What Should I Consider When Buying a Digital Camera?

In a digital camera, ISO refers to the speed of light received by a CCD or CMOS sensor. The higher the ISO value, the stronger the photosensitivity of the photosensitive component. The calculation formula of ISO is H * S = 0.8 (S sensitivity, H is the exposure amount). From the formula, we can see that the higher the sensitivity, the less the requirement for the exposure amount. Deformation formula: H = 0.8 / s, under the premise of the same exposure, the exposure time at iso50 is twice the exposure time at iso100. Commonly used ISO values are 50, 100, 200, 400, 1000, etc. iso50 and iso100 are used when the light is sufficient, while high iso values are used when the light is insufficient.

ISO in digital cameras

In general, the lower the iso value, the higher the quality of the photo, and the more delicate the details of the photo, the higher the iso value, the higher the brightness of the photo, and the quality of the photo will decrease as the iso value increases. ,

The high and low ISO sensitivity means that at the same EV exposure value, a higher ISO sensitivity is selected, and the same exposure can be obtained with a faster shutter speed without changing the aperture. Conversely, it is possible to use a smaller aperture while maintaining the correct shutter exposure. Therefore, when shooting under relatively dim light, you can often choose a higher ISO sensitivity. Of course, for SLR cameras, you can also choose to use a larger diameter lens to improve light flux. For general digital cameras, because they use fixed lenses, they can only adapt to shooting under dim light by increasing the ISO sensitivity, especially when auxiliary light cannot be used. ^[1]

The film used in the traditional camera is to increase the sensitivity of the film by controlling the difference in the sensitivity of the dye to light. However, an increase in sensitivity will reduce image sharpness and increase contrast, that is, reduce dynamic range. The digital camera s photo sensor is an active device. There is dark current. The cut-off current is set in normal mode and the part with noise interference is not used. The high-sensitivity mode uses the part with high noise. These background noise reflect On the image is random noise. As long as the sensor is not improved and the aperture is not changed, there can be no real improvement in this problem. At most, the algorithm can be used to weaken the intuitive feeling of noise. This is why high-iso cameras often have larger lenses and larger sensor sizes.

Therefore, when the scene lighting conditions are not good, the application of auxiliary light (flash and reflector) should be considered first, and the use of tripod and anti-shake should be considered when auxiliary light cannot be used, and then the method of improving ISO sensitivity should be considered.

For places where the lighting is often dark such as shooting on stage, and the use of flash or inconvenient tripod is not allowed, you can choose a digital camera with a larger lens diameter, a shorter focal length, and a larger ccd size. To shoot (of course, a large aperture will also reduce the depth of field).

Night scenes often use larger apertures and longer exposure times. If you choose a higher ISO speed, noise and noise will inevitably occur. At this time, you can use a tripod and a self-timer. It is possible to use a shutter release again. Selecting a lower ISO speed can avoid noise and noise.

Therefore, when buying a digital camera, you need to consider choosing a camera with the largest iso and a larger size ccd, which is more conducive to shooting in low light conditions. Whenever possible, use auxiliary light sources and longer exposure times.