No. Even if you upload big images to Story Chief, the app will resize it to fit the different mediums without cropping or magnifying (this way you would lose quality). Also, the weight (mb>kb) will be reduced automatically.
If the picture is large enough, you can even choose another size (larger or fullscreen).
If you use Story Chief to collaborate on offline articles, make sure to upload images of 300 dpi.
When you're in a story, click on the 3 dots at the right top side, and then on 'download'. You can export the story to Word or PDF and download images (so also in 300 dpi) in a ZIP-file and send it to your designer(s).