Hi again Mike ;-)

No, I'm going the reverse way. I am saying that 6 MP is interpolated to
make a decent 8x10" print, and that the underlying data is circa 40 lpmm
resolution equiv. on a 35mm film SLR. Partly, this is due to the
anti-aliasing filter in DSLRs/EVFs, partly other system losses etc.

As for prints, I am NOT claiming that 24 MP means a 16x20" prints at 6MP
8x10" print quality. I am saying that 24 MP (Kodak's estimate for
mid-speed films, "at least") is equal to about 84 lpmm on film. That is a
high but not impossible resolution for slow speed 25-100 ISO films and
very good lenses and technique.

To get a Leica standard 8x10" print, held at 10", you need 8 lpmm on the
paper. Using 24x36mm film, you need an 8 times enlargement factor to do
an 8x10" print. So 8 lpmm * 8X = 64 lpmm needed on film. Add in losses in
enlarging lens or scanning lens and you need well over 64 lpmm on film to
make a leica standard print. So our 24MP equiv. is easily able, at 84
lpmm, to produce an 8x10" Leica standard print. But it can't do so at
16x20", as you infer, as the math here shows. So that's why I'm NOT saying
that ;-)

The implications of the popphoto rating of 100 ISO film at 40 megapixels
is that you can put about 108 lpmm onto film, with the best lenses and
technique. Again, this is in good agreement with a lot of test reports
etc. This would permit an enlargement factor of 13X, meaning a 13"x 19"
print to the leica standard of 8 lpmm on paper (no losses in lens etc.).

Again, neither of these claims is remarkable to most darkroom types or
those reading lens test reports and film resolution values of mfgers etc.
When you make the equiv. calculations for how many Megapixels this
represents, you find that most of the information on film is being lost in
conversions and scanning to digital files. That info is the 60% or so
above 42 lpmm (to 107 lpmm per popphoto tests).

That's why we film "luddites" are screaming foul! ;-) The scanning process
is losing 60% of the data. Yes, the images may still look okay from a 6 MP
camera. But you _don't_ have the fine resolution data. David L. seems to
believe this data is not important to the image - his subjective opinion
and valid for him.

For many of us, we have seen the difference between 40 lpmm lenses and 70
lpmm and even 100 lpmm lenses, and this is why we go for the higher
contrast and higher resolution lenses, even at considerably higher expense
over the trash cheapy lenses which can only deliver 40 lpmm (i.e., digital
camera quality, again, which is limited by the low pass filter for
anti-aliasing in the camera).

So I am saying that 6MP makes a nice image because it is interpolated to
fill in and smooth out the missing data, but close examination should show
that the image lacks the really fine detail and high contrast that
typifies high end lenses and film with proper technique (i.e., beyond 40
lpmm and into 70-100+ lpmm ranges). This is why it takes 24 MP for film to
produce a Leica standard 8x10" print with this kind of high resolution and
fine contrast detail. The 6 MP can't do so, because it lacks this high
frequency data, again, due to the anti-aliasing filter. The digital image
is effectively one taken thru a softening filter of moderate strength.

And so that is the digital vs. film quality difference. The digital image
is essentially what you would get if you shot film with a softening filter
in place - i.e., the anti-aliasing, low pass, softening filter used in
most DSLRs to prevent aliasing. When you take off the softening filter
with a film camera, you get noticeably better contrast and fine detail.
That is the essential difference between digital and analog imagery today.

my $.02

;-) bobm
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* Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 *
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