Image blurry

I've been working on a short video for a class I'm in, but the images I upload come out blurry in the end. The photos themselves look good when just pulled up on my computer and when in my source tab. When I place the image in the timeline it zooms in, and when I go to correct that the image resolution is destroyed. I've also noticed when I place a transition from the pervious image to this one the image looks great but only while the transition in happening (see images below). Does anyone know how to fix this I've tried messing with the sharpen, unsharpen mask effects, changing the resoution and the picture types but to no avail? Any and all ideas are appreciated.