Where are the BEST Point and Shoot Photos ?

Dave Martindale wrote:

To use a different approach to the same question, Kodak says in one of
their publications that prints are generally acceptably sharp if they
resolve 4 lp/mm on the print, and critically sharp at 8 lp/mm. Assuming
we can resolve one line pair per 2.5 pixels, 4 lp/mm requires about 250
pixels/inch, while the "critically sharp" 8 lp/mm needs 500 PPI.

8lp/mm would be in agreement with what I've seen for a 10 inch
viewing distance. But the phrase "critically sharp" is somewhat
misleading. The sensation of sharpness comes mostly from
the contrast at lower spacial frequencies. A picture can look
very "sharp" without any detail finer than 3 lp/mm.
I think "maximally detailed" would be better.

Peter.
--

On Thu, 22 Nov 2007 22:24:20 +0000 (UTC), (Dave
Martindale) wrote in :

"David J Taylor" writes:
So how is it that images on my 13 x 10.5 inch display, with all of 1.3MP,
appear perfectly sharp when viewed at 21 inches? Something to do with the
pixels being sharp?

Your monitor has a pixel pitch of about 1/100 inch. Viewed from 21
inches away, each pixel subtends about 1.6 arcmin. The finest cyclic
pattern it can display is about 18 cycles per degree. Your eye's peak
sensitivity is somewhere around 10 cycles/degree, so an image that
resolves up to 18 cycles/degree is "pretty good".

Most monitors aren't that good, more like 1/72 inch.

On the other hand, your resolution limit is about 60 cycles/degree, so
if you gradually increased the resolution of your display from 100 PPI,
you would see some improvement in the image quality until you reached
somewhere above 300 PPI. And that's at 21 inches - up close, even more
PPI would give a visible difference.

It actually maxes out below 200 PPI.

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

On Thu, 22 Nov 2007 22:12:20 +0000 (UTC), (Dave
Martindale) wrote in :

John Navas writes:

An 8x12 print under normal
viewing conditions and at normal viewing distance of 22" needs only 156
PPI for excellent results, which is only 3 MP. See
http://www.photokaboom.com/photography/learn/printing/resolution/1_which_resolution_print_size_viewing_distance.htm

There's a substantial flaw on that page!

The eye acuity page it refers to
http://www.scss.com.au/family/andrew/camera/resolution/#acuity gives
figures of 30 seconds of arc in good conditions, 1 minute of arc in
"ordinary" conditions, as the minimum separation between black lines on
a white background. That's one full cycle of the test pattern.

When converting from cycles to pixels, you have to consider how many
pixels it takes to create one black/white cycle. It takes 2 pixels as
an absolute minimum, but when you consider the effect of antialiasing
filters in real cameras you really need 2.5-3 pixels per cycle to
recreate the original pattern without aliasing artifacts at decent
contrast.

Citation? Or just your word on it?

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

John Navas writes:

"David J Taylor"
writes:
So how is it that images on my 13 x 10.5 inch display, with all of 1.3MP,
appear perfectly sharp when viewed at 21 inches? Something to do with the
pixels being sharp?

Your monitor has a pixel pitch of about 1/100 inch.

Most monitors aren't that good, more like 1/72 inch.

It doesn't matter what "most monitors" do, he provided actual numbers
for his!

Use the numbers he provided. The display has 1.3 megapixels, and is 13
x 10.5 inches. Naively using exactly those numbers, and assuming square
pixels, the pixel pitch works out to be 97.6 PPI.

On the other hand, your resolution limit is about 60 cycles/degree, so
if you gradually increased the resolution of your display from 100 PPI,
you would see some improvement in the image quality until you reached
somewhere above 300 PPI. And that's at 21 inches - up close, even more
PPI would give a visible difference.

It actually maxes out below 200 PPI.

No, it doesn't. The eye's resolution limit is about 60 cycles/degree,
and it takes *at least* 2 pixels to resolve a cycle. To achieve this at
a distance of 21 inches, you need at least 327 pixels/inch. The
calculation is

1 / (21 * tan(1/60 / 2))

If you disagree, where (exactly) do you disagree?

