At 08:53 3/25/02, you wrote:
I have routinly had slide exposures enlarged to 16x20. Many shots have
been enlarged
even greater.
Jim Couch
My personal limit is 11x16 inches, about 12X magnification of the
transparency. These are prints for juried exhibition in which *everything*
is very closely examined. This keeps its detail slightly finer than human
acuity can discern at *very* close viewing without additional magnification
and it's still well below grain structure. This limit is much tighter than
what can be used for large display prints for other purposes. 11x16 and
bigger requires a technically well-made (shake mitigation by some method)
transparency, or negative for that matter, using a high resolving lens and
extremely fine grain film, that is well-printed on an enlarger also using a
high resolving optical system.
Assuming everything from lens to film to enlarger have been optimized, it's
been my experience that 16x20 and larger magnifications depend on how one
defines both "acceptable image sharpness" and average viewing distance. It
is certainly possible to go larger, and it does force farther viewing
distance to take in the entire image. Humans will generally accept ability
to see resolution limits on very close inspection of extremely large prints
provided it is "graceful" (not harsh). I routinely project slow-chrome
slides to a 50 inch screen without any problem (requires a high resolution
projector lens). This is about 35X enlargement and it's a combination of
viewing distance and graceful degradation at resolution limits that allows
it. On close inspection of the screen, it is definitely possible to see
the resolution limits of lens, film, etc. Aside from giving slide shows,
it's my method to determine if an 11x16 can be made that will still have
detail levels finer than human acuity.
-- John
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