I am a novice. Please help me to explain several problems in cross focusing of SLR cameras. How to distinguish them?

Focus sensors are arranged in a horizontal row, which is called "straight line" (vertical row is also possible, but rarely); Horizontal row and vertical row, isn't it "horizontal"? Horizontal rows are mainly used to identify vertical lines like fences (this is called "horizontal resolution" in jargon). When the camera shoots vertically, this sensor is not easy to identify, so isn't the "cross" horizontal and vertical?

The focus is on the distance sensor of the camera, which is divided into horizontal and vertical directions. Generally, the accuracy in the horizontal direction is high, that is, the sensitivity or accuracy is relatively high. The main focus of high-end machines is cross, only some middle and low-end machines are cross, or only the central focus is cross. Evaluating the level of focusing system mainly depends on the accuracy of this sensor. Because the larger the aperture, the larger and brighter the luminous flux and the higher the focusing accuracy, so the sensitivity of 2.8 is better than that of 5.6, and the cross is better than that of one direction. The cross is also divided into horizontal 2.8 and vertical 5.6; Both 2.8, double cross. The so-called sensitivity of 2.8 actually means that the sensor has the highest accuracy when the lens is unchanged at 2.8 or the maximum aperture is greater than 2.8. Because Canon's camera has the aperture set by the body, no matter how large the aperture you actually use, the camera always uses the maximum aperture when focusing.

One of the most basic factors that determine the grade of a camera is the accuracy of the focusing system, the other is the photometric system, followed by other pixels and high ISO.