Dave

John Navas writes:

There's a substantial flaw on that page!

The eye acuity page it refers to
http://www.scss.com.au/family/andrew/camera/resolution/#acuity gives
figures of 30 seconds of arc in good conditions, 1 minute of arc in
"ordinary" conditions, as the minimum separation between black lines on
a white background. That's one full cycle of the test pattern.

When converting from cycles to pixels, you have to consider how many
pixels it takes to create one black/white cycle. It takes 2 pixels as
an absolute minimum, but when you consider the effect of antialiasing
filters in real cameras you really need 2.5-3 pixels per cycle to
recreate the original pattern without aliasing artifacts at decent
contrast.

Citation? Or just your word on it?

Um, what would you like a citation for?

- The statement that the page is talking about the distance between
black lines comes from the page itself, so you can read it there.

- The statement that it takes 2 pixels minimum to make one cycle of
black/white test pattern is obvious. It's also another way of restating
the Nyquist limit from sampling theory.

- The 2.5-3 pixels/cycle comes from looking at resolution charts from
real digital cameras, which achieve 0.7-0.8 of the theoretical
resolution limit. It also comes from the 0.7 value of the Kell factor
in the context of television resolution.

Note that even if you ignore the 2.5-3 "real world" factor and fall back
on the 2X theoretical limit, there's still a factor of 2 error in the
page's conclusions.

(It's also possible that the explanation is muddled, and he really means
to have the figures represent the size of half a cycle, or half the bar
pitch, or one pixel. But other references say 60 cycles/degree, and the
"cycle" terminology makes it clear that includes one white and one black
bar, or at least 2 pixels).

Dave

On Nov 23, 1:27 am, Peter Irwin wrote:
Dave Martindale wrote:

To use a different approach to the same question, Kodak says in one of
their publications that prints are generally acceptably sharp if they
resolve 4 lp/mm on the print, and critically sharp at 8 lp/mm. Assuming
we can resolve one line pair per 2.5 pixels, 4 lp/mm requires about 250
pixels/inch, while the "critically sharp" 8 lp/mm needs 500 PPI.

8lp/mm would be in agreement with what I've seen for a 10 inch
viewing distance.

That has also been my experience in good light.

But the phrase "critically sharp" is somewhat
misleading. The sensation of sharpness comes mostly from
the contrast at lower spacial frequencies. A picture can look
very "sharp" without any detail finer than 3 lp/mm.
I think "maximally detailed" would be better.

True, this can probably best be subjectively expressed as "better
textures", I think. Although that can also be improved by sharpening
(or "local contrast manipulations", if you prefer).

In article , John Navas
wrote:

On Thu, 22 Nov 2007 13:03:55 -0800, nospam wrote
in :

In article , John Navas
wrote:

Luminous Landscape rocked the photo world years ago when it demonstrated
that digital 8x10 prints from the 3.1 MP Canon D30 were actually better
than prints from high-resolution scans of the best 35 mm film, proving
in the process that 3.1 MP is all that's needed for great 8x10 prints.

that claim was very controversial back then and discounted by numerous
people.

It's actually come to be widely accepted -- it can take time for people
to accept change, but real evidence has a tendency to eventually win out
over faith and supposition.

actually it hasn't come to be widely accepted. what *has* been
accepted is that 6 mp cameras are 'about' as good as typical films,
with better fine grain films needing even higher megapixel counts to
match.

also, luminous landscape's d30 versus film comparison had different
fields of view in the two images, which gives the camera with the
cropped field of view (the d30) a huge advantage. extrapolating the
d30's 3 megapixels out to match a full frame field of view gives just
under 8 megapixels, which is consistent with other comparisons i've
seen.

http://www.luminous-landscape.com/reviews/cameras/d30/d30_vs_film.shtml

roger clark's analysis shows
otherwise, ...

