Still pictures blurry in FCP

I'm having a similar problem to other discussions I've seen on here, I just can't find the correct solution for me.

My still pictures are coming out blurry. It may look great in the viewer but in the canvas it looks blurry. This is not the case with all still pictures, just some. It doesn't help to export the final video out to QuickTime and view it on a tv or computer. (I've read some formus that say that fixed their problem.) I'm assuming it's the issue of the canvas/sequence has a lower resolution than the picture that's coming out blurry. But how can I fix that problem? Is there a something I can change in the sequence settings to make it look like it's supposed to? And if I do change the settings will that mess with anything else in my sequence? (I mean the video as a whole- there is video, still, pictures, effects, etc on the sequence.) Also, I do not have Photoshop to mess with the picture.

Oh and yes, I've rendered my face off so that isn't the problem either. 🙂

Thanks so much in advance!