Serious noise problem of Nikon SLR camera shooting in indoor light

1. Noise caused by camera hardware such as image sensor. The noise is mainly caused by the noise of electronic devices and amplification circuits used by the camera and the interference between electrodes of the image sensor. For example, in the case of the same number of images, the smaller the CCD area, the smaller the pixel points and the denser the electrode spacing, the greater the photoelectric interference between them and the more noise.

2. Noise caused by overheating. When used at high temperature or for a long time, the image sensor may become hot, which will affect the performance of CCD and electronic components and produce white, red or green "hot pixel" noise. In addition, long-term exposure will not only make CCD heat up and increase noise, but also cause some specific pixels to get out of control and form more noise because it can't handle the huge workload caused by the slow shutter speed.

3. Noise caused by high ISO. High sensitivity is generally in the case of low light illumination, CCD unit can not sense enough light, and it depends on the gain of electronic circuit to enhance the signal, and at the same time it will increase noise.

4. Noise generated by using telephoto. When shooting with telephoto, the noise generated by the lens itself will be amplified when the scene is enlarged, especially when using digital zoom, some pixel mixed noise will be added.

Noise generated by 5.JPEG format. Most DCs use JPEG format to compress images and then store the output, which is a kind of lossy compression. For example, if it is processed in units of 8×8 pixels, it will be unnaturally combined with the next 8×8 pixel unit edge at its edge position, thus generating mosaic noise.

Second, several methods to reduce noise

1. Use a digital SLR camera. The image sensor of SLR camera is much larger than that of portable DC, and each pixel is larger, and the image noise is obviously less than that of portable DC. In the circuit design of SLR camera, various electromagnetic isolation technologies are adopted, which can effectively control the interference between electrical components, and the noise control is far better than ordinary DC. In addition, SLR cameras can output images in RAW format, which can avoid the noise caused by JPEG lossy compression. For ordinary users who buy portable cameras, the noise inherent in the camera hardware is uncontrollable. When buying, we should pay attention to choosing a large CCD camera under the same pixel requirements.

2. reduce ISO. In the case of insufficient light, many people choose higher Is0 sensitivity in order to improve the shutter speed and avoid jitter and blur when shooting manually. However, high IS0 is easy to produce noise, and generally there will be obvious noise above IS0 400. Get into the habit of shooting with a tripod and reduce noise. In addition, if Is0 is set to "Auto" gear, the sensitivity will increase automatically in the case of poor light, so remember to set it around 100.

3. Use the "correct exposure" method. First of all, try to shoot in good lighting conditions, or make up the light appropriately to avoid high IS0 and long exposure. Secondly, we can deliberately overexpose by exposure compensation when taking pictures, that is, the color levels of the histogram are distributed to the right as far as possible, and of course, we must ensure that it cannot be overexposed, so as to reduce the brightness of photos and the noise level in post-processing. The "exposure to the right" method is more suitable for RAW format. Through the brightness and contrast adjustment function of RAW processing software, the histogram of photos that look "too bright" is adjusted to the normal state in the middle, which weakens the unsmooth problem and possible noise in the dark part of photos.

4. Don't turn on the camera for a long time. Try to avoid using digital cameras in strong sunlight and high temperature environment, and do a good job of "heatstroke prevention and cooling" when using them in high temperature environment such as summer. It can be properly turned off during the shooting process to reduce the temperature rise caused by long-term start-up shooting. In addition, the strong magnetic field environment will also increase the noise of photos, and DC should be avoided near high-voltage lines and substations.

5. Turn on the built-in noise reduction function of the camera. Some DCs provide a built-in noise reduction function mode, which can be turned on by menu selection. However, these built-in noise reductions are usually realized by software, which will also cause the loss of details while reducing noise.