quick bit of help

[lukese]

hi all girlfriend has found a new hobby in photography, her main target being our new baby boy, some of the shots are really good, amazing in fact, she just did a quick two day course that was basicly learning how to take the camera of auto and get the most out of it and her photos have come on loads, she said the guy mentioned on teh course about buying a 50mm fixed lens for portrait shots, i have bought one of these today, but when we put it on the camera it doesnt take any shots, just flashes on the screen F--, now im wondering if i have bought her the right lens!

the camera is the following

Pentax K-R
http://www.jessops.com/online.store/...9386/show.html

and the lens i bought was a

http://www.jessops.com/online.store/products/15485/show.html

should they be compatible and if so whats going on and why wont it let her take photos?

any ideas would be greatfull

thanks people!

[lukese]

google paned out in the end had to set camera to “Using aperture ring” setting to “Permitted”

coolio