How to choose a smartphone with a good camera. What is camera interpolation on an Android smartphone? Image rotation example

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What is camera interpolation?

All modern smartphones have built-in cameras that allow you to enlarge the images obtained using special algorithms. From a mathematical point of view, interpolation is a method of detecting intermediate values of a number based on an available set of discrete parameters.

The interpolation effect is somewhat similar to the effect of a magnifying glass. Smartphone software does not increase image clarity or sharpness. It simply expands the picture to the required size. Some smartphone manufacturers write on the packaging of their products that the built-in camera has a resolution of "up to 21 megapixels". Most often, we are talking about an interpolated image, which is of low quality.

Interpolation types

Nearest Neighbor Method

The method is considered basic and belongs to the category of the simplest algorithms. Pixel parameters are determined based on one closest point. As a result of mathematical calculations, the size of each pixel is doubled. Using the nearest pixel method does not require a lot of computational power.

Bilinear interpolation

The pixel value is determined based on the data about the four nearest points captured by the camera. The result of the calculations is a weighted averaging of the parameters of the 4 pixels that surround the original point. Bilinear interpolation allows you to smooth transitions between color boundaries of objects. Images obtained using this method are significantly superior in quality to images interpolated by the nearest pixel method.

Bicubic interpolation

The color value of the desired point is calculated based on the parameters of the 16 nearest pixels. The points that are closest are given the maximum weight in the calculation. Bicubic interpolation is actively used by the software of modern smartphones and allows you to get a fairly high-quality image. Application of the method requires significant power of the central processor and high resolution of the built-in camera.

In order not to ask unnecessary questions:

Pros and cons

Science fiction films often show how a camera captures the face of a passer-by and transmits digital information to a computer. The machine enlarges the image, recognizes the photograph and finds the person in the database. In real life, interpolation does not add new detail to an image. It simply enlarges the original image using a mathematical algorithm, improving its quality to an acceptable level.

Interpolation defects

The most common defects that occur when scaling images are:

Stepping;
Blurriness;
Halo effect.

All interpolation algorithms allow maintaining a certain balance of the listed defects. Reducing the aliasing will necessarily cause an increase in image blur and halo appearance. Increasing the sharpness of the image will lead to an increase in the blurring of the picture, etc. In addition to the listed defects, interpolation can cause various graphic "noises" that can be observed at maximum magnification of the image. We are talking about the appearance of "random" pixels and textures unusual for the given subject.

The smartphone has an 8 MPix camera. What does interpolation up to 13 MPix mean?

Good day.

This means that your smartphone stretches the photo / image captured with the 8 MPix camera to 13 MPix. And this is done through the fact that real pixels are moved apart and additional ones are inserted.

But, if you compare the quality of the image / photo taken at 13 MP and 8 MP with interpolation up to 13, then the quality of the second will be noticeably worse.

To put it simply, the smart processor adds its own pixels to the active pixels of the matrix when creating a photo, as if calculating the picture and drawing it up to a size of 13 megapixels .. At the output we have a matrix of 8 and a photo with a resolution of 13 megapixels. The quality does not improve much from this.

This means that the camera can take a picture up to 8 MPIX, but programmatically it can increase pictures up to 12 MPIX. This means that it programmatically increases, but the image does not become better, the image will be exactly 8 MPIX. This is purely a gimmick of the manufacturer and such smartphones are more expensive.

This concept assumes that the camera of your device will still take photos on 8 MPIX, but now you can programmatically increase it to 13 MPIX. At the same time, the quality does not become the best. It's just that the space between the pixels is clogged up that's all.

This means that in your camera, as there were 8 MPIX, they remain - no more and no less, and everything else is a marketing ploy, a scientific fool of the people in order to sell the product at a higher price and no more. This function is useless, the quality of the photo is lost during interpolation.

On Chinese smartphones, this is now used constantly, just a 13MP camera sensor costs much more than 8MP, which is why they put it at 8MP, but the camera application stretches the resulting image, as a result, the quality of these 13MP will be noticeably worse if you look at the original resolution ...

In my opinion, this function is useless at all, since 8MP is quite enough for a smartphone, in principle, 3MP is enough for me, the main thing is that the camera itself is of high quality.

