Does it take upwards of 5 minutes every time? In general when you first add an image to the field, when the entry is submitted, Ansel has to process it. If the images are very large this could take a little bit of time. If it's only taking that long when you first add image and submit the entry, that's probably it, though 5 minutes certainly sounds excessive. It's shouldn't take more than 10 to 20 seconds unless we're talking about a very large number of images.