50mm pictures with D300

"John Navas" wrote in message
...
On Tue, 22 Jan 2008 12:22:48 -0800 (PST), JimKramer
wrote in
:

On Jan 22, 3:02 pm, "Rita Berkowitz" wrote:
JimKramer wrote:
Have you used or heard the term "hot water heater"? Why would you
need to heat water that is already hot? And yet 98% of water heater
users refer to the water heater as a "hot water heater."

Wrong! Depending on the application it can be called a booster heater
or
tempering tank. Some commercial applications need to boost standard
120º-140º hot water to 180º for safety and sanitary reasons. Nothing
beats
a kick-ass 480V three-phase booster heater!

Rita

Got one of those in your house? Delta or Y configuration for the
elements? What other 3-phase devices do you have installed at home?
What are you washing that needs to be sanitized so? :-) Hmm... Got a
picture? :-) No, never mind. :-)

Typically, I've seen a tempering valve used with a commercial water
heater to supply domestic hot water if a stand alone domestic water
heater was not warranted, i.e. a restaurant setting, but not a school
with a cafeteria.

I suspect you should look up what a tempering tank really is and then
I will let you use the term "tepid water heater" when referring to the
water heater when installed in such situations.

I always find it interesting to see what people actual do and don't
know. :-)

Especially in the case of Rita.

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)
At least, John, Rita isn't running around telling people to get their hot
water heaters fixed.

Wink,
Dudley

"Dudley Hanks" wrote in message
news:rdwlj.13670$vp3.2574@edtnps90...

"John Navas" wrote in message
...
On Tue, 22 Jan 2008 18:03:52 -0500, "Rita Berkowitz"
wrote in :

Sosumi wrote:

I've seen people take amazing good pictures with a simple camera,
without any other than standard lenses. How else would they zoom
other then with their feet?
Portrait or landscape orientation is also done by hand, not by lens.
Big part of the framing.

LOL! Amazing, isn't it? Some people just don't get it.

Indeed we don't. We use the correct focal length for the best possible
image based on such things as composition and perspective; i.e., we
don't spoil the image by using the wrong focal length.

"If all you have is a hammer, everything looks like a nail."

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

John, for such a good photographer, you seem to spend more time in front
of your computer than behind your eyepiece.

Why is that?

Curious,
Dudley

I'd be more curious as to why a seasoned photographer calls a veiwfinder an
eyepiece

In rec.photo.digital.slr-systems John Navas wrote:
On 23 Jan 2008 11:21:49 GMT, Chris Malcolm wrote
in :

That is exactly my point. The perspective of an image has to with the
relationships between all of the things in the entire image. That is
determined by three things, the position of the camera, where it's
pointing, and the subtended angle of view.

Perspective is simply the relationship of objects closer and farther
away; i.e., at different distances. It's why objects farther away look
smaller, and how much smaller is what perspective is all about. It is
not the overall image and/or the angle of view.

http://www.dpreview.com/learn/?/Glossary/Optical/Perspective_01.htm

If you photograph a subject with a tele lens and want it to have the
same size on the film or sensor when photographing it with a wide
angle lens, you would have to move closer to the subject. Because
this would cause the perspective to change, lenses with different
focal lengths are said to "have" a different perspective. Note
however that changing the focal length without changing the subject
distance will not change perspective, ...

Note that I said "position"
of the camera. That determines its spatial relationship to everything
in the image. "Distance to subject" doesn't work when the subject has
no clearly identifiable distance or is multiple.

There is always a subject.

But it doesn't always have a clearly identifiable distance. Consider
for example standing beneath a long cliff and photographing along its
length. The subject is the cliff receding into the distance. The
distance of the nearest part of the cliff at the edge of the image is
six feet. The distance of the furthest part is several miles.

What is the distance to the subject in this case?

Now walk forwards six feet. How has the distance to the subject changed?

