How appropriate is the dynamic range of the camera?

Question 1: What is the dynamic range of the camera? It refers to the gray transition from white to black in the shot picture, commonly known as tolerance, which reflects the tolerance of the picture from white to black. The principle of dynamic range optimization is that the camera automatically reduces the brightness of the bright part, improves the brightness of the dark part, and prevents black light and white light. Its purpose is to make the highlights in a photo not exposed, and the details of the dark parts can be preserved, which is HDR technology; Usually, dynamic optimization can be set as a standard, and only scenes with dark parts and bright parts can be set as advanced.

Question 2: What is the dynamic range of a camera? Introduction to dynamic range:

1. Dynamic range was originally the concept of signal system. The dynamic range of a signal system is defined as the difference between the maximum undistorted level and the noise level. In practical application, logarithm and ratio are often used to represent the dynamic range of signal system. For a negative scanner, the dynamic range refers to the range in which the scanner can record the tone of the original, that is, the difference between the density value of the darkest point (Dmax) and the density value of the largest point (Dmin). For film and photosensitive elements, the dynamic range refers to the range from "darkest" to "brightest" contained in the image. The larger the dynamic range, the richer the levels that can be expressed and the wider the color space.

2. The larger the dynamic range of a digital camera, the richer the dark details and bright details that can be recorded at the same time. Note that the dynamic range is different from the tonal range.

3. When taking photos in JPEG format, the image processor of the digital camera will record the image information with a tone curve with strong difference between light and dark. In this process, the processor often omits some dark details and bright details on the original data. When shooting in RAW format, the dynamic range of the photosensitive element can be maintained, and users can compress the dynamic range and the tone range with appropriate tone curves, so as to output the photos to the display or print them out and obtain the appropriate dynamic range.

4. The photosensitive element of digital camera consists of millions of pixels, which absorb photons when the pixels are exposed, convert them into digital signals, and then image. This process is like collecting rainwater outdoors with millions of buckets. The brighter the photosensitive area, the more photons are collected. After exposure, the photosensitive element is given discontinuous values according to the different amount of photons collected by each pixel and converted into digital signals. The pixel values of not absorbing photons and absorbing photons to full load are shown as 0 and 255 respectively, indicating pure black and pure white.

Once these pixels are fully loaded, photons will overflow, resulting in the loss of information (details). Taking red as an example, the overflow of highlights makes the values of other pixels near the pixel full of red become 255, but their real values do not reach 255. In other words, the loss of picture details will lead to the loss of information in highlights. If we reduce the exposure time to prevent the overflow of highlights, many pixels used to describe the dim environment will not have enough time to receive the photon quantity, and the pixel value will be 0, which will lead to the lack of information in the dim part.

Question 3: What is the difference between the standard and advanced level of dynamic range optimization in SLR cameras? 1, dynamic range refers to the gray transition from white to black in the shot picture, commonly known as tolerance, which reflects the tolerance of the picture from white to black;

2. In the real environment with large light ratio (such as the cave scene in the sun), the tolerance of the camera can't correctly reflect this scene with large light ratio, so the dynamic range optimization is set, and some cameras are abbreviated as HDR；; ;

3. The principle of dynamic range optimization is that the camera automatically reduces the brightness of the bright part, improves the brightness of the dark part, and prevents black light and white light. Its purpose is to make the highlights in a photo not exposed, and the details of the dark parts can be preserved, which is HDR technology;

4. Dynamic optimization is inversely proportional to contrast. The higher the dynamic optimization setting, the lower the picture contrast. 5. In general, you can set the dynamic optimization as the standard, and set the dynamic optimization as the advanced level for the scenes with particularly dark parts and particularly bright parts.

Landlord reference.

Question 4: What does the dynamic range of the camera mean? For film and photosensitive elements, the dynamic range refers to the range from "darkest" to "brightest" contained in the image. The larger the dynamic range, the richer the layers that can be represented and the wider the color space. The larger the dynamic range of a digital camera, the richer the dark details and bright details that can be recorded at the same time.

Question 5: What is the latitude and dynamic range of a digital SLR? Latitude and dynamic range represent the range where a digital camera can record the brightness of an object correctly. Calculated by the difference between the brightest and darkest, and the unit is exposure value EV.

For example, the dynamic range of Canon 5D Mark III is 1 1.7 EV.

The dynamic range of digital camera is not fixed, it will change with the change of ISO. In other words, the dynamic range under unreasonable ISO value is different.

In fact, the tolerance and dynamic range of digital SLR are the same thing, but these two concepts come from different fields. The concept of tolerance comes from the range that photographic film can correctly record the brightness of an object in the silver salt camera era, which is expressed by the ratio or difference between the brightest and darkest.

