Have you ever been zoomed in while editing in Photoshop, only to zoom out and realize your adjustments were not at all what you wanted? Here is a quick solution I like to use to avoid that situation.
1. Opening a New Window
With your image open in Photoshop, from the menu bar, navigate to Window > Arrange > New Window for (filename). A second tab will appear containing a duplicate version of the image.
2. Arranging the Windows
From the menu bar, navigate to Window > Arrange > 2-up Vertical (or whichever orientation works for the image).
There will now be two windows of the same image side-by-side.
3. Decide on Zoom
If you wish to have both images zoom together, checking the box for Zoom all Windows will accomplish that. On occasion, I have set one window at 50% zoom and left the other at fit screen. When zooming in, I am then able to work at 100% while also viewing a zoomed version along with a larger area of my image simultaneously. However, I typically like to see the full image in one window while zooming with the other. Uncheck this box if you do not wish to automatically zoom both windows. You will still be able to do so manually on each window.
The images will now be viewable at two different sizes. I love using this technique when cloning or editing skin. Try it out and see what you think!