Camera interpolation is a trick of the manufacturer, so they artificially inflate the price of a smartphone.

If you have an 8 MPIX camera, then it can take a corresponding picture, interpolation does not improve the quality of the photo, it just increases the size of the photo to 13 megapixels.

The point is that the real camera in such phones is 8 megapixels. But with the help of internal programs, the image is stretched to 13 megapixels. In fact, it doesn't get to the actual 13 megapixels.

Megapixel interpolation is software blurring of a picture. Real pixels are moved apart, and additional ones are inserted between them, with the color of the average value from the colors of the spaced ones. Nonsense, self-deception that no one needs. The quality does not improve.

Interpolation is a way to find intermediate values
If this is all translated into a more human language, applicable to your question, then you get the following:
- the software can handle (enlarge, stretch)) files up to 13 MPIX.

Up to 13 MPix - it can be 8 MPix real, just like yours. Or 5 MPix real. The camera software interpolates the graphic product of the camera up to 13 MPix, not enhancing the image, but electronically enlarging it. Simply put, like a magnifying glass or binoculars. The quality does not change.

Camera interpolation is an artificial increase in the resolution of an image. It is the image, not the size of the matrix. That is, this is special software, thanks to which a picture with a resolution of 8 megapixels is interpolated to 13 megapixels or more (or less). By analogy, camera interpolation is like a magnifying glass or binoculars. These devices enlarge the image, but do not make it better or more detailed. So if interpolation is indicated in the specifications for the phone, then the actual resolution of the camera may be lower than stated. This is neither bad nor good, it just is.

Interpolation was invented to increase the size of the image, nothing more. This is now a ploy by marketers and manufacturers who are trying to sell a product. They indicate in large numbers on the advertising poster the resolution of the phone's camera and position it as an advantage or something good. Not only does the resolution itself not affect the quality of photos, it can also be interpolated.

Literally 3-4 years ago, many manufacturers were chasing the number of megapixels and in various ways tried to cram sensors with as many sensors as possible into their smartphones. This is how smartphones appeared with cameras with a resolution of 5, 8, 12, 15, 21 megapixels. At the same time, they could take pictures like the cheapest soap dishes, but buyers, having seen the sticker "18 Mp Camera", immediately wanted to buy such a phone. With the advent of interpolation, selling such smartphones has become easier due to the possibility of artificially adding megapixels to the camera. Of course, photo quality began to improve over time, but certainly not because of resolution or interpolation, but because of natural progress in terms of sensor and software development.

What is camera interpolation in a phone, technically, because all the text above described only the main idea?

With the help of special software, new pixels are "drawn" on the image. For example, to enlarge the image by 2 times, a new line is added after each line of pixels in the picture. Each pixel on this new line is filled with color. The fill color is calculated by a special algorithm. The very first way is to fill a new line with the colors of the nearest pixels. The result of such processing will be terrible, but this method requires a minimum of computational operations.

Another method is most often used. That is, new lines of pixels are added to the original image. Each pixel is filled with color, which, in turn, is calculated as the average of neighboring pixels. This method gives better results, but requires more computational operations. Fortunately, modern mobile processors are fast, and in practice the user does not notice how the program is editing the image, trying to artificially increase its size. smartphone camera interpolation There are many advanced interpolation methods and algorithms that are constantly being improved: the transition boundaries between colors are improved, the lines become more accurate and clear. It doesn't matter how all these algorithms are built. The very idea of camera interpolation is trivial and is unlikely to take root in the near future. Interpolation cannot make an image more detailed, add new details, or improve it in any other way. Only in movies does a small blurry picture become clear after applying a couple of filters. In practice, this cannot be.
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Sensors are devices that detect only grayscale (gradations of light intensity - from completely white to completely black). To enable the camera to distinguish colors, an array of colored filters is applied to the silicon using a photolithography process. In sensors that use microlenses, filters are placed between the lens and the photodetector. In scanners that use trilinear CCDs (three adjacent CCDs that respond to red, blue and green, respectively), or high-end digital cameras, which also use three sensors, light of its specific color is filtered on each sensor. (Note that some cameras with multiple sensors use combinations of several colors in filters, rather than the standard three). But for single-sensor devices like most consumer digital cameras, color filter arrays (CFA) are used to handle different colors.

