Are IS lenses doomed ?

In article , Bill Funk
writes
On Sun, 21 Jan 2007 02:17:17 -0800, Bryan Olson
wrote:

Skip wrote:
"Bryan Olson" wrote:
Prometheus wrote:
Why not quote the angle of view that the lens gives with the sensor? Most
users are not interested in the focal length per se. I realise that macro
work and photometry can require more than the angle of view.

Yes, that seems like a good idea. Call an angle an angle and a
focal length a focal length.

Stating everything relative to 35mm full-frame is silly, especially
if it's not even what most people use.

Well, with so many sensor sizes, and proportions, on the market, 35mm
probably seems like the best to pick for a standard, since most of the
digital cameras, both point and shoot and DSLR, are similar in size, or at
least started out that way, to 35mm film cameras. And, originally, most of
the customers who migrated to digital came there from 35mm film. What
standard would you propose?

The proposal I like is to specify angle-of-view directly, without
reference to a standard sensor size.

Ane which angle of view would you print on, say, a Canon 17-40mm lens?
Or a Nikon 50mm lens?

Which is the same problem as using the pretend focal length; there is no
substitute for understanding through experience.

--
Ian G8ILZ
There are always two people in every pictu the photographer and the viewer.
~Ansel Adams

On 21 Jan 2007 07:24:30 -0800, wrote:


dennis@home wrote:
"Neil Harrington" wrote in message
...

DoF is different, of course. But I think that's secondary for most users
most of the time, in choosing a focal length. The *difference* in DoF for
dSLRs I think is relatively small, especially since the greater
magnification for the final print cancels some of the difference out.

Different?
If you put a 50mm lens on a camera the DOF will be the same whatever
film/sensor is fitted.

No, the DOF will be smaller for a smaller sensor/film format, all else
equal. This is because DOF is defined on a print, and to obtain the
same sized print from two sensors of different sizes, the image from
the smaller one must be enlarged more, thus enlarging the circle of
confusion more. In other words, a smaller sensor needs a smaller circle
of confusion, so the DOF is smaller, if all else (focal length,
aperture etc) is equal.

I agree with this. DOF is smaller in the smaller sensor camera when
the aperture, focal length, and subject-sensor distance are the same.

However, all is not equal. The images captured differ because the
angles of view differ.

If the two cameras are set up for the same angle of view, then the
smaller sensor camera has more DOF at the same aperture. The DOF will
be about the same when the smaller sensor camera lens is opened one
stop.

KS

In article , David
Dyer-Bennet writes
Rebecca Ore wrote:
In article ,
Prometheus wrote:

Cameras are about making photographs, they are not a theoretical
math-lab experiment.
applause

Understanding the physics in detail is necessary for some kinds of
work, and helpful for others (or at least for some *people*; depending
on how your head works). And not for still others.

An understanding, even if only of the limitations, is important. Even
where understanding is necessary a photograph will be taken.

Theoretical work should, as always, be verified by experiment.

It could make cosmology interesting.

--
Ian G8ILZ
There are always two people in every pictu the photographer and the viewer.
~Ansel Adams

"Bryan Olson" wrote in message
et...
Bill Funk wrote:
[ . . . ]

The problem is that most serious photographers are familiar with lens
coverage in terms of focal length as it pertains to 35mm photography
now.

That's a point. In the U.S. we couldn't even go metric.

We could and we *have*, where there's any reason to do so. We've described
the focal length of camera lenses in millimeters since before I bought my
first 35mm camera (American made, BTW) in 1951. Metric is useful for that,
much more useful than inches. It's also very useful in many ways in
medicine -- describing not only dosages but many kinds of other
measurements, so as anyone who's worked in a hospital knows almost
everything in them is metric.

Scales for body weight and height are the exception, and that's fine.
Pounds, feet and inches work just as well for those things as any other
units and there's no reason to change. Similarly, there's no reason to
change from using miles for highway distance, or ounces for mail, or quarts
and half gallons for containers of milk. Those are all useful units for
those purposes.

People who think we should change *everything* to metric are just too
doctrinaire about the subject. There were good reasons in Europe to change
from miles to kilometers, but those reasons don't obtain here.

Neil

dennis@home wrote:

Your definition of DOF depends on viewing distance from the print.
Think about it. 8-)

Hi. I have. It's not my definition, it's the one used for the markings
on your lenses and for DOF calculators. It is the one used in books etc.

On Sun, 21 Jan 2007 12:22:50 -0500, "Neil Harrington"
wrote:


"Bryan Olson" wrote in message
. net...
Bill Funk wrote:
[ . . . ]

The problem is that most serious photographers are familiar with lens
coverage in terms of focal length as it pertains to 35mm photography
now.

That's a point. In the U.S. we couldn't even go metric.

