Super-Zoom P&S Camera Beats DSLR (again) - Film at 11

On Sat, 29 Nov 2008 09:58:23 -0600, gary lawson
wrote:

No, I posted a typo correction so the moron I was trying to educate wouldn't get
hopelessly lost in his remedial kindergaten optics lessons. You didn't notice
it? Moron? I doubt that you even read any of it. Can you even read? I bet that's
been the whole problem all along. You try to sound out the words.

The whole problem all along has nothing to do with typos. It has to
do with your feeble understanding of optics and your innability to
apply the things you look up online to an argument in any coherent way
that makes sense.

"Steve" wrote in message
...

On Sat, 29 Nov 2008 08:48:00 -0600, Jasper Darnel
wrote:

On Sat, 29 Nov 2008 14:29:47 GMT, Steve wrote:


On Sat, 29 Nov 2008 03:29:09 -0600, josh pearson
wrote:

On Sat, 29 Nov 2008 09:13:06 GMT, Steve wrote:


On Sat, 29 Nov 2008 02:34:17 -0600, MackAdams
wrote:

On Sat, 29 Nov 2008 08:14:44 GMT, Steve wrote:


On Fri, 28 Nov 2008 17:33:12 -0600, NicholasWasser
wrote:

On Fri, 28 Nov 2008 20:05:37 GMT, Steve wrote:
For a typical APS-C DSLR lens, say one that opens to f/2.8 there's
a
wide range of usably sharp apertures. You can safely use from
f/3.5
all the way to f/11 and be in the "sweet spot"

Because the larger photosites on your sensor prevent you from
finding the true
"sweet spot". It can't resolve fine enough for you to know where it
is.

Yup, you really don't know what you're talking about. Now that's
obvious. The larger photosites is exactly why a DSLR's lens is
easier
to make diffraction limited than a P&S lens. It doesn't *have* to be
as sharp as a P&S lens because the pixel density is so much lower. A
P&S lens has to be a lot sharper than a DSLR lens in order for the
camera to perform as well. The fact that they are not is one reason
why you get such crappy images from P&S cameras.

LOL ... I'll let you reread that one day. You can figure out
everything that you
said wrong.

Thanks for proving you can't refute it.

For a typical P&S camera, because the pixels are so much smaller,
diffraction starts limiting your aperture much sooner and the
aperture
"sweet spot" is much less. A 10MP 1/1.8" sensor size P&S is only
good
to around f/4. f/5.6 is already becoming diffraction limited.

Try again. I don't notice strong diffraction effects until f/8.0 on
a 1/2.5"
sensor with 2.0um sized photosites (the size of the smallest grain
on good
film). Then the amount of diffraction stays the same after that.
(smaller
apertures than f/8.0) Meaning it has revealed it's true diffraction
limit. Wide
open is sharpest. Meaning, diffraction limited.

Absolutely wrong. 2um sized photosites should theoretically start to
be diffraction limited at around f/4. The fact that you don't notice
strong diffraction effects until f/8 means that your lens is softer
than it should be at wider than f/8. If you started to notice
diffraction effects at f/5.6, then your lens is diffraction limited.
Get yourself some learnin bout optiks.

A 10Mpx 1/1.8" sensor will have 2.5um sized photosites. Meaning it
won't reveal
diffraction limits as soon as f/8.0.

Let me give you a reference to clear up some of your misconceptions
and calculations, because they're wrong. There's an easy calculator
towards the bottom of this page:

http://www.cambridgeincolour.com/tut...hotography.htm

for calculating where the diffraction limit is for varios sensor
sizes, pixel counts, etc. There's also a pretty good visualization
of
aperture vs. pixel size and the airy disk superimposed over the pixel
grid.

Isn't it odd that you would quote that. That calculator's been in
error ever
since its inception. The author doesn't include physical objective
size in the
calculation nor relays to the reader that they can't tell if their
optics are
diffraction limited or not if their photosite size is too large. If a
3"
diameter DSLR lens is not diffraction limited then anything from that
calculator
is just senseless noise.

BTW: I'm more than aware of coinciding airy-disks and how they
interact. This is
what is used in astronomy with true diffraction-limited optics to
separate close
binary stars systems. This is why a 16" diameter diffraction-limited
lens can
separate them but a 4" diameter diffraction-limited one cannot. Try to
find the
"physical aperture diameter" input box in that cambrigeincolor's
calculator.
It's missing. LOL!! Someone should tell them, but it's much more fun
watching
idiots depend on other idiots for their misinformation that they
mindlessly
parrot and spew all their lives. The author of that website is another
one of
the many morons on the planet. Relaying partial misunderstood
misinformation.

