Use an Openmv camera as viewfinder for analog cameras. Which focal length could be used?

I would like explore the possibility to use and Openmv cameras as electronic viewfinder to be applyed on a analog camera. The sketch LCD_1.py from the examples could be a good starting point ( I don’t expect an huge resolution ) , but I’ve not idea at all of which focal leng I could use on the sensor to cover the same view of an eye close to the camera viewfinder.
Any suggestion ?

I’d just buy all the lenses we supply and pick the one that works best for you.

Note that we actually have to try a lot of lenses online to downselect what ones work. I do not recommend just buying random ones online. However, if you want to be exact, I recommend buying lenses from commonlands.com - they tell you the exact specs per camera sensor for each lens they offer and the FoV, etc.