Joe Gwinn wrote:
Comments interspersed below.
Likewise
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.
Huh? Check decimal point. Ah: 1600x1200= 1,920,000 pixels, but each pixel is
of just one color, red, green, or blue, so we don't have the equal of a camera
with 1.93 million tri-color pixels. The ratio of colors is 1:2:1 for R:G:B, so
there are 1.92/2= 960000 green pixels, 1.92/4= 480000 blue pixels, and 480000
red pixels. The resolution is set by the green pixels; the other colors are
interpolated to fill in the missing values. So, a 2.1 Mpix camera actually has
0.96 Mpix of true tri-color resolution.
OK, so fool that I am, I assume when people argue/discuss the number of
Megapixels needed to match 35mm information content that they are
talking about the 3 color pixels in the output produced from processing
the raw signal from the imaging device, not the number of individual,
filtered, image sensing points on the CCD/CMOS/?? sensing device. When I
see camera specs, the number of 3 color output pixels is roughly equal
to the advertised Mp of the device. So you are talking about sensor
design detail and I'm talking about device output, however produced by
interpolation, mixing, mashing or mulching, no? I don't particularly
care about what's underneath, as I'm empirically estimating the number
of advertising spec. Mps needed to produce what I consider a great print
of a large size from the number needed for a smaller print. I realize
what's underneath counts, but I read the reviews and will only consider
a camera with good review results.
Interestingly, the same simplistic area math says a 3.7Mp output for
11x14 is equivalent to 1.9 Mp for 8x10 and that's the size Mike M. says
gives such good results from the 3.7 Mp (effective) E-10. Steven S.
touts even larger excellent results, but with the aid of special
upscaling software.
So which number are the folks who come up with the 18Mp as the point
where digital may match 35mm using?
Actually, one needs always to look for the "optical resolution", as the
1600x1200 may have been interpolated from a lesser number of actual CCD pixels (of any
color). The true resolution cannot exceed the optical resolution, regardless of the
nominal resolution of the format. Interpolation cannot supply the missing picture detail.
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.
Not so. My claim is that one needs more like 25 Mpix (sum of red, green, and
blue pixels in 1:1:1 ratio), which is the equivalent of 8.64, call it 9 million
tri-color pixels.
I thought that's what I said too, it's just that we're talking different
ways about the numbers. So what is the 14Mp Kodak? I'm guessing that by
your calculations, and assuming 1:1:1 sensor design, that you would call
it a 42Mp sensor?
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.
While beauty is in the eye of the beholder, I would comment that there is a lot
of equipment in the chain from scene to photograph in each case, and if any
element in the chain isn't up to standard, the photos won't be good. So, I
would be cautious about making sweeping generalizations from two photos or two
specific sets of equipment.
I generally agree, although less for the DC than for the Olys. Most of
the S110 images are ready for printing, except sometimes for cropping,
right out of the camera. Reviews showed that the diminutive S110 had
some compromises in performance compared to it's physically larger
siblings, so I don't think I am using some unusually great 2 Mp DC.
Moose
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