I replaced my NIKON P90 for interior work photos with a D5500 for better light control without flash. That is working fine but when I resize for the Web my photos are 500 x 334 instead of 500 x 375 which my website is set up to accept. Why?
The sensor ratio are different:
When resizing your images, you are probably fixing the length of the longest dimension of your image to 500 pixels, and the shortest dimension is computed accordingly.
You need to crop the D5500 images using a 4/3 image ratio.