Zoom factor quantification

Hi, I was curious to ask, is there a specific module or window in 3D slicer that displays the zoom factor changed by the mouse as a percentage, or allows it to be set to a specific percentage? (for example, I have 3 scans of 3 different individuals I will be manually segmenting the same structure out of, and I want to be able to set all at 200% as the zoom level to avoid error in my visual recognition of the dimensions of the structures between individuals). Using Slicer 4.11. Thank you for your help!

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Hello, Cetus. Good question.

I don’t know an answer to your specific question in terms of percentages, but perhaps for your purposes you could use the Field of view setting that I found in the View Controllers module? If you link all of the views (with the linked rings button), then you might be able to quickly set all views to the same magnification?

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I’m not entirely certain of precisely what the Field of view setting means, because I noticed that if I drag to increase the size of the module pane (on the LHS of the GUI), thereby shrinking the viewport sizes, the Field of view setting is unchanged; in so doing the magnification doesn’t change, but less of the slice can be seen horizontally on screen. On the other hand, if I switch from a Four-Up Table layout to a Four-Up layout, thereby expanding the viewport sizes, the Field of view setting increased (from 22.00 to ~36.1); in so doing the magnification doesn’t change, but more of the slice can be seen vertically on screen.
So, based on that, I suppose it is linked to how much a slice can be seen (on screen) in the relevant viewport, measured vertically (in the on-screen direction).
Then I guess it should be comparable across different scans if you retain the same layout for each scan.

When it comes to a percentage magnification, I suppose that strictly speaking the size of the computer monitor would also be relevant.

—DIV