Telephoto Reach and Digital Cameras - lens comparison

"Roger N. Clark (change username to rnclark)" username@qwest.
net wrote:
Dudley Hanks wrote:

Before all you purists post your kindly admonishments that I
am confusing diffraction and refraction, let me just poinht
out that the two concepts are, shall we say, at worst rather
inter-related...

Dudley,
They are related in that both processes change the direction
that light travels.


If the resolving power of a circular lens were only impacted
by the "diffraction" effect of waves passing around / by
obstacles, how would polishing it to a micro level make any
difference?

I view refraction as, more or less, an extension / subset of
diffraction; I'm not sure how well that goes over with the
more academic scientific community.

It really is two different processes, and they generally work
in the opposite direction with glass lenses over the visible
spectrum. Shorter wavelengths are bent more as the light
passes through a glass lens. Diffraction affects longer
wavelengths more (red light).

But the role of polishing has little to do with diffraction performance
of a lens over the visible spectrum. Good polishing generally reduces
flare, but doesn't make the lens diffraction limited. The figure of
the polished lens has more to do with that, along with a multi-element
design to reduce chromatic and other aberrations.

So we all know who is wrong again.

Roger.



As I've said in the past, my background in photography has
sorely lacked in academics, so I'll take advantage of this
thread to gain a bit of a foothold in optics...


I've tried looking up info on diffraction limited lens
configurations in the past, but the mathematics are a bit
tricky for me as I can't see the math symbols, myself.
Instead, I rely on my screen reader to tell me what's there.
Unfortunately, most screen readers don't do a good job with
special symbols, leaving me to wonder a bit about what the
math actually is, respecting diffraction limiting.


To my reader, the Wikipedia article about the subject comes
across looking (sounding) like this:

The ability of an imaging system to resolve detail is
ultimately limited by diffraction. This is because a plane
wave incident on a circular lens or mirror is diffracted as
described above. The light is not focused to a point but forms
an Airy disk having a central spot in the focal plane with
radius to first null of d = 1.22 \lambda N,\, where ? is the
wavelength of the light and N is the f-number (focal length
divided by diameter) of the imaging optics. In object space,
the corresponding angular resolution is \sin \theta = 1.22 \
frac{\lambda}{D},\, where D is the diameter of the entrance
pupil of the imaging lens (e.g., of a telescope's main mirror)
.. Two point sources will each produce an Airy pattern – see
the photo of a binary star. As the point sources move closer
together, the patterns will start to overlap, and ultimately
they will merge to form a single pattern, in which case the
two point sources cannot be resolved in the image. The
Rayleigh criterion specifies that two point sources can be
considered to be resolvable if the separation of the two
images is at least the radius of the Airy disk, i.e. if the
first minimum of one coincides with the maximum of the other.


Thus, the larger the aperture of the lens, and the smaller the
wavelength, the finer the resolution of an imaging system.
This is why telescopes have very large lenses or mirrors, and
why optical microscopes are limited in the detail which they
can see.
[
Now, I think my translation is lacking a bit, so I'm wondering
if you might be able to point me towards a description of the
math which does not rely on symbols, but rather describes it
verbally?

It is interesting to note that this description, even if one
cannot follow the math, pretty clearly states that size is of
primary importance.

Would appreciate any advice you can pass my way, Roger.


Take Care,
Dudley

Superzooms Still Win wrote:
On Fri, 17 Dec 2010 01:06:43 -0800, bobwilliams wrote:

I admire Roger's contributions to this newsgroup and take all his
data, images and conclusions very seriously.
Bob

Then you are a fool. He poses BAD SCIENCE as a way to get controversy so
people visit his website where he then tries to sell his ****-poor tourists
crapshots. He's that desperate for anyone to see his photography because
nobody wants to. It's his only motive and method. His calculations have
been proved wrong so many times in the past that people just stopped
bothering to correct all his errors. Then idiots like you fall for his
bull**** song and dance.

If am a fool, then I am in good company in this NG.
Roger posts a lot of Quantitative data that are not available anywhere
else. I use them a lot.

