Header image is distorted

I’m having an issue with getting my header image to appear properly.

I’ve had this same problem using two different premium Studio Press child themes (Generate and Streamline) as well with Twenty Ten and Twenty Eleven.

I have a 433 x 122 .png header image. I’ve uploaded the image via the header tab. On the next screen, the crop window at it’s largest size removes most of the image. The image that appears on the header when I view the site is incomplete, and the small piece of the image that does appear on screen is blown up to several times the size of the partial image. I’ve tried a few other similarly sized images with the same result.

Strangely enough, if I upload the same exact images to a Canvas child theme, the images appear on the site header perfectly fine.

Is there is a particular image format or size that I should be using? What am I doing wrong? Is there some other way of inserting the image into the theme that won’t cause this problem? I’m not really that familiar with coding, but does the coding need to be changed? Is something else causing this?

I’ve been spending a ton of time trying to figure this out, and I keep telling myself this shouldn’t be so complicated. I thought I could just upload easily and move on, but this has been very frustrating.

I could really use some help to get this fixed!! Thank you.