Today I was shooting in aperture priority mode (trying to get more practice) outside. I was looking in my viewfinder to make sure that I was not overexposing due to light. Keep in mind that I was in the shade and the sun was setting. The picture looked clear in my viewfinder, but when I uploaded them for pp I noticed a very grainy appearance. I am not sure what I did. Can anyone help? Thank you so much for your help.