Photoshop image size vs Bridge

Question

A very basic question that I've not been able to find the answer to. My Raw images come up in Bridge at around 20-25 MB, 16 bit. When I open them in Photoshop they all seem to have identical Pixel sizes at 120.3 M and 5616 x 3744 pixels (ie total 21 MPixels) even when my images in Bridge are all slightly different sizes depending on content. What exactly is the 120.3 M if it isn't Bytes or Pixels and why is it constant for a particular camera? It obviously relates to bits and bytes because it goes down to 60.2 for 8 bit images. When I worked with jpegs I thought the fact that the Photoshop file size was larger was related to the compression of the closed file, but that's clearly not the case with CR2 files. Please help - I really want to understand this!

Answer 1

When sending pictures to libraries it is the flattened uncompressed size they want.
Documents can be altered to the required size using a script IE:-
var SizeOfFile = prompt("Please Enter Size In Megabytes",48)
if (SizeOfFile > 0) resizeToMB( SizeOfFile );
function resizeToMB( size_in_MB ) {
  var current_units = preferences.rulerUnits;
  preferences.rulerUnits = Units.PIXELS;
  var width_pixels = activeDocument.width;
  var height_pixels = activeDocument.height;
  var channel_count = activeDocument.channels.length;
  var final_size = ( 1024 * 1024 * size_in_MB ) / channel_count;
  var image_bytes = width_pixels * height_pixels;
  var image_scale = Math.sqrt( final_size/ image_bytes );
  var final_width = width_pixels * image_scale;
  var final_height = height_pixels * image_scale;
  var final_dpi = activeDocument.resolution;
  if ( image_scale > 1 ) {
    activeDocument.resizeImage( final_width, final_height, final_dpi, ResampleMethod.BICUBICSMOOTHER );
} else {
    activeDocument.resizeImage( final_width, final_height, final_dpi, ResampleMethod.BICUBICSHARPER );
  preferences.rulerUnits = current_units;