Dear  martinmalone ,

 

That image's style is controled by  "LightBoxFrame ZINDEXLIGHTBOXFRAME"  and "LightBoxMask ZINDEXLIGHTBOXMASK",

<div class="LightBoxFrame ZINDEXLIGHTBOXFRAME" style="position: absolute; top: 205px; left: 410px; width: 504px; height: 360px;">
<div style="position: absolute; top: 0px; left: 0px; width: 1324px; height: 602px;" class="LightBoxMask ZINDEXLIGHTBOXMASK"/>

 

You can visit our online demo, when you click any image or you upload a new image  and click that new image, it is always center.   Your own style has an impact on DotNetGallery and promotes this issue.  When click image in your site, it will create one horizontal scroll bar, the width of that scroolbar is not fixed, sometime, it is over 2000px, please  check your style.

Keep us posted.

 

Regards,

Eric