Doesn't speak to the same issue, references Luminous Landscape, and
doesn't change the essential point of "3.1 MP being all that's needed
for great 8x10 prints".

it does speak to exactly the same issue and roger estimates provia with
a roughly 7-12 megapixel equivalent (figure 1) and 7 megapixels in the
table further down on the page, and those numbers even agree with what
luminous landscape found, had that comparison normalized the fields of
view.

(Dave Martindale) writes:
John Navas writes:

An 8x12 print under normal
viewing conditions and at normal viewing distance of 22" needs only 156
PPI for excellent results, which is only 3 MP. See
http://www.photokaboom.com/photography/learn/printing/resolution/1_which_resolution_print_size_viewing_distance.htm

Here is another approach entirely: Ignore web pages, ignore
textbooks, and measure your own resolution limit for yourself. Figure
out how many pixels you need before there's no point in having more.
It's not very difficult:

1. Start with a pattern of alternating black and white lines, each one
pixel wide. If you have an LCD monitor, they can be either vertical or
horizontal. For CRTs it's better if the lines are horizontal (because
CRT high frequency response limits the contrast between adjacent pixels
in the same scanline). Display this pattern on your favourite computer
monitor. Make sure that when viewed up close you have nice contrasty
clearly visible white and black alternating lines. (If you're using an
LCD monitor, set the video card resolution to match the monitor native
resolution).

2. Now move back from the monitor until the black/white line structure
vanishes completely, and the pattern now looks like uniform grey.
Measure your distance from the screen at this point. (If you need
glasses to see well at this distance, wear them - we're trying to
measure what your eyes are capable of). Call this distance D.

3. Next, figure out the size of your monitor in a direction
perpendicular to the lines you've been using. We need the size in both
physical units like inches and in pixels. If you used horizontal lines
in the pattern, measure the vertical height of the image area of your
screen. Call that H. Then determine how many pixels are currently
filling that height, which is the vertical size the video card is set
to - call that quantity P. (If you used vertical lines, measure
horizontal width and horizontal pixel count).

4. Now for the math:
The screen's pixel density is just P/H in pixels/inch or pixels/mm
depending on the units you used. Inverting that (H/P) is the pixel
pitch. At the distance D, each pixel's angular size is arctan(H/P / D).
And the reciprocal of that is the number of pixels per degree you can
see. Divide that by 2 to get cycles/degree, since it takes 2 pixels to
make one cycle in our test pattern.

For example, I just tried this using a CRT monitor. For me, without
glasses, D=50 inches, H=9.25 inches, P=960. So the monitor's pixel
density is 960/9.25 = 104 PPI, and the pixel pitch is 0.0096 inch. The
angular size of one pixel is arctan(0.0096 / 50) = 0.011 degree. The
reciprocal is 91 pixels/degree. So, with this test pattern, I can see
45 cycles/degree. That's below the textbook limit of 60 cycles/degree,
but my eyes are 50+ years old and I have some astigmatism, so I'll
believe that some people have 33% better vision than I. But now I know
my personal limit is 45 cycles/degree, at my current age (it may change
slowly).


To calculate the equivalent PPI value for "eye limited resolution" at
another distance, scale with viewing distance. If eye-limited
resolution happens at 104 PPI for my eye at 50 inches, that's equivalent
to 208 PPI at 25 inches, and 520 PPI at 10 inches. I know my eyes can
see that much detail under the right conditions. (This assumes the
print is in focus, which *would* require reading glasses at 10 inches
for me, but doesn't for the under-40 crowd with normal vision).

However, note that this is an upper bound only for the case where you
can resolve one black/white cycle with only 2 pixels. That is true of
my test pattern, and some computer-rendered images, but cameras cannot
achieve this. Digital images from cameras usually have a measured
resolution limit that is about 70-80% of the theoretical limit, which
means that the actual number of pixels required to resolve N black and
white lines is about 1.25*N to 1.35*N. If you want to make a statement
about "there's no point in printing more than X PPI because your eye
can't see it", you need to allow for this difference between pixel
count and the number of resolved lines.

