How do I round all images except for header logo?

I am using this code to round all images on my website (blog images, summary blocks etc) but I don't want it to apply to my header logo. Is there a way to do this with css? 

img {
    border-radius: 20px!important; 
} 

Use this code instead

article img, footer.sections img {
    border-radius: 20px!important; 
}