How to set src from SourceSet?

[mittererr]

Is it possible to ser src from a Sourceset. My problem is, the lightbox image is as small as the preview image in the slider. With other words: for lighbox it is necessary to take an other image out of the sourceset.

576w ist choosen by the browser. For light box I want to show width 768 or 992.

<picture data-alt="Dorfbahn Königsleiten" title="Dorfbahn Königsleiten" data-default-src="/imagebilder/winter/image-thumb__11__contentimage/arena_2015_139.jpeg">
    <source srcset="/imagebilder/winter/image-thumb__11__contentimage/arena_2015_139~-~576w.jpeg 1x, /imagebilder/winter/image-thumb__11__contentimage/arena_2015_139~-~576w@2x.jpeg 2x" media="(max-width: 576px)">
    <source srcset="/imagebilder/winter/image-thumb__11__contentimage/arena_2015_139~-~768w.jpeg 1x, /imagebilder/winter/image-thumb__11__contentimage/arena_2015_139~-~768w@2x.jpeg 2x" media="(max-width: 768px)">
    <source srcset="/imagebilder/winter/image-thumb__11__contentimage/arena_2015_139~-~992w.jpeg 1x, /imagebilder/winter/image-thumb__11__contentimage/arena_2015_139~-~992w@2x.jpeg 2x" media="(max-width: 992px)">
    <source srcset="/imagebilder/winter/image-thumb__11__contentimage/arena_2015_139~-~1200w.jpeg 1x, /imagebilder/winter/image-thumb__11__contentimage/arena_2015_139~-~1200w@2x.jpeg 2x" media="(max-width: 1200px)">
    <source srcset="/imagebilder/winter/image-thumb__11__contentimage/arena_2015_139.jpeg 1x, /imagebilder/winter/image-thumb__11__contentimage/arena_2015_139@2x.jpeg 2x">
    <img alt="Dorfbahn Königsleiten" title="Dorfbahn Königsleiten" src="/imagebilder/winter/image-thumb__11__contentimage/arena_2015_139~-~576w.jpeg">
</picture>

[mreq]

You can set any src you want, see the options https://github.com/mreq/slick-lightbox#options. For support, ask over at Stack Overflow.