The concept of dynamic range comes from the ratio or difference between the maximum undistorted output power of the circuit amplifier and the static noise power.

When the camera becomes digital, optical engineers and electronic engineers use their familiar concepts to understand the same thing. As we know, the digital camera first images on the optical sensor CMOS or CCD, and then amplifies the signal through the circuit. Strictly speaking, the tolerance should be reflected in the sensor and the dynamic range should be reflected in the amplifier circuit. In this way, the problem becomes more complicated. Consumers don't care about internal transformation, but only about the results, so manufacturers mix these two concepts together. The end result is that two concepts are one thing.

Question 6: What is the dynamic range of industrial cameras? What is a wide dynamic range? The unit of wide dynamics is DB. His algorithm is to divide the illumination of the strong light by the illumination of the weak light. For example, the maximum wide dynamic range of the human eye is 160DB, which means that the camera can see clearly on both sides when it agrees that the strong light of the picture is 160 times that of the weak light. The ultra-wide dynamic range camera can well adapt to the situation that the illumination intensity of different parts of the unified scene is quite different, and can dilute this illumination brightness difference in the final video, so that every part of the whole picture can be clearly distinguished.

Question 7: Please advise the photographer about the dynamic range! First of all, let's clarify two concepts: the dynamic range of digital camera and the dynamic range of image sensor, which are both different and related.

Digital camera can be regarded as a signal system, and its dynamic range can be divided into two parts: optical dynamic range and output dynamic range. Optical dynamic range = saturated exposure/noise exposure.

Among them, the saturation exposure refers to the exposure when the CCD reaches the saturation capacity of the potential well, that is, no matter how much exposure is increased, no more electrons can be accepted. Noise exposure is equivalent to the exposure when CCD only has its own dark current in all-black environment.

The output of digital camera is still in the form of digital quantity, so the dynamic range of output is mainly determined by the number of bits of A/D (analog/digital converter). The more bits, the larger the output dynamic range.

2. Definition of dynamic range of image sensor (taking CCD as an example): dynamic range (db) = 20*log (full charge capacity/dark current capacity), that is, the multiple relationship between the maximum accumulated charge and the minimum noise "charge".

3. We can see the difference between two concepts: one is the multiple relation of "exposure" and the other is the multiple relation of "charge".

4. Correlation between concepts: The (optical) dynamic range of a digital camera refers to the multiple relation of the corresponding exposure when its image sensor reaches the maximum accumulated charge and the minimum noise charge. Therefore, the optical dynamic range of digital cameras is mainly determined by image sensors such as CCD/CMOS.

5. Is the "photosensitive element area" the determinant of dynamic range?

When we pursue high resolution, the number of pixels of CCD increases, which leads to the decrease of the maximum charge that can be stored in the potential well and the decrease of dynamic range. This shows that the larger photosensitive element has the advantage of dynamic range. You can answer your first question like this: the area of the photosensitive element is one of the decisive factors, only one, not the only one.

Also, a digital camera has a larger photosensitive element, which means "more advanced", so its A/D bit number is higher, its output dynamic range is larger, and more high dynamic range technologies may be applied, so its overall performance is definitely better than that of a low-level digital camera.

Second, what other factors affect the dynamic range of digital cameras?

Besides the photosensitive element itself, the biggest influence factor is the application of "high dynamic range imaging technology", which is actually a general term, covering a variety of methods and technologies, such as:

1, multiple exposure image sequence. The original image is restored to the original high dynamic range scene through a specific superposition algorithm.

2. Beam separation. Using a specific optical path, the light corresponding to the sensor is split to obtain a group of images with different exposures, and then a high dynamic image is obtained by a specific algorithm.

3. Adaptive sensitive image sensor. The sensitivity of each pixel of the sensor can be controlled (by controlling the exposure time).

4. Spatial variable exposure pixel method. There are four kinds of pixels with different sensitivities in the pixel array, and the dynamic range is sampled while the pixel sensitivity changes in the spatial domain, so that the actual value of the current pixel can be estimated by using the information of adjacent pixels, and a high dynamic range image of the real scene can be obtained.

Answer the second question. The red Epic digital movie camera you mentioned, the size of the mysterious-X sensor is 30mm× 15mm,14 million pixels. It uses a high dynamic range image technology called "HDRx". Two independent video tracks collect images and then merge them, which is somewhat similar to the image sequence with multiple exposures. Due to the application of low pixels per inch and high dynamic range image technology, the dynamic range of red Epic exceeds that of Quan Huafu SLR.

