Are IS lenses doomed ?

"Neil Harrington" wrote in message
. ..

Exactly. And I think that even long after 35mm is dead and gone, its use
as a familiar standard for focal lengths will probably go on and on. It's
already *the* standard of comparison for focal length conversions, and
once such a standard is established there's no obvious reason to change
it.

You can't just convert the focal length and come up with the correct answer.
Not every lens characteristic changes when you change sensor size.
Things like the DOF stay the same.
They only change if you move the camera or zoom to reflect the change in
field of view.

In article , King Sardon
writes
On Sat, 20 Jan 2007 16:32:53 +0000, Prometheus
wrote:


I have sometimes estimating the angel of the scene and then converted
that to length via the normal lens in order to decide which lens to use.
The basic process being "do I want half, quarter or eighth of the (55mm)
normal lens", and thence select the 105mm, 200mm or 400mm lens. I do not
think of the fractions of a degree other than implied by simple
fractions (i.e. 50, 25, 12 1/2, 6 1/4). Do you think to yourself "do I
need 440 or 450 mm here?"

Most of the time I'm sure people guess at the focal length needed...

Probably by remembering that the 100mm covers half the width of the 50mm
lens, and not by remembering that its centre has to be twice as far from
the film. Of course there are lost of lengths and so familiarity with
the lenses used will play a significant part in choice of lens ahead to
be used.

and anyway, often more than one will work because you might want
different framing of a particular subject or scene.

Indeed, the wide will capture the cathedral, but only a very-narrow will
capture the carving on the roof (assuming they can focus on the
subject).

But sometimes it is necessary to know the focal length, for instance
when calculating depth of field for a critical subject,

For which you require the true length, and the value of CoC that is
acceptable to you for that photograph.

or when
determining beforehand the lens you will need for important shots.

Always, but you will need to consider more than the focal length (or
coverage at the subject)

Examples include figuring out what lens to buy for a particular kind
of macro photography,

Focal range and magnification along with clear working distance are the
important factors. Of course these are related to focal length, but you
will work them out first and then chose a lens to provide the
performance, whether it is marked as 100mm, 25 degrees or 'red with blue
dots'.




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

On Sat, 20 Jan 2007 05:41:46 GMT, 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.

Yeah, that'll work.
Given a tree line at starts 217' away, with the trees an average of
13' apart, how many trees does it take to make up a 57° angle of view?

The problem is that most serious photographers are familiar with lens
coverage in terms of focal length as it pertains to 35mm photography
now. Changing that won't help anyone at all. Those who aren't familiar
with lens coverage that way will need to learn *some* way if they want
to become serious. There's nothing wrong with using a system that's
already in use and understood.
To change an established system, there needs to be an over-riding
reason. The idea that lenses should be re-marked to reflect the size
of the sensor used will only confuse everyone, especially those who
want to deal with cameras that use different sized sensors.
A standard that uses 24x36mm 35mm frame size as a standard, with
conversion factors for different sized sensors, works well, and has
the advantage of *already* working well.

--
Angelina Jolie moved into
a mansion in New Orleans
with Brad Pitt where they
say they will be very
involved locally. The
actress is nothing if not
meticulous. Whenever Angelina
Jolie orders in Chinese she's
very careful to specify boy or girl.

"Alan Browne" wrote in message
...
VC wrote:
The release of Sony Alpha with the image stabilization in camera (
although this is not new) highlighted the fundamental problem with Canon.
Canon have had IS lenses long ago as it would be very difficult to do
in-camera stabilization in film cameras. The digital cameras had to
support older lenses including the ones with IS. If Canon developed a
camera with in-body stabilization it would hurt Canon sales and
reputation.
So I guess Canon will continue with its nonstabilized bodies and when
Sony or someone else will achieve the same image sensor quality Canon
will find itself in a very difficult situation.
There is a very small advantage in having IS in the lens but it is not
significant enough to grant double and triple cost of the same quality
lenses.

For specific shooting, yes there is an advantage to "in lens"
stabilization... about a stop to 2 stops worth over the "in camera".

What testing proved this, the only testing I have seen is in a German mag
where they showed there was little difference between the two systems?

The advantages of the in-camera are a margin (2 stops, sometimes more) and
all your lenses benefit.

And no, in camera will never achieve what "in lens" stab can do.

What testing proved this, the only testing I have seen is in a German mag
where they showed there was little difference between the two systems?