Some of his photos are awesome.
This shot of an egret won first prize against International competition
in NATURE'S BEST Magazine. This magazine is the premier Nature
Photography Magazine in the world. I have been a subscriber for many
years and you will not find any touristy snapshots in this Magazine.
See:
http://www.clarkvision.com/galleries...ght.f-600.html


Hey! We can all agree to disagree on some topics and still stay friends.
Actually, life would be pretty dull if we all agreed on everything.
But disagreeing with someone does not, de facto, make them a fool, idiot
or moron.
To fracture Shakespeare a little, "Methinks thou doth protest too much".
Bob Williams

On 12/18/2010 4:12 AM, bobwilliams wrote:
snip

Some of his photos are awesome.
This shot of an egret won first prize against International competition
in NATURE'S BEST Magazine. This magazine is the premier Nature
Photography Magazine in the world. I have been a subscriber for many
years and you will not find any touristy snapshots in this Magazine.
See:
http://www.clarkvision.com/galleries...ght.f-600.html


Hey! We can all agree to disagree on some topics and still stay friends.
Actually, life would be pretty dull if we all agreed on everything.
But disagreeing with someone does not, de facto, make them a fool, idiot
or moron.
To fracture Shakespeare a little, "Methinks thou doth protest too much".
Bob Williams

Bob, thanks for posting the link to Roger's awesome photo. Obviously he
knows something about photography. Does SSW?
Allen

Ofnuts wrote:
Superzooms Still Win wrote:

As for your physics proving everything, it FAILS because it does NOT take
into account the figure of the lenses. The lenses on the superzoom camera
can and ARE polished to diffraction-limited quality.

Yes, they are polished to diffraction-limited quality at the top of a
high moutain by virgin girls under the full moon. They are then laid on
silk cushions and brought back in the valley using buffalo carts, and
the tiny moves of the lenses on the cushions caused by the gentle
rocking of the cart finishes the polishing to perfection.

Panasonic's Leica lenses are finished off wrapped in silk between Swiss
virgin's breasts trotting on horseback down the mountain as they sing
the praises of their fine accuracy and innovative engineering;
instilling emotional warmth, impact, and subtlety.
http://www2.panasonic.com/webapp/wcs...tGroupId=24999

Dudley Hanks wrote:

As I've said in the past, my background in photography has
sorely lacked in academics, so I'll take advantage of this
thread to gain a bit of a foothold in optics...

I've tried looking up info on diffraction limited lens
configurations in the past, but the mathematics are a bit
tricky for me as I can't see the math symbols, myself.
Instead, I rely on my screen reader to tell me what's there.

I don't think the math matters that much or the intricate details of
diffraction patterns for the purposes of this discussion it's fine to
just think of it as the smallest detail that can be resolved for a given
aperture.

Refraction just means bending light through glass versus a reflecting
mirror lens or telescope. Mirror lenses avoid chromatic aberrations
because there is no refracting through the glass, so no rainbow color
fringing. Aberrations are what matters in this discussion; like color
fringes, corner softness, barrel, pincushion, vignetting and the like.
Those are determined by the design of the lens (figure/shape) and how
multiple elements combine to correct for these aberrations.

Smooth sub-micron tolerance is just how precisely the final product
matches the design. If quality control isn't up to snuff, you'll get
random blurry splotches across the frame, or just overall softness. SZ
claims the smaller size of lens elements allows being more precise since
you don't have a huge hunk of glass to work on... I'm not sure there's
much to that argument. There are a few specialty 35mm lenses with large
aspherical shaped elements, meaning it's parabolic and can't just be
ground in a simple round jig but needs more hand holding. These can show
more variation in the hand work and are a lot of money because it takes
more time and care. But those are rare, I believe modern lenses tend to
use smaller aspheric plastic elements or moulded vs ground. Computers
allow designing more complex solutions.

Anyways, back to the point here. Diffraction limited I think generally
refers to the optical design's control of aberrations such that the
aberrations are so slight that the diffraction degrades the image before
the aberrations do. If a lens is not diffraction limited, stopping down
will improve image quality because those refraction aberrations mostly
improve when stopping down. That effect is complex to explain but it
generally works that way. Faster lenses are harder to design because of
these aberrations, slow lenses easier.

The sub-micron tolerance thing wouldn't be effected by stopping down.


