For the family album, I’ve been exporting my photos in Darktable to JPEG (8-bit) format at 90% quality. The images are organized into albums online using Nextcloud. But I’m reaching the limits of my available storage space. Typically, each *.jpg export creates a file ranging from about 20MB to 38MB. I haven’t paid much attention to this before, but I now realize that’s a lot. It quickly adds up to a few GB. If I reduce the quality to 85%, the files are just under 25% of the size compared to the 90% quality export. At least on the web, I don’t see any difference at first glance.

Since some family members occasionally create a photo book from the pictures, I’m not sure how the quality will hold up in print. I won’t know for sure until it’s too late. But if I can’t tell the difference at 100% zoom, I’m hoping the print quality will be at least acceptably similar.

According to Google Page Speed Insights, it’s recommended to use WebP with a quality of 80%. The resulting files are now only 20% as large as the 90% JPEG exports. I notice slight differences, especially with smooth color gradients, bokeh, and similar elements. There are subtle variations and color shifts, but hardly any artifacts. If I don’t know the original, it doesn’t stand out. But it does in a direct comparison. I can’t estimate how this will affect the print as a photo book. What I do see, however, is a significantly longer export time.

Question for the community: What would you recommend? Stick with 8-bit JPEG and set the quality to just 85% (or less), or switch to WebP with 80% quality? Maybe you have another or better idea?

BTW: One additional question. Pixel dimensions of the photos are usually huge in my case. I don't scale down the pictures during export, because i don't know how to do that. Some photos are landscape, some portrait, some are cropped, some not. So every photo can have a other resolution. What should i use to have a max resolution of 2560x1440 Pixel and keep the aspect ratio of landscape and portrait and cropped images. I don't want to upscale images, only downscale, when they are bigger as the max resolution. I don't understand the documentation of the setting.