What is hdr in iPhone, the principle of operation and all aspects of using this technology. What is HDR in a phone camera

The cameras of the Pixel and Nexus smartphones have never been anything special, but over the past four years they have taken a powerful leap forward and now occupy the first lines of the ratings. Why did it happen? Because Google has implemented a software post-processing engine called HDR+. In this article, we will explain how it works and how to enable HDR+ on your smartphone, regardless of brand.

What is HDR

To fully understand how HDR+ works, you will first need to understand regular HDR.

The main problem of all smartphone cameras is the small size of the matrix (or rather, photocells) and, as a result, insufficient coverage of the dynamic range. To correct this drawback, the HDR (High-Dynamic Range) algorithm was developed, the principle of which is as follows: the camera takes a frame with a standard exposure level for a given scene, then takes an underexposed frame, on which only overexposed areas of the original image will be clearly visible, then An overexposed image in which only the dark details of the original image are visible, and everything else is overexposed. Further, the images are superimposed on each other and combined using special algorithms, the quality of which depends on the manufacturer of the camera software. The result is a picture with good detail in both the shadows and the brighter areas.

The disadvantages of HDR are obvious: a long shooting time leads to the fact that moving objects caught in the frame will double, and even a slight shaking will blur the picture.

What is HDR+

Smart heads have come up with an algorithm devoid of the shortcomings of HDR. However, it has only one name in common with HDR.

HDR+ stands for High-Dynamic Range + Low Noise. He gained his fame for a number of outstanding features: the algorithm is able to eliminate noise with virtually no loss of detail, improve the quality of color reproduction, which is extremely important in low light and at the edges of the frame, at the same time it greatly expands the dynamic range of photography. HDR +, unlike standard HDR, is almost not afraid of smartphone shaking and movement in the frame.

The first HDR+-enabled smartphone was the Nexus 5. Due to not the best white balance and small aperture (f2.4), the camera of this smartphone was considered nothing more than a strong middling. Everything changed with the release of the Android 4.4.2 update. It was it that brought with it support for the HDR + mode and the amazing quality of night shots. Although they were not very bright across the entire field of the frame, thanks to HDR + they practically did not contain noise while maintaining small details and had excellent (for smartphones in 2013) color reproduction.

History of HDR+

So how does a company that has never been into cameras come up with an algorithm that works wonders using conventional, by flagship standards, Nexus and Pixel cameras?

It all started in 2011, when Sebastian Thrun, CEO of Google X (now just X), was looking for a camera for Google Glass augmented reality glasses. The weight and size requirements were very strict. The size of the camera matrix had to be even smaller than in smartphones, which would have an extremely bad effect on the dynamic range and would lead to a lot of noise in the photo.

There was only one way out - to try to improve the photo programmatically, using algorithms. This task was to be solved by Marc Levoy, a lecturer in the computer science department at Stanford University, an expert in computational photography. He focused on software-based image capture and processing technology.

Mark formed a team known as Gcam, which began to study the Image Fusion method (fusion of images), based on combining a series of images into one frame. Photos processed using this method turned out to be brighter and sharper, with a small amount of noise. In 2013 technology debuted in Google Glass, and then, in the same year, renamed HDR +, appeared in the Nexus 5.

How HDR+ works

What about dynamic range expansion? As we already know, using a fast shutter speed saves us from overexposed places. It remains only to remove the noise in the dark area using the previously described algorithm.

At the final stage, the resulting image is post-processed: the algorithm minimizes vignetting due to light hitting the matrix at an oblique angle, corrects chromatic aberration by replacing pixels at high-contrast edges with neighboring ones, increases green saturation, shifts blue and magenta hues towards blue, enhances sharpness (sharping ) and performs a number of other steps to improve the quality of the photo.

On the left is a photo from a stock Samsung camera in HDR, and on the right is a photo created in Gcam in HDR +. It can be seen that the algorithm sacrificed the detail of the sky to draw objects on the ground.

Camera improvements and HDR support are one of the promised changes in iOS 4.1. HDR mode (High Dynamic Range in English - high dynamic range) is an increase in the dynamic range of a picture taken with a digital camera.

