Hi @hannekedebruin
There are a few things to do:
1) Upload images with higher resolution – I noticed that one or more images in the gallery was smaller than the thumb size that you had set for the gallery. This will cause the images to upscale in the browser which will make them look blurry. Always make sure the images width is bigger than the width set on your masonry gallery.
2) Goto FooGallery Settings and under Images Tab, set the image quality to 100. the default is 80.
3) For retina devices, make sure you have set your galleries to use 2x retina images. This will still not help if your original images are small, but it will help for the other images with larger resolutions.
