All your questions can be answered by three simple words. Because they
can.
On 12/9/2012 6:07 AM, Larry Colen wrote:
On Dec 8, 2012, at 2:39 PM, Tom C wrote:
From: Alexandru-Cristian Sarbu <alexandru.sa...@gmail.com>
Now everywhere I can hear them talking about stuff like growth or
doubling the sales in 2013. I'm hearing they hired back R&D engineers,
to make up for those fired by Hoya. They have 2-years roadmaps
totaling 8 K-mount lenses + 1 TC, 4 645D ones and 3 for Q; and, most
important, they're on track with the execution.
Alex, respectfully, I don't have that kind of insider information on
Pentax, so where do you obtain it? If their road map doesn't contain a
24 MP APS-C body, a FF body and lenses, then they're missing the boat.
I'm sure the market for either of those two cameras would dwarf the
market for a 645D or a Q.
Tom,
You've mentioned 24 MP a few times. How large are you printing that you need
24MP?
Also, what APS-C camera has that resolution? 4000x6000 pixels, on a 16x24mm
sensor, that gives 4um on a side for a pixel.
Using the diffraction calculator at:
http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm
f/2.8 has an Airy Diameter of 3.7 um or about 1 pixel
f/5.6 has an Airy Diameter of 7.5 um or about 2 pixel
f/8 has an Airy Diameter of 10.7 um or about 2.5 pixel
The page says:
As a result of the sensor's anti-aliasing filter (and the Rayleigh criterion
above), an airy disk can have a diameter of about 2-3 pixels before diffraction
limits resolution (assuming an otherwise perfect lens). However, diffraction
will likely have a visual impact prior to reaching this diameter.
In other words, with an AA filter, a 24MP APS-C lens will definitely be
diffraction limited by f/8.0. Without an AA filter, assuming that the lens is
sharp enough, diffraction is probably having an effect by f/4 or f/5.6.
4um is 250/mm, which I understand works out to 125 lp/mm.
Looking at DxOmark
http://www.dxomark.com/index.php/Lenses/Camera-Lens-Database/Nikon/Nikon-AF-S-Nikkor-35mm-f14G/(camera)/485
Nikkor 35/1.4 52 lp/mm
http://www.dxomark.com/index.php/Lenses/Camera-Lens-Database/Nikon/Nikon-AF-S-Nikkor-50mm-F18G/(camera)/485
Nikkor 50/1.8 53lp/mm
http://www.dxomark.com/index.php/Lenses/Camera-Lens-Database/Nikon/Nikon-AF-S-DX-Micro-NIKKOR-40mm-F28G/(camera)/680
Nikkor 40/2.8 is 49lp/mm
http://www.dxomark.com/index.php/en.../Lenses/Camera-Lens-Database/Pentax/smc-D-FA-MACRO-100mm-F2.8-WR/(camera)/676
Pentax DFA macro 100/2.8 is 46 lp/mm
http://www.dxomark.com/index.php/en.../Lenses/Camera-Lens-Database/Pentax/Pentax-smc-DA-35mm-F28-Macro-Limited/(camera)/676
Pentax DA 35/2.8 macro is 46 lp/mm
It seems as if you want a sensor that has approximately twice the resolution of
a very good prime lens, which correlates roughly with the Nyquist rate, which
would mean that you would never need an anti-aliasing filter, because even
without getting into diffraction limiting, you're already past the Nyquist rate.
Is this why you feel that 24 MP is so necessary in an APS sensor camera?
Bay photo seems to use 250 dpi as a print resolution:
http://www.bayphoto.com/bayweb/pro_fileprep.htm
Which, interestingly works out to 16x24 inches. However using the scaling of
the graph they use for Minimum Pixel size to yield good prints, they seem to
work with about five printer dots per pixel, which means that with a 4000x6000
sensor, you should be able to print at 80x100 inches. How often do you make
prints that large?
On the other hand, lower resolution would give more surface area per pixel,
which would increase both dynamic range, and signal to noise ratio. In my
photography, I find myself running up against these two far more often than I
run out of resolution in printing. By Bay Photo's chart, my K-5's 14 MP is
good for something like a 60x80 inch print. A 5x7 for people who measure their
prints in feet, rather than inches. I might be missing something here, because
I've never printed much larger than 18x24.
Although you implied market forces require that sort of resolution, which means
that the average photographer who uses their SLR as an expensive point and
shoot is printing that large. Or, are you just saying that it is one of those
marketing things, where people aren't satisfied with less than 300 cubic inches
of displacement in their car's engine, whether or not the customer would ever
use the power, or whether or not a car with a much smaller engine would
outperform it?
As I see it, I'm either not technically inclined enough, and I am totally
missing the analysis of why16MP, or even 12, is not enough, and why a camera
needs 24 MP in order to be marketable. Or, it could be that I'm far too much
of a geek, and am missing something critical by only looking at the physics of
the situation. The latter is quite possible, because I also can't understand
why suburban housewives in Coastal California where it never snows, need a
5,000 pound four wheel drive SUV, that seats eight, has a 6 liter motor that
puts out 300 hp.
--
Larry Colen l...@red4est.com sent from i4est
--
Don't lose heart, they might want to cut it out, and they'll want to avoid a
lengthly search.
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