Now change focal length from 24mm (35mm film equiv) to 100mm. The
distance to the nearest part of the cliff in the image has changed a
lot. The image also looks quite different. What is more you couldn't
walk forwards with the 24mm lens to get the same view of the cliff as
the 100mm lens did. Are you claiming that it is wrong to say that the
the perspective of the subject is different in these two images taken
from the same position with two different focal lengths?

I suspect you are, by your argument that a central crop of the 24mm
image will look the same as the 100mm image and therefore be the same
perspective. I agree that it would. So now let's now consider that
argument.

The three necessary and sufficient determinants of simple rectilinear
image perspective are position, direction of view, and subtended angle
of view.

These things have nothing to do with perspective.

The simple test is to photograph the same portrait with a wide angle
lens and with a telephoto lens at the same image magnification
(different subject distance), and note the difference in perspective
(e.g., enlarged nose in the wide angle shot). When photographed at the
same distance and cropped to match, the images and thus the perspective
are identical. Again, you simply cannot change perspective without
changing distance to subject, nohow, noway.

By centering your crop around the central axis of the viewing
direction that test has conveniently cropped off the parts where the
change in perspective is evident. If you crop to the left hand half of
the wider image, and then with twice the focal length swing round to
encompass the same view as the crop, you will get two different
looking images. What would you call those differences? I would call
them differences in perspective. And if there were any aids to judging
the perspective projection in the image, such as people and buildings
as in a street scene, then there would be something disinctly odd
looking about the perspective of the side cropped image. Yet the
photographer hasn't changed position. All distances remain the
same. All that has been changed is focal length and direction of view.

These differences are not as some have claimed distortion effects of
lenses because they're equally evident if you do the same thing with a
pinhole camera. And if you want to make two accurate perspective
sketches of the view using the theory of perspective projection as
elaborated by Renaissance painters with rulers, vanishing points,
etc., you would change the kind of perspective projection you were
doing to get the differences between the two images. Similarly if you
had a three dimensional model of the scene in a computer and wanted to
generate those two different images you would choose different
perspective projection parameters.

My definition of a difference in perspective between two images is
having to make a change in the perspective projection parameters to
generate the difference. And any change between two images generated
soley by a change of perspective projection I would call a change in
perspective.

That seems to me to be a logical definition, which could be made
formally mathematical in terms of the theory of perspective
projection, and which seems to be reasonably consistent with popular
uses of the term "perspective" as it applies to paintings and
photographs.

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

"Chris Malcolm" wrote in message
...
In rec.photo.digital.slr-systems John Navas
wrote:
On 23 Jan 2008 11:21:49 GMT, Chris Malcolm wrote
in :

That is exactly my point. The perspective of an image has to with the
relationships between all of the things in the entire image. That is
determined by three things, the position of the camera, where it's
pointing, and the subtended angle of view.

Perspective is simply the relationship of objects closer and farther
away; i.e., at different distances. It's why objects farther away look
smaller, and how much smaller is what perspective is all about. It is
not the overall image and/or the angle of view.

http://www.dpreview.com/learn/?/Glossary/Optical/Perspective_01.htm

If you photograph a subject with a tele lens and want it to have the
same size on the film or sensor when photographing it with a wide
angle lens, you would have to move closer to the subject. Because
this would cause the perspective to change, lenses with different
focal lengths are said to "have" a different perspective. Note
however that changing the focal length without changing the subject
distance will not change perspective, ...

Note that I said "position"
of the camera. That determines its spatial relationship to everything
in the image. "Distance to subject" doesn't work when the subject has
no clearly identifiable distance or is multiple.

There is always a subject.

But it doesn't always have a clearly identifiable distance. Consider
for example standing beneath a long cliff and photographing along its
length. The subject is the cliff receding into the distance. The
distance of the nearest part of the cliff at the edge of the image is
six feet. The distance of the furthest part is several miles.

What is the distance to the subject in this case?

Now walk forwards six feet. How has the distance to the subject changed?