Now some more abstract comparisons, I suspect the reason you don't see
super fast P&S lenses with shallow DOF is the exact same reason they
cost a lot in 35mm format. P&S are designed for economy and it would be
too expensive to grind lenses that small to such tolerance;
unmarketable. Now I'm talking '35mm equivalent aperture' which is a
concept with little acceptance but it's valid if you want shallow DOF.
If you just scale down a 50mm f/1.4 lens to fit a P&S, it would still be
f/1.4 but there would be more DOF which means you'd need to redesign it
as something like 10mm f/0.7, and that is going to be a very difficult
thing to design; the faster the lens, the worse the aberrations get.
There are microscope objectives in that category of performance which
are a pretty good estimation of what you'd need to make a nice fast P&S
lens. A really nice fast apochromatic microscope objective costs about
$5000. Apochromatic means not just the red green chromatic aberration is
corrected in the design but another level or more like blue/yellow or
specific attention to UV, etc. That's the kind of design needed for
'diffraction limited' and I never heard of such a thing in a super zoom
compact.

Dudley Hanks wrote:

To my reader, the Wikipedia article about the subject comes
across looking (sounding) like this:

The ability of an imaging system to resolve detail is
ultimately limited by diffraction. This is because a plane
wave incident on a circular lens or mirror is diffracted as
described above. The light is not focused to a point but forms
an Airy disk having a central spot in the focal plane with
radius to first null of d = 1.22 \lambda N,\, where ? is the
wavelength of the light and N is the f-number (focal length
divided by diameter) of the imaging optics. In object space,
the corresponding angular resolution is \sin \theta = 1.22 \
frac{\lambda}{D},\, where D is the diameter of the entrance
pupil of the imaging lens (e.g., of a telescope's main mirror)
. Two point sources will each produce an Airy pattern – see
the photo of a binary star. As the point sources move closer
together, the patterns will start to overlap, and ultimately
they will merge to form a single pattern, in which case the
two point sources cannot be resolved in the image. The
Rayleigh criterion specifies that two point sources can be
considered to be resolvable if the separation of the two
images is at least the radius of the Airy disk, i.e. if the
first minimum of one coincides with the maximum of the other.

Dudley,

The relevant equation above is

Diffraction spot diameter = 2 * 1.22 w * f / D = 2.44 * w * f_ratio,

where w = wavelength, f = focal length, D = aperture diameter,
and f_ratio is the f/ratio of the optical system.
So if you specify wavelength of light in microns, the diffraction
spot diameter is in microns.

The diffraction spot size for green light of 0.53 microns
(5300 angstroms) is:

f/2: 2.6 microns,
f/4: 5.2 microns,
f/8: 10.3 microns.

The above from:
http://www.clarkvision.com/articles/...ml#diffraction

So you see that cameras with small pixels (P&S cameras typically
have pixels under 2 microns, and superzoom cameras with f/4 and
slower lenses thus have pixels much smaller than the diffraction
diameter.

But more important is resolution on the subject. With more real
focal length, the diffraction spot becomes a smaller angular diameter
if you keep f/ratio the same. That is because the diameter of the
aperture is getting larger. So the longer focal lengths
found in DSLR telephotos provides proportionally greater
resolution on a subject.

Resolution on a subject is given by:
resolution = constant / lens diameter,
where the constant is determined by the wavelength.

The Dawes limit is the limit at which no more detail on a subject
can be resolved, or in other words, zero contrast on closely
spaced detail, like line pairs in a test target, or hairs on an
animal.

e.g.:
http://en.wikipedia.org/wiki/Dawes'_limit

resolution in arc-seconds = 4.56 /D where D is the clear aperture in inches
and the 4.56 is for a particular wavelength (green light).
With D on the bottom of the equation, the finest detail one can
resolve goes down as the lens aperture goes up. That dictates
the fundamental difference between P&S superzoom cameras and
DSLRs, and the field of view lens multiplier is now a great
confusing factor among photographers selecting digital cameras.

Roger



Thus, the larger the aperture of the lens, and the smaller the
wavelength, the finer the resolution of an imaging system.
This is why telescopes have very large lenses or mirrors, and
why optical microscopes are limited in the detail which they
can see.
[
Now, I think my translation is lacking a bit, so I'm wondering
if you might be able to point me towards a description of the
math which does not rely on symbols, but rather describes it
verbally?

It is interesting to note that this description, even if one
cannot follow the math, pretty clearly states that size is of
primary importance.