You are absolutely wrong, and are only making yourself look even more
foolish... as if that were possible.

Since you claim to know so much, I'll even let you figure out yourself
why you're wrong. Look up the equation for the size of the airy disk
and tell me what it depends on. Does it depend on the physical
aperture diameter or does it depend on the f-number of the lens? Yes,
those are related, but not the same thing because just using physical
aperture diameter does not take into account the focal length. So
please tell me what the diameter of the airy disk equation is. I'll
give you a hint:

D = 2.43932 * wavelength * _______

I'll even give you multiple choices for the blank. a) physical
aperture diameter. b) f-number.

When you figure out which of the multiple choices above is right,
you'll realize why what you're saying above is wrong.

I'll let some other reader enjoy the rest of your misinformed
diatribe... I have
better things to do...

Sure, like spreading your misinformed diatribe.

Steve

Get back to me when you've educated yourself enough. I'm not here to
play your
remedial tutor for free.

Translation - you finally realized why you're an idiot. Thank you.
Point proven.

Since you're still in optics-kindergarten and you love nothing better than
running around the room like a screaming brat, banging your head against
the
walls just to see if you can get anyone's attention, I feel nothing but
pity for
you. Because of that I'll give you one phrase to study until the next time
that
you deserve a lesson -- "Dawe's limit"

(next time = never)

Go get a life and a brain you ****in' useless moronic troll.

You're a complete and total waste of flesh. Someone should put you out of
everyone's misery that you create for everyone on this planet.

Thanks again for proving to everyone that you're an absolute stupid
moronic troll who knows nothing about optics. Dawe's limit only
applies to the theoretical max resolving limit when not stopped down.
Once you start stopping down a lens with a variable aperture, the
formula for Dawe's limit, which depends only on the size of the
objective, no longer applies. It's used for telescopes and
microscopes, where you wouldn't want to stop down a lens like you
would a camera.


Dawes limit is applicable to camera lenses, which would also be diffraction
limited and usable wide open if they were capable of making them diffraction
limited. But making a telescope with a 100mm wide objective and and f8
focal ratio diffraction-limited is much easier than some superzoom with an
f4 max aperture. Because you have to stop them down to achieve top optical
performance means most (if not all) camera lenses are not
diffraction-limited.
But the fact remains that P&S optics are huge compromises whose aberrations
are visible in nearly every shot, even if they are stopped down.

On Sat, 29 Nov 2008 13:00:02 -0500, "RichA"
wrote:


"Steve" wrote in message
.. .

On Sat, 29 Nov 2008 08:48:00 -0600, Jasper Darnel
wrote:

On Sat, 29 Nov 2008 14:29:47 GMT, Steve wrote:


On Sat, 29 Nov 2008 03:29:09 -0600, josh pearson
wrote:

On Sat, 29 Nov 2008 09:13:06 GMT, Steve wrote:


On Sat, 29 Nov 2008 02:34:17 -0600, MackAdams
wrote:

On Sat, 29 Nov 2008 08:14:44 GMT, Steve wrote:


On Fri, 28 Nov 2008 17:33:12 -0600, NicholasWasser
wrote:

On Fri, 28 Nov 2008 20:05:37 GMT, Steve wrote:
For a typical APS-C DSLR lens, say one that opens to f/2.8 there's
a
wide range of usably sharp apertures. You can safely use from
f/3.5
all the way to f/11 and be in the "sweet spot"

Because the larger photosites on your sensor prevent you from
finding the true
"sweet spot". It can't resolve fine enough for you to know where it
is.

Yup, you really don't know what you're talking about. Now that's
obvious. The larger photosites is exactly why a DSLR's lens is
easier
to make diffraction limited than a P&S lens. It doesn't *have* to be
as sharp as a P&S lens because the pixel density is so much lower. A
P&S lens has to be a lot sharper than a DSLR lens in order for the
camera to perform as well. The fact that they are not is one reason
why you get such crappy images from P&S cameras.

LOL ... I'll let you reread that one day. You can figure out
everything that you
said wrong.

Thanks for proving you can't refute it.

