Why pixel peeping (usually) makes no sense

On Sat, 17 Nov 2007 13:37:37 +1100, "cmyk" trolled the group
with the following words:

"ClarkJohnson" wrote in message ...
On Sat, 17 Nov 2007 10:54:04 +1100, "cmyk" wrote:

"ClarkJohnson" wrote in message ...

Your whole post betrays your lack of experience with reality and photography in
general. Print quality is more dependent on subject matter than it will ever do
with PPI settings.


And just where did I say that subject matter was unimportant, or less important?

But since *you're* claiming "Print quality is more dependent on subject matter than it will ever do with PPI settings", perhaps
you'd care to back that up with some evidence.

That's easy. Take a picture of a red square with a 1-pixel resolution camera.
You can blow it up to the size of a billboard and it'll still have the same
amount of detail, color, and retain the same shape. The same is true of any
subject depending on what kind of details are in it to begin with.

That would have to be the lamest 'evidence' possible. It's an insult to your intelligence.


No, the fact that you can't see why that's a prefect example is highly revealing
to your lack of intelligence and experience with varying subject matter.

If you take a screen dump of any worthwhile image and print it to a full sized A4/letter page, it'll likely look awful from a normal
viewing distance, even if printed at 1200dpi or more. Doesn't matter how good the image was. Likewise, if you take a 50Mp image then
downsample it to 100dpi for a 6x4 print, all you'll end up with is mush.

Again you reveal your lack of intelligence. If you use a Lanczos8 or Sinc256
resampling algorithm that image will not be mush. It'll be perfectly fine.
You've probably been reading too many PhotoShop users who only have bicubic as
their only option. They're not too intelligent either.

No sense wasting my time replying further, you obviously have very limited
experience with these things, and even less intellect to discuss them to the
depths that would be required.


The simple fact is that the print resolution is just as important as the subject matter.

If you've got a decent image, then printing it at the optimal print density for the size and viewing distance will give the best
results. Any interpolated image whose density isn't evenly divisible by the printer's maximum resolution is going to suffer. You see
it all the time on-screen when there's a mismatch between the the number of pixels in the image and the number available for
displaying them. Printers suffer from the same limitations, just not so noticeably. Throwing away a few pixels around the margins,
printing to a slightly smaller size to avoid such interpolations, or using a higher resolution that suits the printer (which might
amount to the same thing) is generally preferable.

"ClarkJohnson" wrote in message ...

If you take a screen dump of any worthwhile image and print it to
a full sized A4/letter page, it'll likely look awful from a normal
viewing distance, even if printed at 1200dpi or more. Doesn't
matter how good the image was. Likewise, if you take a 50Mp image then
downsample it to 100dpi for a 6x4 print, all you'll end up with is mush.

Again you reveal your lack of intelligence. If you use a Lanczos8 or Sinc256
resampling algorithm that image will not be mush. It'll be perfectly fine.

Glad to know you think a 6x4 print at 100dpi is perfectly fine. At least now everyone knows how low your standards are.

No sense wasting my time replying further

Agreed

--
cmyk

On Fri, 16 Nov 2007 23:15:56 GMT, Calvin Drayer
wrote in :

On Fri, 16 Nov 2007 08:49:35 -1000, Scott W wrote:

I also would take some issue with your table of needed pixels, this is a
personal thing. For an 8 x 10 print I would say 4MP is acceptable, but
just and very good would be 8MP. And with a good printer you can see a
noticeable improvement going from 8 to 16 MP for a 8 x 10 print, so I
don't see how even 8MP could be call best for this size print.

It's clear that you never do much photography, nor printing. Even more important
than the number of pixels is the subject matter. With the right subject matter
even the images from 1.2MP cameras (with good optics) can print exceptionally
well at 8x10 sizes.

Really? Example please.

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)

On Sat, 17 Nov 2007 09:49:47 +1100, "cmyk" wrote in
:

"John Navas" wrote in message ...
On Sat, 17 Nov 2007 09:10:43 +1100, "cmyk" wrote in
:

"John Navas" wrote in message ...
On Sat, 17 Nov 2007 08:13:14 +1100, "cmyk" wrote in
:

For my 7.2MP Panasonic FZ8, 11x14 is "excellent" at about 216 DPI.

To produce an 11x14 print without interpolation from your FZ8, you can only print at 200ppi. Printing at 216dpi is only going to
degrade the image through interpolation. You can see what's optimum by dividing the print dimensions by the available number of
pixels. That gives an angular resolution of around 115 arc-seconds.

With all due respect, that's an essentially meaningless distinction.

You would do well to take time to study this instead of peremptorily dismissing it.

Been there; done that.

Your response betrays a certain lack of
understanding of some fairly basic issues.

Insults only serve to diminish the credibility of your own argument.

Insults? I'm simply stating -politely - what's patently obvious.

It's an insult and you know it.

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)

On Fri, 16 Nov 2007 14:42:42 -0800 (PST), wrote
in :

On Nov 17, 8:15 am, John Navas wrote:
On Sat, 17 Nov 2007 09:10:43 +1100, "cmyk" wrote in
With all due respect, that's an essentially meaningless distinction.