In order for each pixel to have its own primary color, a filter of the corresponding color is placed above it. The photons, before hitting a pixel, first pass through a filter that only lets through the waves of their own color. Light of a different length will simply be absorbed by the filter. Scientists have determined that any color in the spectrum can be obtained by mixing just a few primary colors. There are three such colors in the RGB model.

Different color filter arrays are developed for each application. But in most digital camera sensors, the most popular are the Bayer pattern filter arrays. This technology was invented in the 70s by Kodak, when it was conducting research in the field of spatial separation. In this system, the filters are alternately staggered, and the number of green filters is twice as many as red or blue. The order is such that the red and blue filters are positioned between the green ones.

This quantitative ratio is explained by the structure of the human eye - it is more sensitive to green light. And the checkerboard pattern ensures the same color images no matter how you hold the camera (vertically or horizontally). When reading information from such a sensor, the colors are recorded sequentially in lines. The first line should be BGBGBG, the next line should be GRGRGR, etc. This technology is called sequential RGB.

In CCD cameras, the combination of all three signals together occurs not on the sensor, but in the imaging device, after the signal has been converted from analog to digital. In CMOS sensors, this alignment can occur directly on the chip. In any case, the primary colors of each filter are mathematically interpolated based on the colors of the neighboring filters. Note that in any image, most of the dots are a mixture of primary colors, and only a few truly represent pure red, blue, or green.

For example, to determine the influence of neighboring pixels on the color of the center, linear interpolation will process a 3x3 matrix of pixels. Take, for example, the simplest case - three pixels - with blue, red and blue filters, arranged in one line (BRB). Let's say you are trying to get the resulting color value of a red pixel. If all colors are equal, then the color of the central pixel is calculated mathematically as two parts of blue to one part of red. In fact, even simple linear interpolation algorithms are much more complex, they take into account the values of all surrounding pixels. If the interpolation is bad, then you get teeth at the boundaries of the color change (or color artifacts appear).

Note that the word "resolution" in the field of digital graphics is used incorrectly. Purists (or pedants, whichever you prefer) familiar with photography and optics know that resolution is a measure of the ability of the human eye or instrument to distinguish between individual lines on a resolution grid, such as the ISO grid shown below. But in the computer industry, it is customary to call the number of pixels by resolution, and since this is the custom, we will also follow this convention. Indeed, even the developers call the number of pixels in the sensor resolution.

Let's count?

The image file size depends on the number of pixels (resolution). The more pixels, the larger the file. For example, the image of VGA standard sensors (640x480 or 307200 active pixels) will occupy about 900 kilobytes in uncompressed form. (307200 pixels by 3 bytes (R-G-B) = 921600 bytes, which is approximately equal to 900 kilobytes) An image of a 16 MP sensor will take up about 48 megabytes.

It would seem that it is so - to count the number of pixels in the sensor to determine the size of the resulting image. However, camera manufacturers provide a bunch of different numbers, and each time they claim that this is the true resolution of the camera.

Total pixels include all pixels physically present on the sensor. But only those that participate in the acquisition of the image are considered active. About five percent of all pixels will not participate in the image acquisition. These are either defective pixels or pixels used by the camera for another purpose. For example, masks may exist to determine the level of dark current or to determine the aspect ratio.

Aspect Ratio - the ratio between the width and height of the sensor. In some sensors, for example, with a resolution of 640x480, this ratio is 1.34: 1, which corresponds to the aspect ratio of most computer monitors. This means that the images created by such sensors will fit exactly on the monitor screen, without pre-cropping. In many cameras, the aspect ratio is the same as the format of traditional 35mm film, where the ratio is 1: 1.5. This allows you to take pictures of a standard size and shape.

