Hi All,
I'm now getting quite a lot of interest in doing illustrated books. I've searched the forums and couldn't find any threads on this topic, please forgive me if there is, I simply didn't see it.
Trying to be all things to all persons (PC or what?

), or, in other words, all things to all flavours of ebook readers (hardware that is), is there an optimal size, resolution and format, I can make my illustrations using photoshop? The format would probably be PNG, but I'm open to other suggestions.
I guess on an iPad it would be better to get the highest possible resolution for, say, a technical illustration so it can be enlarged for the reader to study and keep it legible. But on a run-of-the-mill image of a portrait or a landscape, where the image is just to enhance the text where it doesn't need to be enlarged and the end-user screen is the limiting factor.
I'm trying to be as economical as possible with file sizes at reasonable proportions. The illustrations will be in colour.
Thanks in advance,
John.