In article , AG Schnozz <agschnozz@xxxxxxxxx> writes
81x36mm=2916 lp horizontal (round to 2900)
81x24mm=1944 lp vertical (round to 1900)
With the Canon D1S, the CCD is 4064x2704 pixels. This gives a
maximum lp/mm of around 57 lp/mm or aound 2000 lp horizontal.
However, that assumes perfect alignment of the pattern and the
array. A more accurate resolution is more like 38 lp/mm which
is about 1350 lp horizontal.
Velvia has almost 2900 lp across the width of the image.
Canon has almost 1350 lp across the width of the image.
Sadly, this type of gross analysis inevitably ignores the question of
what actually is important to the end user - the limiting resolution of
the system or the practical resolution achieved. Resolution is useless
to the photographer unless it is achieved with a practical and useful
contrast. The limiting resolution is a synthetic limit based on one
individual or organisation's definition on what that practical limit is.
Examination of the MTF chart for Velvia at
http://www.fujifilm.com/JSP/fuji/epartners/bin/AF3-960E.pdf
shows that not only does it not reach 81cy/mm at all, but at most
achieves 60cy/mm and even then the MTF of the film is only 30-35%.
At the Nyquist sampling resolution of a CCD however, the MTF is at least
64% and, depending on the fill factor, can be significantly higher. At
that minimum level of sensor MTF however Velvia reproduces at most
30cy/mm.
Your unilateral reduction of the resolution of the digital sensor based
on the need to align with a synthetic bar pattern target is totally in
error - resolution does not require alignment with anything and there
are many ways to measure resolution and MTF which are far more accurate
than the test chart you allude to.
Based on the MTF of the CanonD1S at its limiting resolution - which *IS*
the nyquist of the array - Velvia is a much poorer performer in terms of
how sharp the image appears to the end user. Hence the reports from
users of CanonD1s and lesser digital sensors that the results far
outperform 35mm film. In terms of their limiting resolution, your
analysis shows that they do not, However the paradox between that
grossly simplified calculation and practical experience merely
highlights the fact that limiting resolution is rarely, if ever, the
most important parameter.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers
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