pede wrote:If you click on a photo, it will be displayed in large size including the caption.However, the description of the picture is hidden after a short time. Only when you move the mouse, the caption appears again.
This is how it's supposed to work. Visitors may want to view the image without having distracting captions always overlaying images. The captions are visible as soon as user moves the mouse, so normally a visitor would just move mouse slightly if they want to read the caption. Furthermore, visitor can move mouse OVER the caption, causing the caption to remain locked on screen without disappearing ... You would think that should be sufficient for a user to control caption visibility. If you really need to "lock" captions to always be visible, you can disable Settings > Popup > Popup Caption > Autohide caption.
Also, just FYI, on touch/mobile devices, the caption will be visible/hidden on tap, so the user can decide if they want to have captions visible or hidden while they navigate/swipe.
pede wrote:Is it possible to change the time span of the caption or display the description permanently?
Unfortunately no. It's set to 3 seconds, which should be sufficient time for the visitor to either hover the caption to lock it, or allow it to disappear giving optimal view of the image.
pede wrote:Is it possible to start a slide show with that 'subtitles' in this mode ?
Sorry, I'm not quite sure what you mean "'subtitles' in this mode". In next X3 release, we will be including a "play" button, which will allow the popup to autoplay through slides at a set interval.