A tour operator or destination site is a catalogue of large images: destination cards, itinerary day-by-day photos, hotel thumbnails, tour galleries, and a hero that rotates on the homepage. Those files usually come from stock libraries or a photographer at full resolution, and each destination page adds another ten to thirty of them. The pages that convert best — itinerary and pricing — are often the slowest, because every day of the trip carries its own photo gallery. Reduce each image to the size its card and hero actually render at and the catalogue gets lighter without losing the imagery doing the selling.