Need help in calculating digital camera's MP

On Sat, 03 Jan 2009 19:09:10 GMT, "David J Taylor"
wrote in
:

John Navas wrote:
On Sat, 03 Jan 2009 18:26:14 GMT, "David J Taylor"
[]
John, I appreciate all of that. I specifically asked about studies
comparing RGB to Bayer, and the number of pixels or resultion to
make the two equivalent.

I obviously have no idea what you want, and can only suggest again
that you get thee to Google. You'll find there's no simple answer
(like your 2x).

This is beginning to sound a bit like the pointless Foveon wars. I
don't want to do that again, and I'm personally not terribly
interested in resolution the eye can't see, but whatever floats your
boat.

I agree that there's no simple answer, that's why I thought someone might
have done a study. It sounded like a good PhD topic!

So riddle me this, David: You're quite prepared to make a pretty
aggressive resolution assumption based just on speculation about
dissimilar devices (Foveon, 3 CCD), not "studies", but pay no attention
to hard data I provide on human perception, demanding precise "studies"
instead. Why is that?

--
Best regards,
John
Panasonic DMC-FZ8, DMC-FZ20, and several others

John Navas wrote:
[]
So riddle me this, David: You're quite prepared to make a pretty
aggressive resolution assumption based just on speculation about
dissimilar devices (Foveon, 3 CCD), not "studies", but pay no
attention to hard data I provide on human perception, demanding
precise "studies" instead. Why is that?

I didn't ignore the data on human perception, John, but that is well-known
to me. Human perception is only half the story. It's what happens when
you combine perception with the image production method which matters, and
I feel that will be a subjective result rather than something you can
calculate, and hence the possible need for further study.

I was looking for guidance on what the figure might be, and suggested one
possible value - 2 in area, 1.4 linear. I did wonder if anything useful
had come from comparisons between Bayer and either Foveon cameras or 3-CCD
cameras.

David

TheRealSteve wrote:
[]
Of course it's not as good as a high-quality JPEG. But you won't
notice any difference viewing it on most TVs. And of course it's less
flexible. But we don't need flexability ... we're authoring a DVD.
The advantage it gives you is the ability to use the entire screen of
a widescreen TV, without any noticable disadvantages.

Steve

The OP mentioned nothing about wanting to use a DVD, IIRC.

David

Paul Furman wrote:
[]
Whether 720 or 705... you are saying that's the most a TV can do
without burning blu-ray format (is that even possible?). If so I'd
say this makes TVs pretty much worthless for viewing still photos.
Even a projector will do 1024x768.

To get full resolution, you need to avoid using a CD/DVD as the input
medium, and either use the VGA connection on the back of the TV, or
perhaps (depending on the TV), the SD-slot.

Cheers,
David

wrote:
Thanks for the replies and discussion (which most of them I don't
quite understand).
[]
However, I still did not have any responses (except perhaps one) on
what happens for those TVs like Sony and Panasonic, which you can just
plug in a memory stick (Sony) or an SD card (Panasonic) in the slot
directly. Do such TVs have special processing inside so that the
photos will come out good? They must have done so, otherwise they
cannot "sell" such feature in the TV. I was initially thinking about
getting the Panasonic TV which has the SD slot, but it does not come
for the LCD (only in plasma).
[]

The TV will already include an interpolator either in hardware or firmware
to ensure that the full resolution of the screen is used, whatever the
source (i.e. that 640 x 480 isn't displayed as a postage stamp in the
middle of the screen). I don't know whether there is any standard for
that interpolator when reading images from SD cards - take a sample into
the store and check. I believe that some TVs will display at full
resolution.

Given that there is an interpolator present, there's no fundamental reason
why full resolution images from a CD or DVD shouldn't be displayed at full
resolution on the screen, but it may be that some "standard" for having
images delivered from that source /must/ be taken at a lower resolution.
Again, a trip to the store to check before purchase should resolve that.

Cheers,
David

David J Taylor added these comments in the current discussion du
jour ...

HEMI - Powered wrote:
[]
David, we've had this discussion ad nauseum, namely is "more
mega pixels better images" or not. You are obviously correct
that few cameras other than toys are less than about 6 MP but
that hardly means they are all created equal.

Indeed - how annoying might the small amounts of pincushion or
barrel distortion in many of today's zoom lenses be when viewed
against the dead straight edges on a LCD or Plasma display, if
left uncorrected. I suspect that a 1920 x 1080 HD TV display
worthy of the name would provide quite a critical environment
for viewing images, if for no other reason than its physical
size. You should certainly see the benefits of a higher-quality
source image.

David, I have to say "Huh?!" again here. Yeah, I've seen barrel
distortion in a FEW of my pictures depending on lens and focal
length but I always fix it BEFORE final save, so if I were
displaying on my TV or a HD wide-screen as is the OP, then it would
not longer be an issue.

--
Jerry, aka HP

"If you are out of work and hungry, eat an environmentalist" -
Florida billboard

David J Taylor added these comments in the current discussion du
jour ...

HEMI - Powered wrote:
[]
Huh?! How does the way a camera "sees" a pixel translate into
how a TV sees one? Or, a PC monitor? 16 million color requires
3 bytes per pixel, of course, but how does this matter to a TV?
Isn't it far more important how the TV system that reads
digital images from, say, it's memory card slot, depend on how
well it fills the screen from whatever it is provided?

Inded, yes. What I was saying was that in the camera, what we
call 2Mpix is not 2Mpix of red, 2Mpix of green, and 2Mpix of
blue, so the overall image resolution in RGB pixels is somewhat
less than 2Mpix, perhaps 1Mpix for the sake of argument.

