Mega Pixel Myth

On May 22, 9:52 pm, "dennis@home"
wrote:
"Scott W" wrote in message

oups.com...





On May 22, 10:02 am, SAMF2000 wrote:
The more megapixels your camera has the better the picture is the
myth. The truth is most good cameras do not need more mega pixels
unless you decide to enlarge the image larger than 4x6 image. an 8X10
Image might need 5-6 megapixels , but who really enlarges more than
this except for magazines and posters. My 3.2 megapixel camera is
great for 4x6 images and don't see any reason to upgrade.

I shot for a number of years with a 3.2 MP camera and would agree that
it was great for 4 x 6 prints, they look very sharp and clean. But
those same image when sized to fill my monitor (1280 x 1024) don't
look as sharp as what I get when I resize an 8MP image to fill my
monitor. Sure my 3.2MP image are not the sharpest (I was using a
Nikon CoolPix 995) but I 20 years from now I would expect to be using
a monitor with a lot more resolution the 1280x1024, hey I might have a
lot more resolution next year or even later this year.

A monitor is only ~1 MP.
If the 3.2 MP don't look sharp then its not the fact that they are 3.2 MP
that is the cause.
It is either unsharp from the camera or the scaling to fit the monitor isn't
very good.
Are they sharp if you veiw them 1:1?
First off when resizing to fill the monitor I have to use scale to
match the height of the monitor
and so the images where being size from 2048 x 1536 to 1356x1024, or
close to 1.4 MP.
I then have to crop soom off the ends of this image. Sure I could
size to fit the width, but then I would not be filling the monitor.

As I said my 3.2 camera was not very sharp, viewed at 1:1 not sharp at
all. But most cameras
will produce a much sharper looking image if it is down sized some
followed by a bit of sharpening.
This is not much of an issue when prints are being made a 300ppi since
the pixels are so small,
but on a monitor with its much larger pixels if the image is not sharp
at the pixel level it is easy
to see. And with any digital camera that uses a Bayer pattern its
images will look sharper when down sampled.

Yes a really good 3.2mp camera when resized to 1280 x 1024 should look
sharp, but what about when I am running a resolution of 2560 x 1600?
First off to fill that monitor if you are starting with a 4:3 image
you are going to need a image sized to 2560 x 1920, that is 5 MP right
there, and here is where you can get it today.
http://accessories.us.dell.com/sna/productdetail.aspx?
c=us&l=en&s=dhs&cs=19&sku=222-7175

I might not have one today, but I bet in a year or two I will have one
with the same resolution or more.

And there is no 5MP from a Bayer camera that will look as sharp as a
good 10MP image that is down sized to 5MP.

The point is that as display technology moves forward and image that
once looked sharp on a small low res display will look no so good on a
large sharp display.

In the early 80s I was at Tektronix when we saw a demo of a color
display system that looked fantastically sharp, the resolution was
640x480. Today this seems funny and you might think that you would
not have thought it looked all that sharp, but keep in mind this was
several years before VGA cards were out, and they could only to
320x200 in 256 colors. The point again is that what seems sharp today
will not seem to in a few years from now.

Scott




Anyway back to the original 6x4 v 10x8 sizes.
(Sorry to the OP that I missread what was said BTW.)

A 4x6 printed on a dyesub printer @ 300 dpi also needs 300 ppi for maximum
sharpness and detail.
so it would be 1800x1200 pixels, about 2 MP.
The same print done on an inkjet would only need about 100 ppi so about 0.25
MP (maybe 200 ppi @ 1 MP on an expensive inkjet).

A 10x8 on a dyesub @ 300 dpi would be about 7 MP.
On an inkjet it would need about 1 MP at 100 ppi or about 3 MP at 200 ppi.

You may notice that dyesubs have a 1:1 correspondance between ppi and dpi.
This is because each dot on a dyesub printer can cover the full tonal range.
On an inkjet you have to be able to print ~750 dots to represent a pixel
(256x3). This means the ppi is about twelve-sixteen times less than the dpi
for the printer.

So you can see that for home printed pictures using an inkjet you only
really need 1-2 MP to do 10x8. Very few home users will be able to make use
of a 10 MP image without throwing most of it away.
However a large image does give more options for creating the final image.- Hide quoted text -

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