Methinks I discovered the reason for the percieved problem.
In the old applications, as in other programs (Android, Win et al.), the action
of zooming in/out is performed in a similar way, e.g. 'standard by convention' -
The focus is zoomed in/out from a center spot on the screen.
When the zoom occurs, the eye is fixed in the center of the screen, and does not
move it's focus, the eyebal is stationary (no muscle action on the eyeball or
refocus of eye's lens). Thus no muscular activity.
The Apple marketing/scientists decided it would be cute to zoom in/out from the
position selected (tapped) on the screen, so that the application zooms in or
out from a visually non expected location. Often this is from the sides
(upper/lower corners).
This ever slow and slight motion from a new spot on the screen causes the eye to
quickly search or twitch while relocating focus, as this is really an
unexpected movement.
Think of it like a DSLR camera's auto focus mechanism.
Even though focus on the same visual depth plane, there is a side to side shift
that the camera (eye) needs to accomodate, and a lag. This is heard by the
slight lag and focus motor grinding. In the eye the trauma occurs from
repetitive side shift and refocus
This was compounded by the fact the zoom is slow, so the eye tries to adjust
quickly.
Maybe the quick and programming easy fix would be to accelerate that zoom, so
that the eye does not have a chance to physically move.
This feature is implemmented in high end cameras. When in continuous auto focus
mode, you set a delay in the focus/refocus mechanism. This is useful in sport
events, when someone crosses in front of the field of view, the focus stays on
the selected spot.
Can the iPhone be considered a sporting tool?
Can I get a Nobel prize??