The Gallery uses the same image for the thumbnail and the larger gallery image. I’m shrinking my images, so what is the optimal size I should make them?
Great question.
Elements is designed to be flexible with image sizes, but for best results in galleries, we recommend using images that are at least 1200px wide for modern displays. This ensures your gallery looks sharp on all devices.
If you want to optimize for even faster loading, you can use slightly smaller images.
Hope that helps.