Resolution Interpolation

In addition to optical resolution (the real ability of pixels to respond to photons), there is also a resolution increased by a software and hardware complex using interpolating algorithms. As with color interpolation, resolution interpolation analyzes the data of neighboring pixels mathematically. In this case, as a result of interpolation, intermediate values are created. Such "embedding" of new data can be done quite smoothly, while the interpolated data will be something in between, between the real optical data. But sometimes, during such an operation, various interference, artifacts, and distortions may appear, as a result of which the image quality will only deteriorate. Therefore, many pessimists believe that resolution interpolation is not at all a way to improve image quality, but only a method of enlarging files. When choosing a device, pay attention to the resolution indicated. Don't be too happy about high interpolated resolution. (It is marked as interpolated or enhanced).

Another image processing process at the software level is Sub-sampling. In fact, this is the reverse process of interpolation. This process is carried out at the stage of image processing, after the data has been converted from analog to digital form. This deletes the data of the different pixels. In CMOS sensors, this operation can be carried out on the chip itself, temporarily disabling the reading of certain lines of pixels, or reading data only from selected pixels.

Downsampling has two functions. First, to compact the data - to store more images in memory of a certain size. The smaller the number of pixels, the smaller the file size, and the more pictures you can fit on a memory card or in the internal memory of the device, and the less often you have to download photos to a computer or change memory cards.

The second function of this process is to create images of a specific size for specific purposes. Cameras with a 2MP sensor are quite tough to take a standard photo of 8x10 inches. But if you try to send such a photo by mail, it will noticeably increase the size of the letter. Downsampling allows you to process the image so that it looks good on your friends' monitors (if you don't set the goal for detail) and at the same time is sent quickly enough even on machines with slow connections.

Now that we are familiar with the principles of sensors, we know how the image is obtained, let's look a little deeper and touch on more complex situations that arise in digital photography.

Main characteristics

Matrix

A type
The matrix installed in the webcam can be of two types: CCD and CMOS.
Traditionally, CCDs are considered to provide higher image quality, better color reproduction, and less noise. However, the cost of such a matrix is much higher than another type of matrix.
CMOS-matrix is manufactured according to the technology traditional for integrated circuits, so it costs less. It should be noted that modern CMOS sensors have almost caught up with their CCD counterparts in image quality.

Megapixels
from 0.1 to 16
The more light-sensitive elements (pixels) are located on the webcam matrix, the more accurate and detailed the image can be obtained.
The simplest models of webcams have a matrix of 0.1 million pixels, which allows you to get an image with a resolution of 352x288. This camera can only be used for communication via the Internet.
Cameras with a 0.3-megapixel matrix are capable of displaying 640x480 pixels. The picture when communicating via the Internet will be much better. In addition to video conferencing, such a camera can be used to shoot short videos.
Cameras with a resolution of 1.3-2 million pixels. can also be used as cameras and take photos with decent resolution.

Color depth
10 to 32 bit
The more bits are used to convey color, the more different tints the camera can display.
Cameras with 24-bit color depth (8-bit for each color) have the potential to provide excellent color reproduction. However, other parameters also affect the overall picture quality: properties of the camera lens, resolution of the photosensitive matrix, etc.
In some models of webcams, manufacturers claim to support 32-bit color.

Permission

Resolution (video)
The higher the maximum resolution of the webcam matrix in video recording mode, the more accurate and detailed the image can be obtained. Resolution - the number of dots that make up the image horizontally and vertically.
For those who plan to use a webcam only for video conferencing over the Internet, both the simplest models with a resolution of 352x288 and modifications with a higher resolution of 640x480 are suitable.
Among modern cameras, there are also models with an even higher resolution. They can be used for video recording at home.

Resolution (photo)
Resolution refers to the number of dots that make up the image horizontally and vertically. The higher the resolution of the webcam in photography mode, the more accurate and detailed the image can be obtained.
If you plan to use your webcam in photo mode, then pay attention to models with a resolution of 1280x1024 and 1600x1200.
The photo resolution of a webcam is often higher than its resolution in video transmission mode.

Interpolated Resolution (Video)
The higher the maximum interpolated resolution of the webcam in video recording mode, the more accurate and detailed the image can be obtained. Resolution - the number of dots that make up the image horizontally and vertically.

