Where do I get a walk through on how to change the Adobe Photoshop's default magnification?
Walk through for Adobe Photoshop
Sadly there is no way by which you can change the default magnification of Adobe Photoshop. The only thing that you can do is open the image in Adobe Photoshop first and then zoom in/zoom out the image with the help of Zoom tool  presents on the sidebar as shown in the picture below:
As soon as you click on the zoom tool, a toolbar like this would appear below the upper menu bar as shown:
From here you can choose accordingly the zoom-in magnifier or zoom-out magnifier.
You can also use the following keyboard shortcuts instead too:
 |
WINDOWS |
MAC OS |
Zoom in |
Ctrl + (plus) |
Cmd + (plus) |
Zoom out |
Ctrl – (minus) |
Cmd -(minus) |
Actual pixels |
Ctrl Alt 0(zero) [you have to press all buttons together] |
Cmd Option 0(zero) |
Fit on Screen |
Ctrl 0(zero) [you have to press all buttons together] |
Cmd 0(zero) |
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