What is HDR mode

Let's imagine the following situation. Early morning or evening in a room with natural light. You perfectly see all the details of the room and the surrounding landscape outside the window. But when you try to take a photo, you get either a detailed interior and an overly bright window, or a dark room and a fairly well-designed street landscape. The new camera mode will avoid this and get the result that corresponds to reality.

Now your iPhone will take three frames at a time and combine the images in the final shot. Using the mode makes it possible to balance the tonality of surrounding objects, as a result of which the image more fully reflects the real picture and simply looks better. Let's try to figure out in which cases the application of the effect allows you to get a better picture.

When can I use the HDR graphic effect

Always use this mode in the following cases:

• in landscape photography (helps to smooth out the contrast between the bright bright sky and the dark earth);
• in portrait shooting in bright daylight or strong artificial lighting (removes the effect of a whitened face);
• when the lighting is not enough (dark room and light from the window).
• When not to use the mode:
• when shooting moving objects (considering that the final image is made up of three intermediate ones, the image may turn out to be blurry);
• if you want a high-contrast shot (many images look better with strong detail contrast, and using the mode smoothes it out a lot);
• if you want to take a rich and bright photo (using the mode makes the image paler).

To turn on HDR on iPhone, simply tap on the corresponding icon located at the top of the screen in Capture mode. Now you can take a picture as usual. The phone will take a little longer to process and save the image.

Practice shows that the graphic effect is especially useful when shooting landscapes. A conventional camera often spoils the sky, making it white and not conveying a rich blue tint at all. The mode allows you to avoid this and make a very high-quality shot.

Finally, it should be noted that any artificial modes and filters must be used with caution. If you want to be sure that the resulting image will not be corrupted, reframe without using HDR. In the future, the resulting image can be edited using a special program. In addition, after a while, this approach will show whether you need to use artificial modes or not.

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Rodion Danilov

Owners of the latest smartphone models have probably seen that they have a photo application with support for HDR (High Dynamic Range - high dynamic range ). More experienced users know what HDR is, but not everyone understands how and in what cases this feature is best used. In the “Instructions” section, we will try to clear up some confusion and show you how to get the most out of HDR when shooting on a mobile phone.

As you know, the human eye can see a much more "high dynamic range" of the scene than any camera, not to mention the camera of a mobile phone. We can equally well distinguish the small details of a dark building against a bright sky and, for example, an airplane flying high above it. But we all know what happens when you take a picture of a building with your phone: it turns out to be too dark with very little detail.

Photo with sky exposure

Of course, we could try to eliminate this problem by setting the exposure on the building itself, highlighting the area with it on the screen. With this approach, the decor of the building is seen quite well, but the sky in the photo turned into an overexposed, blurry white spot.

Photo with exposure of the building

Our goal is to combine the best features of the two photos, creating one image where both the building and the clouds look great. This is exactly what HDR technology offers. Photos taken with HDR are essentially several combined shots taken at different exposures.

The default iPhone photo app has built-in HDR functionality. You can enable HDR by clicking on the option button in the "camera". When HDR mode is enabled, iPhone will automatically take HDR photos. Note that this takes longer than normal shooting.

However, the built-in iPhone application gives a rather “weak” result, and you can take much better pictures using special programs.

Photo taken with Pro HDR on iPhone 5
Photo taken with default app on iPhone 5

One of the most popular and user-friendly HDR photo apps is Pro HDR.(for iOS - 66 rubles; for Android - 61.75 rubles). However, there are also free versions with limited functionality.

The Pro HDR app offers two modes: automatic and manual. If you select Auto, the app will analyze the scene, capture a dark exposure (with detailed highlights but less detail in the shadows) and a bright exposure (with detailed shadows but less detail in the bright areas) and blend the two images.

Some photos may not look natural enough. To add realism to your shot, use the five sliders in the simple and intuitive settings panel. They allow you to adjust brightness, contrast, saturation, warmth, and tint. Auto mode is fine for most situations; manual mode is necessary only when shooting the most contrasting scenes.

Settings panel interface in Pro HDR

Please note that HDR photos do not always look better than those taken in standard mode. Try to save both HDR and "normal" shots so that you can choose the best ones later.

Using HDR mode is inappropriate when shooting on the move. Because HDR combines multiple exposures of the same scene; and if these very scenes change, you will end up with the most unpredictable result. Try to shoot while leaning on something stable or using a tripod.

