[iMore Question]

my mac book air has too many photos but when I delete them they were deleted from my desktop iMac

[Just_Me_D]

I'm going to assume your photos are synced via iCloud. Having said that, if you disable iCloud Photo Library and/or Photostream on your MacBook Air, you will be able to manipulate the photos on it without interfering with the ones synced to your iMac.

[Bazza1]

...or do what I do - when I (finally) moved to Mac from Windows, I simply moved my entire Photos folder over into my User profile (an alias on the Desktop). Inside this folder are sub-folders I had already created by year and / or event. To view and do most pic manipulation, I use Preview, but if I do use iPhoto / Photos, I export the pics directly out again.

Insofar as the Photo folder is standalone (and not part of an Apple app), I can do whatever I like with photos on my Mac and not have iCloud screw with them. Meanwhile, I can pick and choose within iTunes what Photo folders I wish to include on my iPhone and they show up there as expected.