Would appreciate any advice you can pass my way, Roger.


Take Care,
Dudley

Paul Furman wrote:

Now some more abstract comparisons, I suspect the reason you don't see
super fast P&S lenses with shallow DOF is the exact same reason they
cost a lot in 35mm format. P&S are designed for economy and it would be
too expensive to grind lenses that small to such tolerance;
unmarketable. Now I'm talking '35mm equivalent aperture' which is a
concept with little acceptance but it's valid if you want shallow DOF.
If you just scale down a 50mm f/1.4 lens to fit a P&S, it would still be
f/1.4 but there would be more DOF which means you'd need to redesign it
as something like 10mm f/0.7,

Paul,
If the crop multiplier is 5x, so the 10mm lens on the P&S is the
same as the 50 mm lens on the 35mm sized sensor, the aperture
diameter must be maintained for the same depth of field. Thus
the 50 mm f/1.4 becomes 1.4/5 = f/0.28 on the 10 mm lens, which
is pretty much impossible to build.

Roger

On Fri, 17 Dec 2010 08:00:05 -0700, "Roger N. Clark (change username to
rnclark)" c wrote:

Superzooms Still Win wrote:
On Wed, 15 Dec 2010 08:39:38 -0700, "Roger N. Clark (change username to
wrote:

Superzooms Still Win wrote:
On Wed, 15 Dec 2010 01:25:07 -0600, Dudley Hanks
wrote:

Now that Roger has debunked your claims about detail, LOL,

perhaps we should run an analysis of the number of colour
shades captured in those DSLR and P&S pics? Or, are you still
smarting from the butterfly drubbing you took ... ?

But but DUDley! Didn't you compare that other image I posted that showed
many many thousands of more color shades in its data so therefore it MUST
be a better image according to your reasoning? What? Didn't you show it to
your sighted friends so they could laugh out loud at your absurdity and
failed reasoning? Didn't you even show them how your "editing skills"
totally trashes every photo you put through your "enhancing" routines?
We've all seen it, that's why they were all remaining so silent, you were
making such a total fool of yourself, AGAIN.

You are not getting it. Simple physics proves you are wrong.
Regarding image detail, the super zoom P&S cameras have clear
apertures on the order of an inch or less. Diffraction from
such a small lens means poor subject resolution. A DSLR with
even a lower end fixed telephoto like 300 f/4 has about a 3-inch
clear aperture, thus on the order of 3x higher resolution
on a subject. The 3x larger diameter lens delivers 9x
more light. More light = finer gradations due to better
signal-to-noise ratio. Again, this is simple physics.
There is no contest between a DSLR versus P&S whether telephoto
resolution on a subject or color tonality, or signal-to-noise
ratio. Simple physics, the DSLR wins. Anyone who can do
simple physics can prove this. Dudley is correct.

Roger

Hey MORON, this has nothing to do with lens physics, DUDley is throwing in
another situation that he created which proved himself too to be a total
moron.

You are wrong. It has to do with both lens physics and sensor
physics. Conisder two cameras, one with double the sensor size,
double the lens focal length, and double the pixel size, and the same
f/ratio lens. The lens has 4 times the area so collects 4 times the
light. The sensors have the same spatial resolution, but the larger
pixels collect 4 times the light from the lens delivering 4 times the
light. The signal-to-noise ratio is double on the large sensor camera.
The higher signal-to-noise ratio delivers finer tonality and greater
dynamic range. This is well proven and simple physics.


Again, you prove yourself to be a total MORON. DUDley was NOT referring to
your optics bull****, he was referring to his OWN bull**** where he
believes that more individual colors in an image file means its a better
image (wha' what?!? yep, he's that ****ingly stupid). Something that is
totally unrelated to the crap that you are spewing. Thus proving yet again,
just how ****ingly blind and ignorant that you are as well.

LOL. This is priceless, the main person in support of you is a blind-man
who doesn't even comprehend the main concepts of optics and photography.
This says so much about you. Truly a case of the blind leading the blind.
ROFLMAO!


As for your physics proving everything, it FAILS because it does NOT take
into account the figure of the lenses. The lenses on the superzoom camera
can and ARE polished to diffraction-limited quality. They have to be in
order to allow the photosites resolve individual details. Otherwise nobody
would buy them. Thereby allowing them to have more resolution at larger
apertures. DSLR glass is NEVER ground to diffraction-limited quality,
because the cost to do so puts them outside the reach of every consumer,
therefore they can never attain diffraction-limited resolutions at ANY
useful aperture.