(I love it! He says that, and then criticises cmyk for 'insults'.)

Fact, not an insult -- I said nothing about him personally.

So let's just stick to facts.

John, I think you cannot get better than 209 ppi from your Panasonic
at 11 x 14.

If you believe otherwise, perhaps you can show us the math? I'm happy
to be proven wrong.

You've noticed his calculation was incorrect, and you're scrambling to
save him, but it's a waste of your time, since it's still an essentially
meaningless distinction.

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)

On Fri, 16 Nov 2007 23:21:44 GMT, ClarkJohnson
wrote in :

On Sat, 17 Nov 2007 09:10:43 +1100, "cmyk" wrote:

You would do well to take time to study this instead of peremptorily dismissing it. Your response betrays a certain lack of
understanding of some fairly basic issues.

Your whole post betrays your lack of experience with reality and photography in
general. Print quality is more dependent on subject matter than it will ever do
with PPI settings.

And a difference of a few percent is totally meaningless.

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)

On Nov 17, 5:34 pm, John Navas wrote:
(nothing in factual response, which is the nearest we will get to
admission of error..)

bye

John Navas wrote:
On Fri, 16 Nov 2007 08:49:35 -1000, Scott W wrote
in :

John Navas wrote:
[SNIP]

Well I don't see how looking at the screen at %25-33% can tell you how
the print is going to look, unless you are making a very small print.
Say you start with 8MP and view at 25%, you effectively are throwing out
15 out of 16 pixels in your viewing, reducing your 8MP image down to 0.5 MP.

Viewing at 100% on screen would only be comparable to printing if your
screen had the same high resolution as the printer, but it's not even
close, as I tried to explain.

I suspect there are two quite different uses of 100% here. I suspect
by 100% you mean the image fills the screen. Whereas many image
editors take 100% to mean a pixel for pixel mapping, which with
today's cameras means that you only see a small bit of the image on
the screen, and have to scroll around to see the rest. At that kind of
100% you can see every pixel which owuld be visible on your printer,
provided of course that your eyes are good enough to see pixels. If
they aren't, many image editors allow you to magnify easily up to at
least 400%, where one camera image pixel occupies 4 screen pixels.

--
Chris Malcolm DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]

cmyk wrote:

'Pixel peeping', as you put it, is useful if you want to be able to edit the image to maximise its qualities. Even with your FZ8, a
1024x768 screen is going to downsample by a factor of 10, which really limits your ability to work with fine detail unless you zoom
in. Of course, if you're limited to a camera that only outputs jpeg files, you don't have much as scope there as you get a decent
DSLR anyway (even one with less pixels).

That's only true if the jpegs are compressed enough to suppress
detail. It's true that some cameras do that, but not all. Fine detail
involves sharp changes of colour or luminance. Jpeg compression
algorithms are built so that at higher resolution lower compressions
they can compress without losing detail. It seems to be the case that
at least one DSLR manufacturer has taken the view that since the camera
outputs RAW it's not necessary to provide good detail in the
jpegs. That also has the handy marketing consequence for those selling
RAW output cameras that it leads many people to believe that jpegs
have to be deficient in detail compared to RAW.

They don't, not if your camera is provided with the useful option to
produce high quality jpegs. I personally think a camera which doesn't
have that option is defective, even if it happens to be a DSLR.

--
Chris Malcolm DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]

"John Navas" wrote in message news
On Fri, 16 Nov 2007 23:21:44 GMT, ClarkJohnson
wrote in :

On Sat, 17 Nov 2007 09:10:43 +1100, "cmyk" wrote:

You would do well to take time to study this instead of peremptorily dismissing it. Your response betrays a certain lack of
understanding of some fairly basic issues.

Your whole post betrays your lack of experience with reality and photography in
general. Print quality is more dependent on subject matter than it will ever do
with PPI settings.

And a difference of a few percent is totally meaningless.


John,

That few percent makes *all* the difference. The practical limit for your camera with an 11x14 print is 200dpi - with the excess
pixels cropped off. The theoretical limit might be 209dpi, but can you print at 209dpi? No, the nearest you can get without
interpolation is 200dpi (and either get a slightly larger print or crop a few percent from the image dimensions)

When you send an image with data for 209dpi to a 216dpi printer, the two systems are out of phase. So the printer interpolates all
those out-of-phase pixels and the only ones that actually line up are every 209th pixel horizontally & vertically from your camera
and every 216th pixel horizontally & vertically from the printer. Everything in between is a composite made up of various
proportions of 4 adjoining pixels from your camera - if you downsample to 200dpi instead of cropping to the right pixel count for
your print size, the printer could be using parts from as many as 9 pixels from your camera.

Either way, the end is a softening of the image. True the print might look OK when printed at 216dpi - but not as good as it could
look with a bit of cropping and reprinting at 200dpi.

Maybe you should read this:
http://www.steves-digicams.com/techc...uary_2006.html
or any of the many similar articles that are readily available on the subject. Then you might actually be able to contribute
something useful to the discussion instead of digging a hole for yourself.

--
cmyk