And that means that, for my eyes and a viewing distance of 10 inches,
there's really no need for more than about 700 PPI.

Now, in fact, half that PPI would yield a pretty good print - this
figure simply says that there would be some visible improvement up to
about 700 PPI, but not beyond that. In practice, I'd be happy to have
400 PPI for everything, calling that "good enough", even though I know
that isn't "as good as what my eyes can see".

There are two principal differences between the calculation above and
the one that John is using to get his 156 PPI figure. First, he assumes
that viewing distance is 1.5 times image diagonal, which is plausible
for general viewing of images but not the photography enthusiast looking
at your large print. Second, the web pages he reference assume a
resolution limit of 60 pixels/degree or 30 cycles/degree, which is below
what the textbooks say, and below what my own eyes tell me. This may be
due to simple confusion between lines and line pair measurements, or
something else, but it's 2/3 of what my eyes do and 1/2 what the
textbooks say.

So, everybody go measure this for yourself!

Dave

On Fri, 23 Nov 2007 07:13:19 +0000 (UTC), (Dave Martindale)
wrote:

(Dave Martindale) writes:
John Navas writes:

An 8x12 print under normal
viewing conditions and at normal viewing distance of 22" needs only 156
PPI for excellent results, which is only 3 MP. See
http://www.photokaboom.com/photography/learn/printing/resolution/1_which_resolution_print_size_viewing_distance.htm

Here is another approach entirely: Ignore web pages, ignore
textbooks, and measure your own resolution limit for yourself. Figure
out how many pixels you need before there's no point in having more.
It's not very difficult:

1. Start with a pattern of alternating black and white lines, each one
pixel wide. If you have an LCD monitor, they can be either vertical or
horizontal.

[snipped a lot of totally useless information that would only waste bandwidth
for everyone]


So, everybody go measure this for yourself!

Dave

The next time that I want to win an award for the number of pixel wide parallel
lines that I can print, you'll be the first one I call for advice. But I think
that's already been submitted for critique to the art community in the past.
They all laughed then, they'll laugh again, I'll laugh with them. But before I
do I'll tell them that "Dave" told me this is what I'd need to be a great
photographer. He said he was RIGHT!


(See, this is the problem with people that only live in their heads and on the
internet. Totally lost touch with any reality whatsoever.)


Your resolution doesn't mean one damn thing if there's nothing in it worth
conveying. If there's something in your data worth conveying than people will
want to see it even at 640x480. Just as they will tune in a fuzzy low volume AM
radio station barely perceptible in the distance, if that was the only source
for something wonderful and new to know about. Imagine all that noise of SETI.
All it is is noise, and they're intently listening to it, hoping for, spending
their careers on, just ONE little teeny bit in all that noise that might have
some valid content. Get the idea? (I thought not.)

200,000 channels and not a damn thing worth seeing on any one of them. Isn't it
nice to know that you're just another damn useless one of them that's nothing
but more useless noise.

click

On Thu, 22 Nov 2007 22:57:43 -0800, nospam wrote
in :

In article , John Navas
wrote:

It's actually come to be widely accepted -- it can take time for people
to accept change, but real evidence has a tendency to eventually win out
over faith and supposition.

actually it hasn't come to be widely accepted.

Any proof? Or do we just have to take your word on that?

also, luminous landscape's d30 versus film comparison had different
fields of view in the two images, which gives the camera with the
cropped field of view (the d30) a huge advantage. ...

Not true, as the article makes clear.

roger clark's analysis shows
otherwise, ...

Doesn't speak to the same issue, references Luminous Landscape, and
doesn't change the essential point of "3.1 MP being all that's needed
for great 8x10 prints".

it does speak to exactly the same issue and roger estimates provia with
a roughly 7-12 megapixel equivalent (figure 1) and 7 megapixels in the
table further down on the page, and those numbers even agree with what
luminous landscape found, had that comparison normalized the fields of
view.

Not true.

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