 933SH.
The Megapixel Myth
|HTC Titan II used 16 MP camera
During the last two years or so, smartphone manufacturers have been on a rat race to build cameras with the highest megapixel count. They simply upgraded the cameras up until they hit 16 megapixels.
That was supposed to be the limit, but then Nokia came up with its PureView 808 smartphone with a whopping 41 megapixel camera.
|Nokia PureView 808 with 41 MP image sensor
Let’s analyze why megapixel count after a certain limit does not represent image quality.
The number of megapixels on your phone’s camera represents the actual size of the image. For instance, Titan II’s 16 MP sensor can print an image at the size of 23.2×17.4 inches. And taking it further, the Nokia PureView 808’s camera (with 38 MP of effective pixels) will make an image of the size 35.76×26.84 inches or about 3×2 feet in size. This calculation is considering the 200 dpi resolution of a printer. If you consider an LCD screen of about 100 ppi resolution, the size will go up to twice as much.
Imagine how much disk space a large image would take. It will be much larger than the regular 8 MP image. This is the reason why Nokia PureView 808’s camera by default shoots images only at 5MP. What a waste of pixels! With your smartphone’s camera, you absolutely don’t need to create images of huge sizes. An 8 MP or a 10 MP camera can provide you with exactly what you want.
By the end of 2012, people as well as smartphone manufacturers started realizing that this industry talk about megapixels is quite a bit unnecessary. That has caused HTC to come up with HTC One smartphone that is barely 4 MP, but uses a different technology known as UltraPixel to capture more light through those pixels.
The size and quality of the camera’s lens is another factor that determines the image quality. A large diameter lens can produce much better images. With this in mind, Nokia has gone with Carl Zeiss optics for most of its smartphones. Carl Zeiss is a leading German manufacturer of lenses for various DSLR film cameras. Their optics finds uses in various industrial applications in metrology, medical technology, microscopy, etc.
Use of Carl Zeiss’s high quality optics has clearly increased the quality of images captured by Nokia smartphones. LG Optimus G also has a larger camera lens that makes its images much better.
If the camera is naturally capable of optical zoom, that is another aspect that will improve the quality of the image. An example is the Samsung Galaxy Camera that has a smartphone at the back.
This particular device has a 16 MP camera and 21x optical zoom (look at the size of that camera housing) and uses a BSI CMOS sensor. BSI is for Backside Illumination. This is a technique used to increase the amount of light captured, and thereby improve the low-light photographs.
Trademarked Camera Technologies
Now, we will take a look at the current technologies that we hear about in popular smartphone cameras. Some of these technologies are Nokia Lumia 920 smartphone’s PureView technology and Optical Image Stabilization (OIS), HTC’s UltraPixel technology, Sony sensor within iPhone 5, Sony’s own Exmor R and RS sensors, BlackBerry Z10’s Time Shift camera, etc.
Nokia PureView Technology
The current top of the line smartphone from Nokia is Lumia 920. It has two major technologies built in, Optical Image Stabilization and PureView. The first device to come up with PureView technology was last year’s release, Nokia PureView 808 with 41 MP camera, giving a resolution of 7728×5368. However, the default capture in PureView 808 camera is only at 5 MP. At 41 MP, the camera can take a huge image, while at 5 MP, only a part of that huge image is shown to the user. As a result, a user can easily zoom in up to 3x without losing quality as in digital zoom.
Digital zoom used in your smartphone’s camera has nothing to do with lens movement. It cannot give the clarity and detail as given by actual zooming, which has to be optical. In order to do optical zooming, you have to have a zoom lens in a larger camera housing as found in Samsung Galaxy Camera. With Nokia 808 PureView, the sensor itself is pretty large and capable of shooting a large image, and only a portion of that image is shown to you. Hence, a 3x lossless zoom as maintained by Nokia is possible.
In PureView technology, it uses something known as pixel oversampling. This means, the data from several pixels are used to form something Nokia calls a ‘super’ pixel. As a result, the camera is able to capture more light, and come up with a HDR effect on its images. This is one of the reasons why Nokia Lumia 920’s camera has been regarded as one of the best in the industry today.
The PureView technology is capable of shooting images with unmatched clarity in low light situations. Here is a comparison shoot:
More of such low light photographs can be found in Engadget’s gallery.
Earlier, around the time Nokia released Lumia 920, they came up with an ad supposedly shot with the camera, but was actually shot with a DSLR camera. It was a mistake.