Interpolated resolution (photo)
The higher the maximum interpolated resolution of the webcam in photo shooting mode, the more accurate and detailed the image can be obtained. Resolution - the number of dots that make up the image horizontally and vertically.
Interpolated (or artificially increased) resolution is obtained programmatically using mathematical algorithms. In this case, the amount of detail in the image remains unchanged. An interpolated resolution image usually looks slightly better than the original, but you shouldn't take high values seriously.

Interpolated megapixel resolution (photo)
from 1.2 to 20 Mpix
In some cases, manufacturers indicate not the vertical and horizontal resolution, but the number of pixels that make up the matrix with this resolution.

Frame frequency

Maximum
from 9 to 90 Hz
The maximum frame rate in video mode determines the quality of the video stream. With a slow frame rate, the image is updated not often enough and moving objects on the screen move in jerks.
At 15 frames per second, jerky movement is very noticeable on the screen; at 30 fps, the movement becomes smooth.
The frame rate in many cases depends on the resolution of the transmitted video. For example, at 352x288, a webcam is capable of generating a video stream at a frame rate of 30 Hz, while at a resolution of 640x480, the frame rate is reduced to 15 Hz.
It should be noted that the quality of the image transmitted over the Internet depends not only on the webcam itself, but also on the speed and reliability of the network connection.

For 352x288
15 to 60 Hz
Maximum frame rate in video mode at 352x288 resolution (For details, see "Maximum frame rate").

For 640x480
15 to 60 Hz
Maximum frame rate in video mode at 640x480 resolution (For details, see "Maximum frame rate").

For 1280x720
8 to 90 Hz
Maximum frame rate in video mode at a resolution of 1280x720 (For details, see "Maximum frame rate").

For 1280x1024
from 6 to 30 Hz
Maximum frame rate in video mode at a resolution of 1280x1024 (For details, see "Maximum frame rate").

For 1600x1200
5 to 30 Hz
Maximum frame rate in video mode at 1600x1200 (see "Maximum frame rate" for details).

For 1920x1080
5 to 60 Hz
Maximum frame rate in video mode at 1920x1080 resolution (See "Maximum frame rate" for details).

Focusing

Automatic
The autofocus webcam delivers clear, focused images every time. For example, if, while communicating on the Internet, a person accidentally moves away from the camera and leaves the field of focus, the autofocus itself will reconfigure the optical system, and the image will be sharp again. It should be noted that most of the simplest models of webcams do not have such a function.

Manual
To get a sharp and clear image, some webcam models are equipped with a manual focus function. For simple models, a ring on the camera lens is used for this. With "advanced" cameras, focusing can be adjusted directly in the program that controls the operation of the device. These models often have an automatic focusing function (see "Automatic focusing"), while manual focusing is used in cases where the automation cannot cope with the task at hand.

Zoom

Optic
4 to 10x
Some webcam models have a zoom lens.
Changing the value of the focal length leads to a visual "approach" or "removal" of the subject. The optical zoom ratio shows how many times the lens can change the scale of the shooting. The higher the number, the more options the operator using the webcam has.

Digital
from 2 to 10x
Some webcam models have a digital zoom function that allows you to magnify the image, which is equivalent to getting closer to your subject.
Digital image enlargement is performed programmatically by increasing the pixel size of the image. With a large matrix resolution, such an increase can be performed without a noticeable deterioration in image quality.
The zoom ratio shows how many times the lens can change the scale of the shooting.

Viewing angles and rotation

Lens angle of view
from 42 to 180 degrees
The angle of view of a webcam lens determines how much of the space falls into the frame. It depends on the size of the photosensitive matrix and the parameters of the camera lens.
The wide-angle lens (70-90 degree viewing angle) allows you to capture more objects without compromising image quality.

Tilt angle
from 25 to 270 degrees

Tilt angle up
15 to 60 degrees
Many models are designed with the ability to tilt the camera, which makes it possible to quickly redirect the lens in the desired direction. The larger the tilt angle, the more convenient it is to work with the camera.

Downward tilt angle
15 to 90 degrees
Many models are designed with the ability to tilt the camera, which makes it possible to quickly redirect the lens in the desired direction. The larger the tilt angle, the more convenient it is to work with the camera.

