# Zoom factor quantification

**URL:** <https://discourse.slicer.org/t/zoom-factor-quantification/20603>\
**Category:** Support\
**Created:** [November 12, 2021, 5:17pm UTC](https://discourse.slicer.org/t/zoom-factor-quantification/20603 "2021-11-12T17:17:06Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![CETUS](https://avatars.discourse-cdn.com/v4/letter/c/c2a13f/32.png) [@CETUS](https://discourse.slicer.org/u/CETUS)\
**Post date:** [November 12, 2021, 5:17pm UTC](https://discourse.slicer.org/t/zoom-factor-quantification/20603/1 "2021-11-12T17:17:06Z")

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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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**Author:** ![DIV](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/div/32/12816_2.png) [@DIV](https://discourse.slicer.org/u/DIV)\
**Post date:** [November 15, 2021, 7:13am UTC](https://discourse.slicer.org/t/zoom-factor-quantification/20603/2 "2021-11-15T07:13:28Z")

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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**](https://slicer.readthedocs.io/en/latest/user_guide/modules/viewcontrollers.html#panels-and-their-use) 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?

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/b/1/b1f5a1eeaefe2d6da7ad05e060d8f8374c19990a.png)

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