Whoa! Check your assumptions. The Mpix numbers advertised for DCs are
approximately the number of 3 color pixels delivered in the output
(after all that complicated stuff you did). My 2.1 Mp camera produces
1600x1200 pixel images with 19,200,000 individual 3 channel pixels, so
it's really a 1.92Mp camera. I think most of them quote the raw specs of
the sensor, rather than the output of the actual camera design. It's
sort of like the way disk drive manufacturers advertise capacities in
decimal so that a 60mb drive is 60/1.024 or 58.59 mb to a digital
system. In both cases, the biggest number that is even sort of
defensible is used for promotion.
So, using your approach, but adjusted for the way Megapixels are quoted
for DCs and adjusting for promotional inflation, you need about 9 Mp to
equal 35mm film (even less for 25mm film!) I'm not necessarily agreeing
with the 9 MP number here, just disagreeing with your assumptions and 26
Mp conclusion.
Where it comes to where the rubber meets the road for me, all these
calculations don't mean much, it's the images and how people
react/interact, "see" them. It's clear to me that digital camera output
has certain qualities that differ subjectively from film and scanned
film. In the particular case of my eyes and those of friends and family,
DC prints are superior to 2720 dpi scanned 35mm prints for certain
common subjects at 8x10 and smaller. Assuming that's about the limit for
1.9 Mp, one would need about an advertised 8.4 Mp for 16x20, which is
about the limit for sharp 35mm prints using lenses of the quality you
assume and reasonable technique.
So your marhematical and my subjective approach end up pretty close. On
the other hand, C.H.'s examples make it empicically clear that 4000 dpi
(157dpmm) scans reveal more detail from at least fine grain film than
2700 dpi (107dpmm), so your 100 pixel calculated value may be suspect?
It leads one to suspect that something closer to the 18 Mp otheres have
come up with may be required to reach the resolution of fine grained
35mm film.
Moose
So here's another question. A significant number of this group view the
vast majority of their images as 4x6 automated prints. Why would they
need anything more than a couple of Mps, 0.5 for the 4x6s and the rest
for the occasional 8x10 with a little cropping? Of course, I except John
L., AG, you slide buffs and big print makers.
Remember what Mike V., who makes prints to sell said about 4 Mp:
"Largest I have gone so far from an E-10 file was 11x14. Print quality was on
par with an 11x14 custom enlargement from Provia F 100 film. In fact, I
picked up both from the lab at the same time and both the lab's store manager
and lab's owner were stunned by the results and we all agreed they
were quite comparable."
Moose wearing a Walt mask
Joe Gwinn wrote:
Comments interspersed below.
From: Albert <olympus@xxxxxxxxxxx>
with the introduction of the Kodak 14Mpx SLR, it would seem like you
can get what you never thought possible before, Medium format quality in
a 35mm SLR.
That depends on whose numbers you believe. My research indicates that an
optimal 35mm frame may contain as much as 18Mpx. Medium format may contain
40Mpx.
Reasonable 25mm film cameras resolve something like 50 line pairs per
millimeter; sometimes better in the center, sometimes less at the edges. At
two pixels per line pair, that's 100 pixels per millimeter. A 35mm frame is 24
by 36 mm, so we have (24*100)(36*100)= 8.64 million pixels (each having all
three colors), or (8.64)(3)= 25.92= 26 million pixels (as usually quoted for
digital cameras).
So, 18 Mpix is a bit low to be "optimal", but it isn't that far off: 26/18=
1.44 to 1.
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