i solved this by adding max-width: inherit; into .lightbox .lb-image in easy-photo-album/css/lightbox.css and easy-photo-album/css/lightbox.min.css
the coding will looks like this
in easy-photo-album/css/lightbox.css
/* line 28, ../sass/lightbox.sass */
.lightbox .lb-image {
display: block;
max-width: inherit;
height: auto;
-webkit-border-radius: 3px;
-moz-border-radius: 3px;
-ms-border-radius: 3px;
-o-border-radius: 3px;
border-radius: 3px;
}
easy-photo-album/css/lightbox.min.css
lightbox .lb-image{display:block;max-width: inherit;height:auto;-webkit-border-radius:3px;-moz-border-radius:3px;-ms-border-radius:3px;-o-border-radius:3px;border-radius:3px;}
