Archive on time machine?

I have an external drive which backs up my macbook regularly with time machine. The problem is my macbook is fast running out of space - mostly being taking up by my growing iphoto images.


To be honest, I don't think I fully understand how Time Machine works. I like that it backs up my drive, but what if I was to delete, for example, some of my photos to save space on my macbook but still keep them on my time machine drive. Is this possible? What I'm asking is, is it possible to archive on a time machine drive and delete from my macbook?

 

oh.
So what do people do in a similar situation? So, I need a second external drive to archive some of my data. And I suppose this will also need to be backed up on a time machine drive...... This is really doing my head in.

Thanks for the reply.