We could and we *have*, where there's any reason to do so. We've described
the focal length of camera lenses in millimeters since before I bought my
first 35mm camera (American made, BTW) in 1951. Metric is useful for that,
much more useful than inches. It's also very useful in many ways in
medicine -- describing not only dosages but many kinds of other
measurements, so as anyone who's worked in a hospital knows almost
everything in them is metric.

Scales for body weight and height are the exception, and that's fine.
Pounds, feet and inches work just as well for those things as any other
units and there's no reason to change. Similarly, there's no reason to
change from using miles for highway distance, or ounces for mail, or quarts
and half gallons for containers of milk. Those are all useful units for
those purposes.

People who think we should change *everything* to metric are just too
doctrinaire about the subject. There were good reasons in Europe to change
from miles to kilometers, but those reasons don't obtain here.

It helps a heck of a lot if we all use the same units. Ever been to a
conference where some are using deg C and others deg F? How about
situations where you are talking to a customer about pressure and have
dutifully converted psi to kilopascal, only to discover that they only
understand kg/sq cm? It is confusing and unnecessary.

But would the U.S. officially convert to a system of units invented by
outsiders? By the French, even?

There is also the fact that many in the U.S. are moronically
conservative (by which I mean they don't understand things that are
different). In southern Arizona, the highway to Mexico is sign-posted
in metric as well as U.S. measure. Well, sort of. They converted miles
to km, but in the end were not brave enough to convert mph to kph,
because many Americans would take it as license to go 100 mph just
because of the 100 in 100 km/h.

KS

Prometheus wrote:
In article , David
Dyer-Bennet writes
Theoretical work should, as always, be verified by experiment.

It could make cosmology interesting.


"Cosmologists are often wrong, but never in doubt" (Landau).

Prometheus wrote:
In article , David
Dyer-Bennet writes
Rebecca Ore wrote:
In article ,
Prometheus wrote:

Cameras are about making photographs, they are not a theoretical
math-lab experiment.
applause

Understanding the physics in detail is necessary for some kinds of
work, and helpful for others (or at least for some *people*; depending
on how your head works). And not for still others.

An understanding, even if only of the limitations, is important. Even
where understanding is necessary a photograph will be taken.

Some people have an intellectual need to understand the physics. Others
just want to know enough of the engineering rules to take their photos.
And the rest grouse about how their photo "didn't come out" :-).


Theoretical work should, as always, be verified by experiment.

It could make cosmology interesting.

Yes, it does; they can't perform most of the interesting experiments, so
they have to work more indirectly. And leaves their results less
certain than if directly verified, in the meantime.

In article ,
David Dyer-Bennet wrote:

Understanding the physics in detail is necessary for some kinds of work,
and helpful for others (or at least for some *people*; depending on how
your head works). And not for still others.

Understanding diffraction is important since it's why stopping down to
f/32 and enlarging to two feet by three feet only works on large format
films/sensors unless you're trying to soften focus.

What sort of photography requires knowing physics in detail?
(Astrophysical photography comes to mind, but even working out lighting
problems can be done by looking as well as knowing angles of reflection).

Most people aren't getting why DOF is measured on prints and why COC are
relative to what you're going to do with the raw image/negative/slide.

If you're shooting f/64 on 8x10 film or larger, you will have an
enormous depth of field and diffraction would not have done as much
visible damage to the final print as it would have if you'd shot f/32 on
a D-50 sized sensor.

And what's acceptable COC for you might be something I found
unacceptably soft. Personal taste will always play a part in this.

Over in photo.net, many people post photos. While people can't post
photos here, they can post links to their work. We're discussing
cameras in the abstract.

King Sardon wrote:


But would the U.S. officially convert to a system of units invented by
outsiders? By the French, even?


The metric system has been a legal system of trade units in the US since
1866. (However, all metric legislation in the US has always allowed for
imperial measure as well).

The US signed the "Metre convention" in 1878 as one of the original 17
countries party to the convention, the year after the first countries
signed on to it and is prominent in participating in the various
conventions relating to maintenance of the system and improving its
references.

The US military, in particular the Army and Marine Corps are highly metric.

More and more goods are available in the US in metric. Esp. bottled goods.

Most US government labs operate in metric.

The CIA "factbook" is in metric, including stats about the US. (Some
exceptions, such as maritime claims which are stated in nautical miles)
https://www.cia.gov/cia/publications...k/geos/us.html

The US will, in time, be completely metric. You (Americans) should do
as Canada began in the 1970's, transition over beginning with easy
things like speed limits and distances; then "grocery" items, and so on.

Canada is almost completely metric, but certain things such as building
materials will be hard to switch over (due to building codes and so on).

There's a good article on the metric system and the US on Wiki.

Cheers,
Alan

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