For a typical P&S camera, because the pixels are so much smaller,
diffraction starts limiting your aperture much sooner and the
aperture
"sweet spot" is much less. A 10MP 1/1.8" sensor size P&S is only
good
to around f/4. f/5.6 is already becoming diffraction limited.

Try again. I don't notice strong diffraction effects until f/8.0 on
a 1/2.5"
sensor with 2.0um sized photosites (the size of the smallest grain
on good
film). Then the amount of diffraction stays the same after that.
(smaller
apertures than f/8.0) Meaning it has revealed it's true diffraction
limit. Wide
open is sharpest. Meaning, diffraction limited.

Absolutely wrong. 2um sized photosites should theoretically start to
be diffraction limited at around f/4. The fact that you don't notice
strong diffraction effects until f/8 means that your lens is softer
than it should be at wider than f/8. If you started to notice
diffraction effects at f/5.6, then your lens is diffraction limited.
Get yourself some learnin bout optiks.

A 10Mpx 1/1.8" sensor will have 2.5um sized photosites. Meaning it
won't reveal
diffraction limits as soon as f/8.0.

Let me give you a reference to clear up some of your misconceptions
and calculations, because they're wrong. There's an easy calculator
towards the bottom of this page:

http://www.cambridgeincolour.com/tut...hotography.htm

for calculating where the diffraction limit is for varios sensor
sizes, pixel counts, etc. There's also a pretty good visualization
of
aperture vs. pixel size and the airy disk superimposed over the pixel
grid.

Isn't it odd that you would quote that. That calculator's been in
error ever
since its inception. The author doesn't include physical objective
size in the
calculation nor relays to the reader that they can't tell if their
optics are
diffraction limited or not if their photosite size is too large. If a
3"
diameter DSLR lens is not diffraction limited then anything from that
calculator
is just senseless noise.

BTW: I'm more than aware of coinciding airy-disks and how they
interact. This is
what is used in astronomy with true diffraction-limited optics to
separate close
binary stars systems. This is why a 16" diameter diffraction-limited
lens can
separate them but a 4" diameter diffraction-limited one cannot. Try to
find the
"physical aperture diameter" input box in that cambrigeincolor's
calculator.
It's missing. LOL!! Someone should tell them, but it's much more fun
watching
idiots depend on other idiots for their misinformation that they
mindlessly
parrot and spew all their lives. The author of that website is another
one of
the many morons on the planet. Relaying partial misunderstood
misinformation.

You are absolutely wrong, and are only making yourself look even more
foolish... as if that were possible.

Since you claim to know so much, I'll even let you figure out yourself
why you're wrong. Look up the equation for the size of the airy disk
and tell me what it depends on. Does it depend on the physical
aperture diameter or does it depend on the f-number of the lens? Yes,
those are related, but not the same thing because just using physical
aperture diameter does not take into account the focal length. So
please tell me what the diameter of the airy disk equation is. I'll
give you a hint:

D = 2.43932 * wavelength * _______

I'll even give you multiple choices for the blank. a) physical
aperture diameter. b) f-number.

When you figure out which of the multiple choices above is right,
you'll realize why what you're saying above is wrong.

I'll let some other reader enjoy the rest of your misinformed
diatribe... I have
better things to do...

Sure, like spreading your misinformed diatribe.

Steve

Get back to me when you've educated yourself enough. I'm not here to
play your
remedial tutor for free.

Translation - you finally realized why you're an idiot. Thank you.
Point proven.

Since you're still in optics-kindergarten and you love nothing better than
running around the room like a screaming brat, banging your head against
the
walls just to see if you can get anyone's attention, I feel nothing but
pity for
you. Because of that I'll give you one phrase to study until the next time
that
you deserve a lesson -- "Dawe's limit"

(next time = never)

Go get a life and a brain you ****in' useless moronic troll.

You're a complete and total waste of flesh. Someone should put you out of
everyone's misery that you create for everyone on this planet.

Thanks again for proving to everyone that you're an absolute stupid
moronic troll who knows nothing about optics. Dawe's limit only
applies to the theoretical max resolving limit when not stopped down.
Once you start stopping down a lens with a variable aperture, the
formula for Dawe's limit, which depends only on the size of the
objective, no longer applies. It's used for telescopes and
microscopes, where you wouldn't want to stop down a lens like you
would a camera.