What a laugh! Physics does very well. Again it is simple physics
that shows that the big lenses with DSLRs doesn't even need to be close
to diffraction limited in other to deliver better resolution on a subject
compared to the tiny lenses on P&S super zoom cameras.
Simple physics proves it.

But then you already knew this, or you wouldn't have blatantly biased your
fools' tests again by choosing aperture and exposure settings and
resolutions and JPG compressions which would give an advantage to your
PIECE OF **** DSLR CRAP.

Shove that "physics" up your useless asshole full of relentless BAD-SCIENCE
bull****. Now, go ahead, spend three more years of your useless life trying
to outdo more P&S cameras that have already surpassed anything you have
ever accomplished in your miserable existence.

Simple equation:
Dawes limit = 5.45/D where D=lens clear aperture diameter.
You can try shoving the physics wherever you want to but it won't
change the basic and well understood laws of physics.

Simple physics proves you wrong.
QED

Roger

What a shame, that I have more important things to do than correct all your
bull**** for you again. When you start paying me to be your teacher perhaps
I'll bother.

But here's a freebie for you anyway: Diffraction artifacts are also a
function of distance. I bet you can't figure out why that too can so easily
prove you completely wrong yet again. As if your glaring omission of lens
figures wasn't enough, and still you refuse to see your crippled reasoning.
But don't let me stop you from being the #1 fool of the photography and
science communities. You do it so well on your own. Without idiots like you
spewing your laughable results from your botched and blatantly biased tests
there'd be so fewer laughs in the world.

On Sat, 18 Dec 2010 02:12:50 -0800, bobwilliams wrote:

Superzooms Still Win wrote:
On Fri, 17 Dec 2010 01:06:43 -0800, bobwilliams wrote:

I admire Roger's contributions to this newsgroup and take all his
data, images and conclusions very seriously.
Bob

Then you are a fool. He poses BAD SCIENCE as a way to get controversy so
people visit his website where he then tries to sell his ****-poor tourists
crapshots. He's that desperate for anyone to see his photography because
nobody wants to. It's his only motive and method. His calculations have
been proved wrong so many times in the past that people just stopped
bothering to correct all his errors. Then idiots like you fall for his
bull**** song and dance.

If am a fool, then I am in good company in this NG.
Roger posts a lot of Quantitative data that are not available anywhere
else. I use them a lot.

Some of his photos are awesome.
This shot of an egret won first prize against International competition
in NATURE'S BEST Magazine. This magazine is the premier Nature
Photography Magazine in the world. I have been a subscriber for many
years and you will not find any touristy snapshots in this Magazine.
See:
http://www.spamvision.com/galleries/...ght.f-600.html


BFD, even a stopped-clock is right twice a day. Quite frankly I'm suspect
of whoever judged that improperly exposed and poorly composed zoo snapshot.
I've posted ones better than that as throw-aways here just for examples to
prove all these trolls wrong on issues unrelated to marketable photography.

I stopped entering international competitions when I found out how easy
they were to win. There's no challenge in winning awards. One time I
entered a purposely crappy photo just as a joke, to show all my
photographer friends just what kind of crap-photography will win an award.
They bet me it would never win. I said, "Wait and watch. They'll actually
vote on this crap." It won. It was a good laugh. This says so much more
about the viewer and voter than it does any photographer. One need only see
the praises handed out on Flickr to comprehend the folly of it all.

On Sat, 18 Dec 2010 13:20:03 -0600, Superzooms Still Win
wrote:

BFD, even a stopped-clock is right twice a day. Quite frankly I'm suspect
of whoever judged that improperly exposed and poorly composed zoo snapshot.
I've posted ones better than that as throw-aways here just for examples to
prove all these trolls wrong on issues unrelated to marketable photography.

You've never posted a link to one of your images that would be
accepted by one of those neighborhood free papers, let alone a real
publication. Unless, of course, there's a magazine called "The Rare
Moth Review" that prints fuzzy, poorly-composed, images that could be
of a moth or could be of a moldy head of broccoli.


--
Tony Cooper - Orlando, Florida