Question 8: Why is the dynamic range of human eyes much larger than that of cameras? Personally, I think this question is false, because such a comparison is meaningless. If you really want to compare, compare the visual range of human eyes with the photosensitive range of photosensitive elements, or compare the "one-time viewing" of human eyes with a photo (this concept is made up by myself, so I put a quotation mark). What people see is dynamic, and the blue sky, white clouds, birds and flowers you see are all the results of comprehensive information in your brain after visual segmentation (the process is very fast, so you may just "see it at a glance" in your mind, but in fact your pupil, retina and brain quickly took pictures with different apertures+puzzles +HDR processing). If you stare at a scene with a large brightness contrast alone, you will find it difficult to get the details of the bright and dark parts at the same time without moving the focus of attention. In the process of moving the focus of attention, your pupil will change, which is equivalent to adjusting the aperture. In other words, the dynamic range of your "one-time viewing" does not include the complete "blue sky, white clouds, flowers and birds", and the picture you feel is post-processed. What is the dynamic range of people's "one-time viewing"? I forgot, I estimated it to be level 7, because photography was born from the beginning to simulate what people saw, and from the maturity of film technology to the digital age, our photo tolerance has been around level 7 (note that this is the final imaging result, not the dynamic range of photosensitive equipment). In fact, the dynamic range of electronic photosensitive elements is far more than 7 levels (in fact, black and white negatives also have 9 levels, but we often follow the principle of "three levels and four levels" when developing photos, taking 7 levels). It is not a problem to get the contrast above 10 level after taking pictures with raw. The question is: Does this picture look good? As mentioned above, photography was originally designed to simulate what the human eye sees, but isn't it a bit strange when you see those HDR-processed photos and sigh at their magnificence? Is that "true"? If you look at the panorama of Gao Fancha with naked eyes, can you see such exquisiteness? When many people use digital cameras for the first time, they will think that the photos taken by digital cameras are darker and grayer than those taken by film. Why? Because sometimes the light ratio of the scene we shoot is not so large and the camera's tolerance is too large, the picture we get is either white or black (human eyes+brain is also awesome, because seeing the picture with insufficient contrast can automatically improve the contrast, so untrained people sometimes don't realize that the contrast of the scene is low). . . Color reversal film is considered to be more suitable for taking scenery photos, because its tolerance is usually only 5 levels, so the picture contrast is greater. Another problem is that you can record more than ten levels, but you may not be able to display and print them (for example, the dark part of a photo looks dead black, but you drag it into ps and drag the color scale, and you pull out two details from the dark part. These two gears are already available, but the display can't present them). The second question, not to mention whether technology can do it (I think technology will definitely do it as long as there is demand, it is only a matter of time), how do you let the chip know how to divide the region to adjust the sensitivity? You tell it to "turn down the signal in that part of the sky", but it doesn't know God ... in the eyes of the photosensitive element, all the signals are the same. Then we can change the command mode and turn down the brightness above a certain value, right? This can be available for a long time, but it is mainly used in cameras. Probably because of the limitation of the performance of storage equipment in early years, all the signals captured by photosensitive elements can not be recorded, so they can only be pre-compressed in the machine. Broadcast cameras have very detailed menu settings. You can adjust the gradation curve nonlinearly according to different shooting requirements, just like adjusting the gradation and curve of a picture in ps, but this is decided in advance and executed by the camera processor when shooting. Digital camera files are not large, and all signals are stored and post-processed without pressure. However, nowadays digital cameras have the option of "photo style" with jpg compression, which is actually a partial adjustment.

Question 9: The purpose of improving the dynamic range imaging of dynamic range camera is to correctly represent the brightness in the real world from direct sunlight to the darkest shadow. The following techniques can improve the dynamic range of digital cameras. The technical name, function and technical points of improving the dynamic range of digital cameras Logarithmic response improves the dynamic range of imaging devices. Set logarithmic video amplification circuit. Deep trench technology improves the quantum efficiency of red light while maintaining the advantages of thin CCD. CCD is made of high-resistance silicon, and its thickness is about 40μ m. Double exposure improves the ability of imaging device to adapt to the change of target light intensity, and it is suitable for situations where light intensity changes sharply. Set the exposure of the sensor, and automatically adopt long exposure in weak light and short exposure in strong light.

Question 10: What is the tolerance and dynamic range of digital SLR? It is the camera's ability to record the brightest and darkest details and levels. In the same environment, the photos taken with the same shutter speed, ISO and aperture are rich in highlights and dark details, and the higher the tolerance.

Dynamic range represents the range from the brightest to the darkest of photos. The larger the dynamic range, the higher the tolerance, and the two are proportional. Light ratio is used to describe the contrast between light and dark in the shooting scene.