Better image in 'before' mode

Hi,

I have just noticed that when I press the backslash key to see the unedited image, the image I see is much sharper than the image when I don't press the key. I have not done any editing in LR, just imported the photo. I am attaching the example with the photo on the right the cleaner image that shows when I have pressed the backslash key and the image on the left the version LR has produce before any editing.

I'd liek to understand why this is and whether I can import the images to ensure they stay as sharp and crisp as the image I see when pressing the backslash key.

Any help would be great.

Many thnaks.