A3 In Photoshop. Photoshop resamples images using an interpolation method to assign color values to any new pixels based on the color values of existing pixels. In the Preset section select International Paper.
Make sure that your resolution is at least 150 dpi which should correspond to 1754 x 2480 pixels. The details of the preset appear in the Preset Details panel along the right of the dialog box. The typical A4 print size is a good dimension to use for.
Name it A3 and enter the dimensions for A3 paper save it and it should be added to the list.
Equivalent A3 paper dimensions in pixels at 300 DPI and 72 DPI respectively are. Just open dont try to drag it into anew document new file. If I wanted the height to be exactly 4 inches I could change the Height value to 4 inches which would then change the Width to 6001 inches. In the Artboards To Files dialog do the following.