HDR photo taken on the move

The desire of smartphone manufacturers to make their products more attractive to buyers has led to the fact that it is now quite difficult to find a device that would not have a built-in digital camera. Dozens of megapixels, complex image processing algorithms, automatic range adjustment ... It would seem that it is enough to select the desired frame and press a button, and the automation will do the rest.

Unfortunately, this is only partly true. So, for example, an attempt to shoot a building against a bright blue sky will lead to an overall excessive darkening, since in this case the brightest element is selected as the reference point, relative to which the rest of the parameters are set. If you intervene in the work of the algorithms and manually specify the exposure, then the result may be a building with acceptable brightness in the picture, but a white spot instead of the sky. To overcome this, there is a special HDR mode implemented in almost every modern digital camera, including models in smartphones. Having learned to work with it, you can be sure that the quality of the pictures will be perfect. This abbreviation stands for Dynamic Range Extension. Thus, to the question: “in the phone’s camera?” you can answer like this: "This is a special frame processing function designed to improve images by combining one final from several intermediate ones." In general, a rather interesting opportunity, with which every owner of a modern smartphone is simply obliged to familiarize himself.

What is HDR in a phone camera

In fact, the principle of operation of this mode is quite simple. HDR shooting assumes that the camera takes not one, but several frames at once, while focusing on objects with different levels of illumination.

Then the central processor selects images with average values ​​and combines them into one, which is offered to the user. Thanks to the use of this simple method, you can forget about too bright and not enough light objects in one frame - everything is in balance. Since this solution is completely software, to use it, you just need to install an application that has a similar shooting mode. Note that not all cameras pre-installed in the basic firmware of smartphones have this feature.

Nuances of use

At the same time, it is important to understand that the HDR mode is still not a panacea. Even by using it, the owner does not become a professional photographer. The main problem is this: since the final image is formed from several intermediate ones, the apparatus itself and the objects in the frame must be motionless.

Otherwise, an unpleasant HDR effect may occur, in which everything in the picture looks blurry, doubles, etc. When working with this mode, it is recommended to use a tripod.

The next feature to consider is that in some cases taking a picture with an average brightness is inappropriate. For example, silhouettes in the twilight, according to the photographer's intention, should remain the same indefinite shadows, and not people in gray raincoats. HDR shooting does not allow for this.

And finally, the brightness and contrast of pictures taken in this mode are generally slightly lower than in photographs taken in the usual way. Sometimes this is very critical.

HDR Pro

Within the framework of the article, it is useless to try to describe all existing programs for smartphones that implement an extended range shooting mode, since there are dozens of them.

Let's point out just a few. One of the most famous programs in this group is HDR Pro Camera. Despite the fact that the release of new versions is discontinued (the latest is 2.35), the reviews about this application are the most flattering. An additional plus is guaranteed performance even on the outdated Android 2.2, which for some may be a decisive factor. Once launched, the user has the option to select automatic or manual mode. In the second case, you can use the sliders on the screen to pre-adjust the brightness, contrast, color temperature with which pictures will be taken. The program is distributed on a paid basis, but the cost is very democratic - less than 60 rubles.

SNAP camera

Perhaps everyone who has set himself the task of choosing a good photography program for himself has come across a solution from the developer Marginz Software. Snap Cam enjoys well-deserved popularity among many, which is explained by several factors. Among them are support and timely release of new versions; some features are unique; the program has absorbed almost everything that may be of interest to both professional and novice photographers. In particular, it is when working with it that it is easiest to understand what HDR is in a phone camera. To activate the mode after installation and launch, you must select HDR by rotating the graphic settings wheel (version 7.x.x). It remains to take a picture. By default, three frames with different exposures will be saved, among which you can choose the best one. The function of saving intermediate shots, if it is not needed, is deactivated in the settings - the HDR section. In this case, the entire shooting process takes place completely automatically, except, of course, pressing a button. Fans of "playing around" with the settings may be interested in focusing between intermediate frames, as well as milliseconds of delay. The program allows you to adjust the clarity, brightness, image resolution, cropping, etc. A license is required.

