Since most folks view their pictures on 16:9 long horizontal monitors on their PCs, and seldom ever print them for hardcopy, it will be a long time since smartphone usage is long vertical but the images that are viewed are on PCs and TVs at home with long horizontal.Just reading the news I came across this tidbit.
https://mashable.com/article/youtube-vertical-video-ads/#I74CB_t9SaqL
With the smartphone becoming the viewing device of choice, YouTube is now approving vertical video ads, and is apparently late to the party. Will we see new cameras with vertical viewfinders in the future? Most of my photographs are horizontal, but two of my recent photographs accepted for publication were vertical. Are they harbingers of a trend?

