rcmarple has it right.
The Apple techies came back to me to-day.
There is software in Itunes that detects which ipad you are attaching, and when it syncs the ipad 2 it compresses the files of photos as they go over. (That bit of info I have not heard before - It's not in the Handbook)
With the ipad air as the screen is allegedly so much better, it does not compress the files.
The Apple techies say there is no way of doing this compressing for an ipad air. (Other than doing it on my pc using someone else's software before the files are sync'd)
So any high-quality photo will take up much more space on an ipad air than it will on the ipad 2.
I wish I had known that when I bought an ipad air 32 gb. That will not even take my photos, let alone anything else. Apple will NOT allow me to "upgrade" my new machine to a 64gb one.
A very expensive mistake made by me, caused, in my opinion, by a lack of clarity in apple marketting.
Mind, they are unlikely to flog something with the strapline "Takes less than half the number of photos compared to our old model"
My cheap and cheerful android tablet will take all my photos with no compression as it has a micro-sd card slot.