And no, neither system is doomed.

And of course, for those who continue to shoot film as well as digital,
IS/VR will provide stab that simply is not available in film cameras.

Cheers,
Alan

In article , Bill Funk
writes
On Sat, 20 Jan 2007 05:41:46 GMT, 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.

Yeah, that'll work.
Given a tree line at starts 217' away, with the trees an average of
13' apart, how many trees does it take to make up a 57° angle of view?

That is simple trigonometry, not that in practice you would work it out
unless you needed to provide measurements for evidence or some such. A
more difficult question would be 'Given a tree line at starts 217' away,
with the trees an average of 13' apart, how many trees does it take to
fill a 50mm lens on a 35mm FF camera?'

The problem is that most serious photographers are familiar with lens
coverage in terms of focal length as it pertains to 35mm photography
now. Changing that won't help anyone at all. Those who aren't familiar
with lens coverage that way will need to learn *some* way if they want
to become serious. There's nothing wrong with using a system that's
already in use and understood.

To change an established system, there needs to be an over-riding
reason. The idea that lenses should be re-marked to reflect the size
of the sensor used will only confuse everyone, especially those who
want to deal with cameras that use different sized sensors.

A very good reason for not marking lenses with "corrected focal length".

A standard that uses 24x36mm 35mm frame size as a standard, with
conversion factors for different sized sensors, works well, and has
the advantage of *already* working well.

Perfectly true; I was not entirely serious in suggesting pulling the
familiar away from under peoples feet and expecting them to accept
angles as "the new black".

But, if I use my MF camera should I say it has a 50mm (x0.66) lens? I
know that 75mm on the MF and 50mm on the 35mm give about the same view,
if I look at a scene and it is about a quarter of normal (which I can
estimate) I know I need a lens of about a quarter the angle which is
four times the length. If I imagine the MF lens to be "50mm" this could
mislead me in to fitting a real 200mm lens when it should be 300mm.

What of macro lenses? If I transfer a 100mm macro lens from my 35mm (FF)
camera to my DSLR (APS) it does not become a 160mm macro lens, the
distances of focal plain to lens and lens to subject remain those of a
100mm lens.

The 'correction factor' is useful when explaining to someone else
provided we remember to qualify it as being "equivalent to" or "like"
and do not forget that we are equating only one aspect of the lens's
performance.



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

On Sat, 20 Jan 2007 20:47:27 +0000, Prometheus
wrote:

In article , Bill Funk
writes

Yeah, that'll work.
Given a tree line at starts 217' away, with the trees an average of
13' apart, how many trees does it take to make up a 57° angle of view?

That is simple trigonometry, not that in practice you would work it out
unless you needed to provide measurements for evidence or some such. A
more difficult question would be 'Given a tree line at starts 217' away,
with the trees an average of 13' apart, how many trees does it take to
fill a 50mm lens on a 35mm FF camera?'

Twelve. It's not hard. Just use similar triangles, A/B = A'/B'. In
this case the width of the field at the subject is 36/50*217 = 156
feet.

KS

In article , King Sardon
writes
On Sat, 20 Jan 2007 20:47:27 +0000, Prometheus
wrote:

In article , Bill Funk
writes

Yeah, that'll work.
Given a tree line at starts 217' away, with the trees an average of
13' apart, how many trees does it take to make up a 57° angle of view?

That is simple trigonometry, not that in practice you would work it out
unless you needed to provide measurements for evidence or some such. A
more difficult question would be 'Given a tree line at starts 217' away,
with the trees an average of 13' apart, how many trees does it take to
fill a 50mm lens on a 35mm FF camera?'

Twelve. It's not hard. Just use similar triangles, A/B = A'/B'. In
this case the width of the field at the subject is 36/50*217 = 156
feet.

Congruent triangles is not an issue, more important is that we are still
considering angels of view and not focal length.

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

On Sat, 20 Jan 2007 20:47:27 +0000, Prometheus
wrote:

But, if I use my MF camera should I say it has a 50mm (x0.66) lens? I
know that 75mm on the MF and 50mm on the 35mm give about the same view,
if I look at a scene and it is about a quarter of normal (which I can
estimate) I know I need a lens of about a quarter the angle which is
four times the length. If I imagine the MF lens to be "50mm" this could
mislead me in to fitting a real 200mm lens when it should be 300mm.

Obviously, we aren't talking about MF.