Dawes limit is applicable to camera lenses, which would also be diffraction
limited and usable wide open if they were capable of making them diffraction
limited. But making a telescope with a 100mm wide objective and and f8
focal ratio diffraction-limited is much easier than some superzoom with an
f4 max aperture. Because you have to stop them down to achieve top optical
performance means most (if not all) camera lenses are not
diffraction-limited.
But the fact remains that P&S optics are huge compromises whose aberrations
are visible in nearly every shot, even if they are stopped down.

Dawe's limit is only applicable to camera lenses when they are not
stopped down. Once you start stopping down a camera lens, Dawe's
limit no longer works. Proof of that is as simple as looking at the
equation and seeing what it does when you stop down a camera lens.

Dawe's limit says that R = 4.56/D where R is the angular resolution in
arcseconds and D is the objective diameter in inches. When you stop
down a lens, you're not changing D. But you are changing R. So the
formula no longer applies. For example, let's take a lens with a 3"
objective. Dawe's limit says the max resoluion is 1.52 arcseconds.
Now, stop it down to f/64. If you were to say that Dawe's limit still
applies, you'd say that the max resolution is still 1.52 arcseconds.
But it's not, because of diffraction.

Dawe's limit is good for telling you wheter a particular lens is
diffraction limited or not. Despite what our resident P&S troll
claims, in practice, camera lenses are not diffration limited. Well,
at least not any that an average photographer can afford to use.
Because they all have certain aberrations that make the circle of
uncertainty larger than the airy disk when it's wide open.

So realizing that fact, you can get back to concentrating on the point
of the discussion, which is what diffraction does to a real camera
with real pixels of a certain size and a real lens stopped down to a
certain aperture. For that, you would use the simplified equation for
the size of the airy disk (D=2.44*wavelength*f-numer) and see if it's
larger or smaller than around twice the pixel size at a particular
aperture.

And I say simplified because the actual size can not be expressed by a
simple equation. But for our purposes, where you're talking about big
jumps in aperture like from f/4 to f/5.6 and not trying to nail it
down to something like f/4.32442, the simplified equation is more than
adequate. You're also making other assumptions, like the wavelength
varies light across the spectrum, the aperture is not circular, the
pixels might not be square (like Nikon APS-C).

But all those assumption and simplifications are not enough to change
the results when you don't care about an exact aperture where
diffraction starts becoming a problem and are satisfied with
"somewhere between f/4 and f/5.6" or "somewhere between f/11 and f/16"

There's another thing our resident P&S troll doesn't understand and
why he claims the diffraction calculater at
http://www.cambridgeincolour.com/tut...hotography.htm
is wrong because it doesn't take the objective or physical aperture
size into account. It's not inaccurate. It's just not as precise as
it could be. And if you don't know the difference between accuracy
and precision, look it up. But it doesn't *have* to have the added
precision gains by using a more complex equation for the airy disk
size because the selected aperture is given in stops, not a continuous
range, and only has 2 significant figures in the selected values.

Steve

"Steve" wrote in message
...

Dawe's limit says that R = 4.56/D where R is the angular resolution in
arcseconds and D is the objective diameter in inches. When you stop
down a lens, you're not changing D. But you are changing R.

Of course you are changing D. If you weren't, it would be possible to
improve the performance of a lens by adding glass outside the entrance
pupil, even though that glass does not affect the image in any way because
no light passes through it.

For the purpose of computing the Dawes limit, D should be the diameter of
the entrance pupil, which in turn is equal to the focal length divided by
the f-stop.

On Sat, 29 Nov 2008 19:42:19 GMT, "Andrew Koenig" wrote:

Of course you are changing D. If you weren't, it would be possible to
improve the performance of a lens by adding glass outside the entrance
pupil, even though that glass does not affect the image in any way because
no light passes through it.

Yes, which is my point. By doing that, you are effectively stopping
down the lens with an aperture right behind the objective.

For the purpose of computing the Dawes limit, D should be the diameter of
the entrance pupil, which in turn is equal to the focal length divided by
the f-stop.

Which is again what I was trying to say, but maybe not succeeding.
Maybe better to say that *if* you use the diameter of the objective
lens in Dawe's equation, then it does not work as you stop down the
lens.

Steve

"Steve" wrote in message
...

Of course you are changing D. If you weren't, it would be possible to
improve the performance of a lens by adding glass outside the entrance
pupil, even though that glass does not affect the image in any way because
no light passes through it.

