When whe specs of a camera say that the viewfinder has e.g. 95% coverage, does it refer to the area or diagonal angle of view?
I'm more inclined to think it's about the area, but couldn't find confirmation and both seem plausible.
I found this article on luminous landscape saying that:
To further confound matters, coverage is sometimes reported as a linear measure and sometimes as an area measure. To simplify this, imagine a big square drawn on graph paper that has ten little squares per side. The linear measure is 10 x 10 little squares, and the area measure is 100 little squares. Now imagine that we're going to draw a slightly smaller square inside the big one that's smaller by one little square on each side. That square has eight little squares on each side. The linear coverage of the inside square is 80% of the larger one (8 instead of 10); the area coverage is 64% (8 x 8 instead of 10 x 10). You can see from this that when one camera manufacturer reports that its viewfinder has 92% coverage and another reports 95% coverage, you still can't quite be sure how they compare, because one might be reporting linear coverage and the other area coverage. (And an educated consumer is a....)
In short, the area coverage would be the square of the FOV coverage thus a FOV coverage of 95% would mean roughly an area coveage of 90%.