What of macro lenses? If I transfer a 100mm macro lens from my 35mm (FF)
camera to my DSLR (APS) it does not become a 160mm macro lens, the
distances of focal plain to lens and lens to subject remain those of a
100mm lens.

The 'correction factor' is useful when explaining to someone else
provided we remember to qualify it as being "equivalent to" or "like"
and do not forget that we are equating only one aspect of the lens's
performance.



--
Angelina Jolie moved into
a mansion in New Orleans
with Brad Pitt where they
say they will be very
involved locally. The
actress is nothing if not
meticulous. Whenever Angelina
Jolie orders in Chinese she's
very careful to specify boy or girl.

"dennis@home" wrote in message
...

"Neil Harrington" wrote in message
. ..

Exactly. And I think that even long after 35mm is dead and gone, its use
as a familiar standard for focal lengths will probably go on and on. It's
already *the* standard of comparison for focal length conversions, and
once such a standard is established there's no obvious reason to change
it.

You can't just convert the focal length and come up with the correct
answer.
Not every lens characteristic changes when you change sensor size.
Things like the DOF stay the same.
They only change if you move the camera or zoom to reflect the change in
field of view.

Actually, I believe DOF is different, but, otherwise, everything else, like
perspective, stays the same.

--
Skip Middleton
www.shadowcatcherimagery.com
www.pbase.com/skipm

"Prometheus" wrote in message
...
In article , Neil Harrington
writes

"Prometheus" wrote in message
...
In article , Neil
Harrington
writes

"Prometheus" wrote in message
.. .
In article , David Littlewood
writes

------- Cut, on sensor and lens multiplier or divider ---------

Personally don't see why a term is required. It's an image size ratio,
everything else works as before; why not call it image size ratio?
Better,
since the "ratio" is to a film format which will become increasingly
irrelevant to new generations of photographers, eventually it will be
enough to just quote size, as I said

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.

And long lenses require more too. You're quite right, angle of view is
the
important thing -- but only with normal to wide-angle lenses. Users
could
in
time get used to the idea that "28mm equivalent" meant "75 degrees
corner
to
corner" and end up just calling such a lens a 75-degree lens. There is a
small fly in that ointment, in that third-party lenses made in more than
one
mount would be slightly different on a Nikon than on a Canon, 1.5x and
1.6x
focal length multipliers respectively and the necessary adjustments to
angle, but those adjustments in most cases would be small.

With long lenses however it's the magnification that the user is
interested
in, not the angle of view. Sure, one is necessarily related to the
other,
but for example calling a 200-400mm zoom a
12-degree-20-minute-to-6-degree-10-minute lens gets a little unwieldy,
isn't
very informative for most users -- and is only correct for the 24x36
format
anyway.

Magnification depends on the focal distance as well as the focal length,

Sure, but "near infinity" is generally understood when comparing focal
lengths for purposes of magnification.

Only in a crudely qualitative sense; thing "near infinity" are arbitrarily
small, magnifying them only serves to make them arbitrarily larger.

it is independent of the "multiplier factor". For macro you are
interested
in the angle of view and the focal distance, which is why I said that "I
realise that macro work and photometry can require more than the angle
of
view".

So I think using an appropriate multiplier to relate sensor focal
lengths
to
some familiar standard continues to be useful, and while there's nothing
cosmically significant about the 35mm format at least it is a familiar
standard, and by far the most familiar one.

It is a convenience that most people will understand, I made my
suggestion
half in jest, with far more variation in sensor size than there was in
film size it becomes important to know that there is more than focal
length to consider,

As long as the lens factor used is correct, it takes care of the
differences
in sensor size for the purposes most users are interested in, i.e.
magnification or angle of view.

I wonder how many users of compact cameras know or care what the focal
length is, using the view finder to obtain the view required is the
principle interest. The users of DSLRs will make a purchases based on
their requirement taking account of the 'lens correction factor', and then
frame with the viewfinder having little regard for the focal length.

although most of the cameras have fixed lens without any focal length
marks it is probably not a great problem.

Just so, but users still want to know what the focal length range is in
terms of some familiar standard. There's no reason of cosmic importance
for
24 x 36 to be that standard, other than the fact that it is by far the
most
familiar one.

Indeed, as a comparison for relative angle of view it is most useful, and
I do use it, but what of DoF?
--
Ian G8ILZ
There are always two people in every pictu the photographer and the
viewer.
~Ansel Adams