Yes, which is my point. By doing that, you are effectively stopping
down the lens with an aperture right behind the objective.

OK, so we agree.

For the purpose of computing the Dawes limit, D should be the diameter of
the entrance pupil, which in turn is equal to the focal length divided by
the f-stop.

Which is again what I was trying to say, but maybe not succeeding.
Maybe better to say that *if* you use the diameter of the objective
lens in Dawe's equation, then it does not work as you stop down the
lens.

OK, so we still agree, or so I believe. I think we are both saying that
when you try to apply the Dawes equation (as far as I know, the s in "Dawes"
is part of the person's name, not a possessive) R = 4.56/D, the value you
should use for D is the value of the entrance pupil, not the physical
diameter of the lens.

The entrance pupil changes as you stop down the lens; the physical diameter
obviously does not. Accordingly, stopping down a lens changes R, even
though the physical size of the lens does not change.

And it is important to use the diameter of the entrance pupil, *not* the
diameter of the diaphragm; because these two diameters can differ
dramatically when there are strongly curved elements between the entrance
pupil and the subject.

On Sat, 29 Nov 2008 20:04:01 GMT, "Andrew Koenig" wrote:

For the purpose of computing the Dawes limit, D should be the diameter of
the entrance pupil, which in turn is equal to the focal length divided by
the f-stop.

Which is again what I was trying to say, but maybe not succeeding.
Maybe better to say that *if* you use the diameter of the objective
lens in Dawe's equation, then it does not work as you stop down the
lens.

OK, so we still agree, or so I believe. I think we are both saying that
when you try to apply the Dawes equation (as far as I know, the s in "Dawes"
is part of the person's name, not a possessive) R = 4.56/D, the value you

Right, thanks for correcting me. I guess it would be more correctly
Dawes' limit.

should use for D is the value of the entrance pupil, not the physical
diameter of the lens.

The entrance pupil changes as you stop down the lens; the physical diameter
obviously does not. Accordingly, stopping down a lens changes R, even
though the physical size of the lens does not change.

And it is important to use the diameter of the entrance pupil, *not* the
diameter of the diaphragm; because these two diameters can differ
dramatically when there are strongly curved elements between the entrance
pupil and the subject.

Yup, we agree. The main application I ever use the equation for is
for telescopes where you don't have to worry about things like
stopping down a lens. For instance, my Criterion Dynascope RV-6
newtonian reflector has a D of 6" and that doesn't change. And I'm
never going to stop it down. The f-number is fixed at f/8 (actually
f/8.3 for mine.) Of course the exit pupil can vary depending on the
eyepiece focal length.

Steve

Andrew Koenig wrote:
"John A." wrote in message

I must say, though, that while from a "winning the argument" point of
view arguing against a troll is pointless, ...

The following proverb may be relevant he

Never try to teach a pig to sing.
It wastes your time and annoys the pig.

Perhaps more apropros...

Never mud wrestle with a pig:
You both get dirty and the pig likes it.

--
Ray Fischer

"Steve" wrote in message
...

Yup, we agree. The main application I ever use the equation for is
for telescopes where you don't have to worry about things like
stopping down a lens.

Actually, you sometimes do. Consider, for example, the Questar 3.5-inch
Maskutsov telescope. As normally shipped, that scope comes with a solar
filter that has a diameter of only 1.5 inches. The usable part of the
filter is actually off-center, so it doesn't overlap the silvered spot in
the middle of the corrector plate.

So when you are using that filter, the effective aperture of the telescope
is only 1.5 inches and its resolution is decreased accordingly.

Of course, its resolution is also decreased by the air turbulence that
invariably results during the day, which is when you'd be trying to look at
the sun anyway :-)

Never mud wrestle with a pig:
You both get dirty and the pig likes it.

I can't resist.

A tourist was walking by an apple orchard, and came across a farmer standing
on a ladder next to an apple tree, holding a pig in his arms.

"What are you doing?" asked the tourist.

"I'm feeding my pig." said the farmer. "I'm holding him up in the tree so he
can eat apples from the branches."

"Why not put the pig on the ground and shake the tree? That way the apples
would fall from the tree and the pig could eat them off the bround."

"What would be the advantage of doing that?"

"It would save a lot of time."

"That may be true," said the farmer, "but what is time to a pig?