Yes, I was aware of the use of overlays in photo's for astronomy.
But Mr. Scarpitti is the person who mentioned 'side by side'
comparison. And wasn't speaking of the blinkscope method of
comparison it would seem.

Dennis

"normanstrong" wrote in message
...
"Dennis Moore" wrote in message
...
"Michael Scarpitti" wrote in message
news:2Xifb.
No, it does not apply to photographic lens testing. The results
are
fixed on film and visible at any time. Side-by-side comparisons
are
possible.


How would lens testing be different? Yes, side by side comparisons
are possible. But you can only look at one photo at a time.
Switching between them still means a delay and memory is
involved all the same.

Dennis

Have you ever heard of the "blink microscope"? Zeiss designed this
device almost 100 years ago. Its purpose was to discover whether any
of 1000's of stars had moved between 2 photographic exposures of the
same piece of sky. Memory is not involved; you are looking for
movement only.

Norm Strong