When you add a still image, you can assign a specific duration to it. The duration specifies how much time the image occupies in the Quick view/Expert view timeline. You can set a default duration for all still images that you add, and you can change their duration in the Quick view/Expert view timeline.
The frame rate of your project determines the amount of time that a certain number of frames occupies. If you specify 30 frames for a 29.97 frame‑per‑second (fps) NTSC project, each still image has a duration of about one second. For PAL, if you specify 25 frames for a 25-fps project, each still image in the Quick view/Expert view timeline has a duration of one second.
Changing the default duration of still images does not affect the duration of still images already in the Quick view/Expert view timeline or Project Assets panel. To apply the new default length to all still images in your project, delete them from the Project Assets panel and reimport them into your project.