Size of Thumbnails

For Masonry you typically control the following:

• The number of columns (you can configure it while building the gallery, after you have selected the layout)
• The minimum width of the column (via Photonic → Settings → Generic Options → Layouts → Masonry Layout – Minimum Column Width)
• The size of the actual image (you can set this via the “Tile size” option that comes up when you are building the gallery). If you have many images on a page, use this option to pull mid-sized images so that you your page loads up faster and still looks good.

You haven’t provided a URL here, o I am assuming that you are referring to the link you posted here. What you are seeing is not a “slider” – it is a justified grid layout. If you add 1-2 more photos, you are likely to get those two in the same row too. But if you add 5 more, they are likely to go to the next row… but the gallery will occupy the full width.

Basically the Justified Grid has only one objective – to make sure that you gallery occupies 100% of your page width, regardless of the number of thumbnails in it, and regardless of the size of the thumbnails.

To that end, you might want to consider a different layout, e.g. a square thumbnails layout. See examples of different layouts here.

I am still unsure of your requirement, but you might want to try the option to “Show whitespace to the side for narrower images”

You cannot define a fixed height for the LightSlider script. If you wish you can set an attribute like columns=4 for the slideshow – that will show 4 images in the same line and the height will be a lot less.