After months of attempting to figure out what was wrong with my blurry blog header image, Judy Perez of Painted Threads pointed me in the right direction. I had searched for the answer online extensively, and no one had ever written about this, so I’m doing it now.
Supplying your own blog image header requires that you crop your image to the correct size of your blog header. In my case, that was 950×200 pixels. I cropped image after image in Photoshop Elements, only to have the image become horribly blurry. I tried to improve the resolution, to sharpen it, and nothing worked.
Here’s the secret: You can’t use an image that was photographed at too low a resolution in the first place. You must take a photo intended for a blog header at a higher resolution than normal, since the pixel width required for a blog header image is wider. My photos taken at the 3:2 resolution setting didn’t have enough pixels to show the detail necessary when I cropped them. So I changed the setting on my camera to use a higher image size (5M) which contains a higher number of pixels. I could then crop the image and the detail was much better, with no more blur.
Note to Mac users: I use iPhoto to upload my photos, as I find it infinitely simpler than Photoshop Elements, but iPhoto does something to the image size to make it smaller so it can easily display large numbers of photos. When I open the image in Photoshop Elements, it says the photo is only 72dpi. I double the resolution, to 144, which improves it greatly and allows me to crop the image with no blur. There may be a slicker way to do this, but this worked for me and hopefully it will help you too.