Compared to the X20, the X21's camera configuration has not been significantly improved, but vivo still regards the camera as an important selling point, and the X21 uses an improved image algorithm. The official saying is that there is some big improvement.
There are multiple versions of the X21. We have this under-screen fingerprint scanner version, which is based on the Qualcomm Snapdragon 660 AIE processor, the standard version is also based on this platform. There are no differences in the camera configuration and algorithm between these two versions, so the standard and the UD version have no difference in imaging. Recently, there is one more version based on MediaTek P60. The camera configuration is said to be the same, but the change of the basic platform may cause the algorithm to change. Therefore, its imaging may not be the same as the standard/UD version.
The X21 uses a dual camera design. Unlike the X20, the camera's horizontal rows become vertical. The main lens aperture is F1.8 with about 26 mm equivalent focal length, but the EXIF recorded as 30 mm, it should be a mistake. The main lens sensor has two modes, one is 12MP + duel-pixel focus, the other is 24MP + phase focus. There is few public data for this image sensor, it should be the same with that on X20, coming from Samsung. The secondary lens does not participate in imaging, does not provide extra focal length or mono mode, it can only be used as depth of field detection.
In the 12MP mode, a full-pixel dual-core focusing system will be activated, and its focusing speed can reach the current best level. With the support of the pre-focus system, it will refocus in time if there is a slight scene change. At 24MP mode, the normal PD focusing mode is activated, and the focusing speed is slower than that of the dual-core focusing. Actually, in most shooting scenes, such as scenery, still life, visitors, etc., no obvious focus speed will be felt.
The biggest improvement compared to the X20 is that the optimized focus logic. The X20's AF detecting area is in the center of the screen. When the subject is not in the center, it is easy to focus to the background. The X21's AF detecting area is much larger, so the previous problem was solved, which significantly improved the focusing experience. The logic for macro focus is also optimized, and shooting macros is easier.
The X21 default metering mode is the center weighted average. In most scenes, the metering result is good, the metering is aggressive under strong light, and white objects may easily overflow. This is a problem that has been troubled for several generations and has not been solved. Radical metering can lose the details of the highlight area, negatively affecting the overall resolving power. Under low-light scenes, it is better. The X21 can also metering on touch spot, the sensitivity is controlled based on the scene light difference, which is usually low and easy to grasp.
Exposure compensation tools are provided in both automatic mode and professional mode, but the control mode is not uniform. Exposure compensation range is 2EV with 0.3EV stop. X21 also provides histogram tools in professional mode, which is very useful for photographing, precise exposure control.
X21 is optimized for backlighting portraits. vivo calls it "backlit and clear". Even with poor light conditions, priority is given to correct face metering, and then HDR is used to ensure that the background is visible. As shown in this photo, the face in this image is not dark, and even stays ruddy. In this particular skill aspect, the X21 is better than any of Samsung or Apple phones.