Charles W Davis said:
If you want it to fill the screen, open the image in a photo editor
and crop the image to the 16:9 proportions. Just hope that nothing of
importance is lost.
The ratio of the JPEG output from most digital cameras is 4:3.
Consequently, the original JPEG file will be a perfect fit for the 4:3
screen of your desktop computer - but not for your 16:9 laptop.
When you (or a photo lab) produces a 4" x 6" print from your memory
card, the printer crops the original image to fit the paper. With a 6"
x 4" print, you will lose a significant "slice" from the top and bottom
of the picture. (A 5" x 7" print is better fit.)
However, print size is irrelevant, when you create a wallpaper for your
computer, because you should always use the original JPEG file from the
camera to create the wallpaper.
Depending upon the settings, the typical maximum JPEG output from
digital cameras might be:
3 megapixel camera 2048 x 1536 pixels
5 megapixel camera 2592 x 1944 pixels
Pixel density of the original JPEG file should be adequate to produce
good quality wallpaper on either of your computers. Conversely, a
scanned image of a 6" x 4" print would probably produce disappointing
results.
Upon the assumption that you are using the original JPEG file (as
opposed to a scanned copy of a printed photograph), you will need to
change the ratio from 4:3 to 16:9, before you use the photograph as a
desktop wallpaper for your laptop computer. There are two possible
solutions.
The first solution involves the use of a photo editing program to crop
the original JPEG image. (Save the cropped image with a different file
name). However, you will lose a significant part of the picture, when
you crop the original image.
A better solution also requires the use of a photo editing program.
This time, you leave the image size unchanged - and increase the canvas
size to the required ratio.
Adobe Photoshop Elements provides a suitable tool. (Firstly, open the
JPEG file and change the background color of the image to black. Then,
click on Image | Resize | Canvas Size. Save the edited image with a
different file name). Then, the wallpaper on your 16:9 display will
show black bars at either side of the picture.
I am sure many other photo editing programs offer similar options.