Originally Posted by marbs
This allows the image to be as large as the space provided, but no larger. I don't see any CSS in the free Economist, so I would expect the image to be full size, if it fits, not scaled up. However, if the OP has a default device set, the recipe will create images scaled for the screen size of that device. If he then views it on his computer - the image may have been sampled down for the device when the recipe EPUb was created, then scaled up when viewed on a larger computer screen. What device is set for the default? What device is he viewing the recipe on?
will produce smaller images, but he might be losing resolution due to the default device he's told Calibre he's using. (There may also be some internal style that's not getting stripped that may override some of this.)