How do I make pictures larger on command

[Crystal]

I have several pictures on each slide how can I select them during the slide
show and enlarge them? the emphasis in custom along with the grow and shrink
is not working. The picture is grainy when you do this

 

[PPTMagician]

See the section on Zoom in this article:
http://office.microsoft.com/en-us/powerpoint/HA102326311033.aspx?pid=CH100673421033