However, the display does have as many RGB pixels as specified
(i.e. 1920 x 1080), and so it can actually display 2Mpix of RGB.
So if you want the display to be the limiting factor, send it
rather more than 2Mpix of RGB, i.e. something like 4Mpix derived
from a Bayer-sensor camera.

I can't see how it matters how a camera "sees" a pixel internally.
By the time I get to see it on my PC, it IS a normal 3-byte tuple,
so a given number of MP is accurate.

True enough but my Canon DSLR creates 3:2 images. But, whether
a camera is 4:3 or 3:2 or something else, to get all the way to
a 16:9/16:10 aspect ratio also requires the photographer to be
VERY aware of how they must crop their images or something
important will likely be lost.

Yes, and having a 16:9 crop frame visible in the finder would be
a help. You see this in reverse in TV work, where although the
cameras are 16:9, they have the older 4:3 aspect ratio marked
(perhaps even with a slight margin), so that the "important"
action isn't lost on viewers with older sets....

I agree, but then, it would also be nice on a 3:2 camera if a 4:3
crop frame were also visible, same reason.

It is interesting to me, and very disconcerting, that the PC
monitor makers seem all of a sudden to have abandoned 4:3 monitors
past about 17-19", with seemingly no regard that at this time, FEW
people have images of a 16:10 ratio to display without some major
cropping and re-editing.

--
Jerry, aka HP

"If you are out of work and hungry, eat an environmentalist" -
Florida billboard

HEMI - Powered wrote:
[]
David, I have to say "Huh?!" again here. Yeah, I've seen barrel
distortion in a FEW of my pictures depending on lens and focal
length but I always fix it BEFORE final save, so if I were
displaying on my TV or a HD wide-screen as is the OP, then it would
not longer be an issue.

Yes, of course, anyone who cares about their image quality would indeed to
that. BTW: if I recognise it's going to be an issue in an image, I would
make fixing it the /first/ step of the processing. The point, though, was
that displayed on a large screen, these defects may be more noticeable.

Cheers,
David

David J Taylor added these comments in the current discussion du
jour ...

HEMI - Powered wrote:
[]
David, I have to say "Huh?!" again here. Yeah, I've seen barrel
distortion in a FEW of my pictures depending on lens and focal
length but I always fix it BEFORE final save, so if I were
displaying on my TV or a HD wide-screen as is the OP, then it
would not longer be an issue.

Yes, of course, anyone who cares about their image quality would
indeed to that. BTW: if I recognise it's going to be an issue
in an image, I would make fixing it the /first/ step of the
processing. The point, though, was that displayed on a large
screen, these defects may be more noticeable.

I agree with you that fixing either barrel or pincushion distortion
should be the first thing done because it allows the FULL mega
pixels of the image to be corrected. As I said, I only rarely see
any of this at all, but when I do, it is usually on something
decidedly rectangular, like a sign or placard I shot to describe
the main subject for information purposes.

I would also comment that other than correction lens distortion,
the next thing I do is to correct any apparent perspective
distortion and then crop horizontally for best preliminary
composition, resize horizontally to the final size, then crop
vertically for best composition. To allow all of those things to
work reasonably well, IF I can, I leave maybe 20-25% of "white
space around the main subject. Sometimes I cannot do that, for
example, when shooting a car at an outside show or in a museum
where the widest lens I want to use isn't wide enough and I can't
go back further without either running into another car OR in
ruining the basic composition by bringing in too much of what is on
either side of it.

These are all valid points. I only have one HD-capable TV right
now, a 27" Sony that also can function as a PC monitor but only at
1024 x 768. I have ran a number of images to this TV via a
Panasonic DVR that has an SD card in it. I don't think the Sony's
resolution is quite as high as 1920 x 1080, I think it is more like
1780 or thereabouts, but on the occasions I've tried looking at
JPEGs, I saw no quality issues due mainly due to the camera.

But, to the OP's main question, I imagine they could answer it
fully on their own by simply testing some typical digital
photographs that are all basically identical except for the mega
pixel size and simply observe whether a larger image does or does
not truly improve what the eye can see.

Have a nice Sunday, David!

--
Jerry, aka HP

"If you are out of work and hungry, eat an environmentalist" -
Florida billboard

HEMI - Powered wrote:
[]
I can't see how it matters how a camera "sees" a pixel internally.
By the time I get to see it on my PC, it IS a normal 3-byte tuple,
so a given number of MP is accurate.

Yes, at the computer it's a 3-byte RGB triple, but the camera hasn't
sensed it that way. At the camera, each pixel will only record one
colour, in the so-called Bayer pattern, so that if you consider two rows
or two columns of sensors, at the camera it's typically:

(R--) (-G-)
(-G-) (--B)

and the camera's firmware converts these four value to 12 values when
presented to the PC:

(RGB) (RGB)
(RGB) (RGB)

The conversion works very well, but it's not perfect, so some resolution
is lost during the process. The question I am asking is: how many Bayer
pixels are required to provide full quality on an RGB display?

[]
I agree, but then, it would also be nice on a 3:2 camera if a 4:3
crop frame were also visible, same reason.

It is interesting to me, and very disconcerting, that the PC
monitor makers seem all of a sudden to have abandoned 4:3 monitors
past about 17-19", with seemingly no regard that at this time, FEW
people have images of a 16:10 ratio to display without some major
cropping and re-editing.

Yes, quite it's why I got my 1600 x 1200 monitor - 4:3 aspect ratio -
while I still could. Now my images are more likely to be 3:2 aspect ratio
from a DSLR, and I expect my next monitor will be 16:10 (1920 x 1200), and
I will just accept the black bands....

Cheers,
David