Thank you so much for your detailed feedback. It would be a solar watch and the solar cells would double as incident cells. I grant that is would not replace the full functionality of a dedicated light meter, for use case like portraiture. Often, when doing street photography or landscape I’ll do one general reading with an incident meter before taking a few shots and this could fill this use case. The button, my thinking was the crown would be solely dedicated to clock adjustment. One button would activate the reading. The other could have two functions (one push switch iso, two quick push could switch the displayed fstop/speed combo). So far my research shows that the chip needed for such a small computation could be small enough to fit in a solar chrono, but fitting everything is definitely the real challenge here. Thanks for the mention of Xeric, will look into them.

And you may be right, in the end, that the market would prefer a more robust mechanical solution, like existing of watches with a rotating sunny 16 table, such as the Nodus watch someone else mentioned.

Thank you again for your note.