Horizontal rotation angle
from 55 to 360 degrees
Many models are designed to allow the camera to rotate horizontally while keeping the stand unchanged. Some webcams can be rotated 360 degrees around a vertical axis. The larger the angle of rotation, the more comfortable it is to work with the camera.

Functionality

Connection
To connect a webcam to a computer, USB 1.1 or USB 2.0 interfaces are used.
For USB 1.1, the maximum data transfer rate is only 12 Mbps, which usually results in the 640x480 video transfer rate being limited to 15 frames per second. USB 1.1 can be found in the simplest webcam models.
USB 2.0 provides a transmission speed of 480 Mbps, which no longer imposes tangible restrictions on the quality of the video image. For example, you can stream video at 640x480 pixels at 30 frames per second.

Wi-Fi
Support for a web-camera Wi-Fi connection, thanks to which the user can broadcast the video image wirelessly to a tablet, smartphone or computer, conduct online broadcasting and control the web-camera from the connected device.

Microphone
Depending on the model, the webcam may have a built-in microphone or an optional microphone. Some of the simplest models may not have a microphone.
With a built-in microphone in the webcam, the signal is transmitted via the USB interface along with the video signal, so there is no need for an additional cable. The microphone sensitivity is adjusted using the program that controls the operation of the webcam.
In some cases, the webcam does not have a built-in microphone, but it comes bundled. The main disadvantage of such a microphone is that it must be separately connected to the corresponding connector of the computer sound card. Sometimes cameras are equipped not with a separate microphone, but with a headset (see "Headset Included").
The simplest models may not have a microphone at all. To transfer sound, you will need to purchase a microphone or headset separately and connect this device to your sound card.

Mount on the monitor
In order to free up space on the table, many models of webcams can be mounted on the monitor using a special mount.

Mechanical tracking drive
The mechanical tracking drive rotates the camera using a special mechanism and allows you to automatically keep the user's face, which is in the camera's field of view, in the center of the transmitted image.
For many models, the face tracking function is implemented using software (see "Face tracking function"). The range within which this function works is very limited. The mechanically driven models have much better user tracking.

Snapshot button
The button on the webcam body for taking a photo is similar to the shutter button in a conventional camera. Thus, to turn a webcam into a camera, it is enough to point the lens at the subject, press a button and get a photo.

Face tracking function
The face tracking function automatically keeps the user's face, which is in the camera's field of view, in the center of the transmitted image. This simplifies the choice of camera location and improves the convenience of video conferencing.
For most models, the face tracking function is implemented using software. However, there are also cameras on the market, in which the tracking of the user's face is performed using a special drive (see "Mechanical tracking drive").

Curtain
Constructively, the presence of a shutter on the camera lens will protect the lenses from dust, and the user from accidental / unforeseen recording.

Backlight
The built-in backlight is designed to improve the image in low light conditions.

Compatibility

Windows compatible
Availability of drivers for working with operating systems from the Windows family.

MacOS compatibility
Availability of drivers for working with operating systems from the MacOS family.
The parameter will be important for those who plan to connect a webcam to an Apple computer (compatible with macOS). While Windows support almost all webcams, the manufacturers guarantee work with MacOS only for some.

Linux Compatibility
Availability of drivers for working with operating systems from the Linux family.
The parameter will be important for those who plan to connect a webcam to a Linux computer. While Windows support almost all webcams, manufacturers guarantee work with Linux only for some.

Compatible operating systems
Detailed list of compatible operating systems with name and version.

Additional Information

Case included
The cover will be useful for those who plan to take a webcam on trips.

Headset included
The headset is convenient to use for communication via the Internet. Headsets are often supplied with webcams that do not have a built-in microphone (see "Microphone").

Length of cable
from 0.45 to 5 m
The longer the cable connecting the webcam to the computer, the more freely you can move the webcam. If you plan on using your camera for home video filming, then a long cable will come in handy.

Dimensions (edit)

Width
from 20 to 185 mm

Height
from 15 to 236 mm
This parameter can be important for those who plan to take a webcam on trips.

Depth
from 9 to 183 mm
This parameter can be important for those who plan to take a webcam on trips.

Weight
from 23 to 350 g
This parameter can be important for those who plan to take a webcam on trips.