Document Size and Image Size

[jshhndsd]

Hi Guys,

Recently I just realised that if I open an image in PS and resize it using Image > Image Size, it resizes the entire document/canvas plus the image itself. However, if I create a new document and place/copy and paste an image within this new document as a new layer and attempt to resize it, it does nothing. Yet, I can resize using the transform tool. Another observation was that the first method reduced the resolution whereas the second method doesn't. I am interested to know why this occurs and is it possible to resize the image on a new layer within an existing document using Image > Image Size?

Thanks in advance.

 

[revnart]

I have hard time understand but hope this helps:
Image > Image Size - takes whole image (document) with all layers as one. You can't resize one layer, for example placed from anther document and resize it using this command - it appears as nothing is changing because proportions of layer to documents stays the same only overall dimensions change.
Another thing is resampling checkmark in this window (Image > Image Size). Because you may be changing just the size of this document when printed but changing its PPI, which just changes density of pixels which decreases or increase size when printed bot not visible change will occur on monitor because number of pixels is not changing.