Capturing opens via Mobile Device?

[Jamie_Barclay]

I'm looking to identify the opens via (any) mobile device so I can define a ratio of opens via mobile vs. overall opens.

Can you tell me if by adding the "Is Mobile Device" will capture all opens via a mobile device or do I need to drill down further (i.e., Device/platform)? 

I ran across this article:

https://nation.marketo.com/message/125207#comment-125207

[Josh_Hill13]

It will help.

Opens aren't accurate and it will be even less accurate than this. Will be directional. See

Device and Client Counting Methods in Marketo - Marketing Rockstar Guides

If you use Email Insights,you may find this data faster. But if you want the actual leads, you can use the method you are trying.