What is the reason why the display image of Haikang screen becomes larger?

This may be a mistake. You can try the following steps:

1. First open Hikvision iVMS-4200 client and log in.

2. Click the main preview.

3. Click the small icon in the lower right corner.

4. Click Edit in the pop-up window.

5. Click Add in the red circle and enter the scheme name.

6. You can choose the default cutting size in the red circle, such as 3*3. The fewer grids, the larger the grid.

7. If there are many cameras, it is best to choose 6*6.

8. Use the mouse to pull in the small grid and occupy four boxes at the same time, and then click Merge to merge the four small grids into a large grid to display the picture to be monitored.

9. When you look at the big grid carefully, the cross of the grid has been thinned or turned into a dotted line, indicating that the merger is successful.

10. If the merge is wrong, you can also cancel the merge.