Now change focal length from 24mm (35mm film equiv) to 100mm. The
distance to the nearest part of the cliff in the image has changed a
lot. The image also looks quite different. What is more you couldn't
walk forwards with the 24mm lens to get the same view of the cliff as
the 100mm lens did. Are you claiming that it is wrong to say that the
the perspective of the subject is different in these two images taken
from the same position with two different focal lengths?

I suspect you are, by your argument that a central crop of the 24mm
image will look the same as the 100mm image and therefore be the same
perspective. I agree that it would. So now let's now consider that
argument.

The three necessary and sufficient determinants of simple rectilinear
image perspective are position, direction of view, and subtended angle
of view.

These things have nothing to do with perspective.

The simple test is to photograph the same portrait with a wide angle
lens and with a telephoto lens at the same image magnification
(different subject distance), and note the difference in perspective
(e.g., enlarged nose in the wide angle shot). When photographed at the
same distance and cropped to match, the images and thus the perspective
are identical. Again, you simply cannot change perspective without
changing distance to subject, nohow, noway.

By centering your crop around the central axis of the viewing
direction that test has conveniently cropped off the parts where the
change in perspective is evident. If you crop to the left hand half of
the wider image, and then with twice the focal length swing round to
encompass the same view as the crop, you will get two different
looking images. What would you call those differences? I would call
them differences in perspective. And if there were any aids to judging
the perspective projection in the image, such as people and buildings
as in a street scene, then there would be something disinctly odd
looking about the perspective of the side cropped image. Yet the
photographer hasn't changed position. All distances remain the
same. All that has been changed is focal length and direction of view.

These differences are not as some have claimed distortion effects of
lenses because they're equally evident if you do the same thing with a
pinhole camera. And if you want to make two accurate perspective
sketches of the view using the theory of perspective projection as
elaborated by Renaissance painters with rulers, vanishing points,
etc., you would change the kind of perspective projection you were
doing to get the differences between the two images. Similarly if you
had a three dimensional model of the scene in a computer and wanted to
generate those two different images you would choose different
perspective projection parameters.

My definition of a difference in perspective between two images is
having to make a change in the perspective projection parameters to
generate the difference. And any change between two images generated
soley by a change of perspective projection I would call a change in
perspective.

That seems to me to be a logical definition, which could be made
formally mathematical in terms of the theory of perspective
projection, and which seems to be reasonably consistent with popular
uses of the term "perspective" as it applies to paintings and
photographs.

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

Exactly!

Impressed,
Dudley

"Dudley Hanks" wrote
news:7Trmj.28478$yQ1.16965@edtnps89...

............................................... ..

Exactly!

Impressed,
Dudley


Nothing like quoting a hundred lines of message across four newsgroups to
say "exactly"
Fer chrissakes..............

Now, to mess with your mind just a bit more, what would you say, John,
if
I told you I was taking part in a sociology experiment conducted by
the
Department of Justice, with the aim of trying to determine whether or
not
blind computer users are being discriminated against in their daily
net
activities, and that pending computer regulations could depend on what
you
have said already, and on how your react in the future?

More BS.

Whether it is or isn't, this type of study will happen, if it isn't
already.
And, you, my friend, will surely have some unwanted visiters.

More BS. And sad empty threats.

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

John, it is just too easy to mess with you.

I start by telling you that I'm just messing with your mind, and you come
back with "empty threats"?

How can messing with your mind be a threat? (Maybe you really believed me?)
AHAHAHA... AHAHAHA... AHA... HA... HA...
(That sounds sooo funny when heard through a screen reader!)

Laughing,
Dudley

gpaleo wrote:
"Dudley Hanks" wrote
news:7Trmj.28478$yQ1.16965@edtnps89...

.................................................

Exactly!

Impressed,
Dudley


Nothing like quoting a hundred lines of message across four
newsgroups to say "exactly"
Fer chrissakes..............

Agreed, but sometimes you need to be a little more forgiving.

David