We recommend that if at all possible Auctiva users upload images that are 1024 pixels by 768 pixels or less and avoid larger image sizes.
The largest image size that we store on our image hosting servers is 1024 X 768 pixels. When images are uploaded on our service that are larger, the servers automatically perform a software compression to crunch these big images down to the 1024 X 768 size. Since 1024 X 768 is the largest image you can store, there is no real point to uploading an image that is larger than 1024 x 768.
The big benefit to you though is that your image quality as seen in your listings will be better if you can avoid doing as much 'resizing' of images as possible before you upload it.
Most digital cameras have settings that allow you to specify how big the images will be. The settings vary by manufacture but may be something like 'JPEG-small' 'JPEG-medium' or 'JPEG-Fine'. Some digital cameras have even more size options and may label them differently.
If when you take the pictures for your listings you avoid the larger sizes your camera is capable of, you will get images that require less resizing after the fact...maybe even none..prior to your uploading them.