Optical Image Stabilization
Nokia’s camera supports another technology known as Optical Image Stabilization. Unlike PureView, it is not a Nokia trademark, though. HTC phone, the latest HTC One, also supports OIS. It is also available in most of the high end cameras.
Imagine you are shooting a casual image, and you tripped and went out of focus for a moment. On a regular phone camera, you can imagine what would happen. The image would be out of focus and useless. On Lumia 920’s camera, it is a different story altogether. Lumia 920’s camera has something built into it known as OIS. It is a little piece of hardware that utilizes one of the phone’s sensors, the gyroscope.
A smartphone’s gyroscope is an MEMS (Micro Electro Mechanical System). This means, it is an electronic component with extremely tiny mechanical parts (moving parts). The gyroscope is an orientation element in the smartphone. This means, your smartphone feels the gravity and the angle in which you are holding it. It is also the technology behind display autorotation. Pretty smart, huh?
With the help of the gyroscope, the smartphone understands when you are shaking the camera during image capture. It just moves the lens to adjust focus. Take a look here, taken from HTC’s page on OIS.
Another way to stabilize the image is by software, aka Digital Image Stabilization (DIS). The difference is pretty much similar to optical zoom vs. digital zoom. Digital image stabilization also uses the gyroscope, but instead of moving the lens, it adjusts the data processed by the pixel array of the sensor to get a more focused image.
UltraPixel technology has been put forward by HTC through its HTC One smartphone. The technology is in many ways similar to Nokia’s PureView.
HTC One smartphone’s camera has a resolution of only about 4 megapixels. But these pixels are much larger than the regular pixels found in other smartphones. While iPhone 5’s pixels are 1.4 microns in size, HTC One’s pixels are as large as 2 microns. HTC calls them UltraPixels. These UltraPixels are capable of bringing in more light through each pixel, so that the picture is much better in low light conditions.
In PureView, the data from a number of pixels are used to form a ‘super’ pixel that improves low light photography, while in UltraPixel technology HTC has made pixels themselves large enough. In essence, both these technologies should have almost the same end result.
Apple iPhone Camera
There was a recent news story in Business Insider about ARGUS (Autonomous Real-Time Ground Ubiquitous Surveillance Imaging System), which is a surveillance camera that can be attached to drones like the Predator and the Global Hawk.
The interesting thing about this camera is that it uses the tiniest cameras possible, such as those inside iPhone 4S, shown here.
With many of these tiny cameras, ARGUS can achieve a whopping 1800 megapixel resolution in its images. That is an interesting story of how many small things can constitute one huge thing.
Apple iPhone 5’s camera has been touted far and wide as one of the best out there. Recent camera tests show it performing brilliantly in all kinds of lighting conditions. Apple calls its camera iSight, and it is almost as great as Nokia Lumia 920’s camera.
Apple has standing contract with Sony, which manufactures iPhone 5’s camera sensor. This was revealed in a teardown done by Chipworks.
iPhone 5 uses a faster shutter speed, up to 40 percent faster than iPhone 4S, and this has improved the quality of its images a lot. To protect the camera lens, Apple uses sapphire crystal, an extremely hard material that is highly scratch-resistant. iFixit did a teardown of the iPhone 5 and they found the camera to be well protected and clear.
BlackBerry Z10’s Camera
The recently released BlackBerry Z10 smartphone, marking sort of a rebirth for BlackBerry, uses a camera technology known as Time Shift.
This is a simple method in which the camera captures a short video instead of an image, and then it allows you to edit a face within that to get the best shot possible. This video explains it better:
Sony’s Exmor RS
Sony’s flagship smartphone, Xperia Z utilizes a technology known as Exmor RS. In August, last year, Sony announced this new sensor technology, in which CMOS sensors are placed in a stacked structure.
This particular technology is supposed to give supreme image quality in low light situations, and the camera module takes less space as compared to other smartphones since the sensor is much smaller.
As you can see, there are quite a number of camera technologies in the world today. Small cameras were big a few years ago. Even the Mars Rover Curiosity uses a 2 MP camera due to a number of reasons you can read here. But now is the time of high resolution cameras with great technologies. Going forward, you may get to see more and more technologies in smartphone photography.
[Image: Gizmodo, Akihabaranews, ePhotozine, GSMArena, Engadget, Strikefighterconsultinginc]