Basic functionality

The demand for HDR mode has led more and more smartphone manufacturers to include a camera application in their operating systems, which natively provides the ability to take pictures with a wide dynamic range. True, when using stock (basic) solutions, there is no need to talk about the abundance of any additional settings. For example, in the popular build of CyanogenMod, clicking on the three dots of the menu opens a window where you can enable or disable the use of HDR mode. Parallel operation of this function and the flash is not possible. It is worth noting that very often an inexpensive one shooting in normal mode allows you to get better photos than a more expensive one, but with a low-quality matrix.

"Open camera"

That's right - Open Camera - is the name of an application that also deserves the closest attention from photo lovers. There are no less settings in it than in the above Snap. True, to activate the HDR mode, a beginner has to study all the items in the settings. In fact, the "magic button" can be accessed by pressing the dot icon in the top on-screen menu. Among the items in the "Scene" list is HDR. The quality of the final image is excellent, but the processing speed is one of the slowest among similar solutions. Perhaps, in smartphone models with productive processors, this delay is leveled. To understand what HDR is in a phone camera, it is recommended to practice choosing different shooting modes and compare the result.

The technology is based on advanced camera sensors, the power of the neural engine of the A12 Bionic processor, machine learning, artificial intelligence and the latest computational photography technologies. With Smart HDR, anyone can take beautiful pictures with great light and dynamic range.

All you have to do is press a button and your iPhone does the rest. This is possible thanks to Apple's own CPU, GPU and ISP. Now you can take amazing pictures effortlessly.

Unlike regular HDR and Auto HDR, Smart HDR is not available on older iPhones. It is supported only by the ruler. This is due to the fact that older models do not have fast enough sensors. With Smart HDR, you can freeze a moment in time in great detail.

What meansHDR

HDR stands for High Dynamic Range - high dynamic range.

This is a digital photography technique that helps you take great photos with high contrast. HDR processes photos in such a way as to increase their dynamic range. Best of all, the technology copes with shooting shaded objects against a bright background, like a sunny sky.

On conventional DSLR cameras, you have to choose whether the focus will be on the subject or on the background. With HDR, you can capture both elements. When HDR is active, your device takes three photos at different exposure levels and then combines the best elements of each photo into one shot. The technology is especially useful when shooting with poor lighting.

The images below show you how HDR works. On the left, the exposure is adjusted to the subject, so the sky is too bright, and on the right, the exposure is adjusted to the sky, so the subject is too dark.

As you can see for yourself, the technology took the best of both shots and combined them into one photo that came out with good contrast and detail.

And thanks to Apple's wide color gamut screens on iPhone and iPad, HDR shots look 60% better.

Auto HDRon the

On iPhone X, HDR technology works on autopilot. It is supported by both the main and front cameras of the iPhone X. The function is activated by itself when it is needed, but you can turn it off if you wish.

We already mentioned above that thanks to the improved camera sensors and processors of the iPhone XS and iPhone XR, the HDR feature has become even better.

Using the full power of new cameras, Apple has developed an advanced version of Auto HDR, which is called Smart HDR.

Smart HDR

Smart HDR is activated automatically to improve the quality of photos depending on the shooting conditions. Unlike previous versions of HDR, Smart HDR also works with portrait shots, panoramic shots, Live Photos, and action shots, as shown below.

The Smart HDR feature is so good that almost every photo on the iPhone XS/Max/Xr is taken using it. All HDR shots on older models are marked with an "HDR" icon in the corner, while on new smartphones, Smart HDR is essentially used for all photos, and the most intense ones are marked with an icon.

Below you can see a comparison of iPhone XS and iPhone X technology. The pictures really show how much better HDR technology has become.

Smart HDR can be disabled in the camera settings. To manage HDR manually:

• iPhone XS, iPhone XS Max AndiPhone xr: Settings → Camera → Smart HDR.
• iPhone X, iPhone 8 & iPhone 8 Plus: Settings → Camera → Auto HDR.
• Old models: Settings → Camera → HDR.

On all iPhones that support HDR, HDR can be controlled manually in the Camera app. Just click the icon HDR top and enable/disable the function.

All iPhone models older than iPhone X retain original shots along with HDR shots because HDR does not always work correctly on them. Accordingly, it clogs the memory of devices.

If you only want to save the HDR version, go to Settings → Camera and click on the switch next to Leave the original. Newer models with advanced sensors do not retain original shots by default.