Today's cameras capture increasingly large resolution and can generate files many gigabytes in size. Unless you are printing billboards or have a very specialized application, ultra-high resolution is not meaningful.
dotPhoto stores images up to 6000 dots (or pixels) on a single side. When the longest side is 6000, the other side is calculated to have the same number of pixels per inch; in other words, the other side is proportional to the longest side. Any image of 6000 dots on a side is large enough to make a high-quality print of any product printed at dotPhoto. If an image is larger than 6000 dots on a side, it will be reduced to 6000 on the longest side and proportionately on the shortest side.
A 6000 x 6000 dot image is 36 million dots or 36 megapixels.
The largest upload allowed is 20 megabytes per file, which is a huge file -- especially for a JPG. Since we recommend no more than 1000 photos per upload, the largest group of photos to upload would be about 20,000 MB or 20 GB.