Are IS lenses doomed ?

Lionel wrote:

[0] You'll see 'macro' specifications on most of its non-macro lenses
as well, but those lenses typically achieve a magnification of no more
than 0.25x, & you can only get that at a very narrow range of
focus/zoom settings & subject distances.

Yes. The term is used very very loosely in most photographic
conversation, and even in actual markings on real equipment. So my
default understanding is that it means "closeup" today, despite knowing
the technical definition (for 30 years or so; forget exactly when I
first learned that bit).

But, that's certainly the official definition, and I'm not complaining
about its use. It's a distinction worth preserving, I think; I'm
generally in favor of precise vocabulary and preserving distinctions. I
just don't expect to use it precisely myself without having to explain
every time, these days.

Tony Polson wrote:
On Wed, 31 Jan 2007 03:19:53 GMT, Rebecca Ore
wrote:

The thing about 35 mm and smaller is that those cameras are easy to
carry. But with plastic and titanium, a medium format camera could be
lighter than the old metal bricks.



That was the principle behind the Bronica ETRSi, and to a lesser
extent the SQAi. Both used modern materials (although not titanium)
to produce a camera that weighed much less than a comparable
Hasselblad.

Having said that, most of the weight of a medium format SLR is in the
lenses, and the pentaprism - if one is used. Personally, I decided it
was better to become adept in the use of a waist-level finder with my
medium format gear, as the weight saved made weddings a much less
tiring proposition.

Now I just shoot digital, with the Canon EOS 5D.



The Hasselblad body and mag are worth studying closer - the magazine
uses a solid magnesium (not mag alloy) central casting. I believe the
500 body post C/M uses magnesium as well. Most of the weight difference
has always seemed to me to be in the lenses.

David

Lionel wrote:
On Mon, 29 Jan 2007 12:28:30 GMT, Rebecca Ore
wrote:

No, I was saying that a digital camera can't produce as good a 16x20 as
a 4x5 camera.

That's only correct if both photographers are equally skilled, & are
using equally good lenses & cameras, which is rarely the case.

That's silly. For 4x5 the camera seldom matters at all. The lens matters,
but excellent 4x5 lenses were made in the 90's. That's the **18** 90s.
Skill does matter a bit, but the inherent factor of 3 to 6 can't
easily be beat. I've made better SNAPSHOTS with a rangefinder
4x5 than with the greatest of care with a 35 mm SLR.

Doug McDonald

"Lionel" wrote in message
...
On Wed, 31 Jan 2007 17:00:08 +0100, acl
wrote:

Lionel wrote:

Absolutely. The problem is whether the VR system is *capable* of
tracking the shake *accurately enough* at those magnifications for it
to be effective.

Ah, so your point is that at these magnifications, a given movement of
the moveable lens element will produce a much larger motion in the image
than at lesser magnifications, and that the system tolerances are too
large?

Yes, that's exactly my point. I haven't done a terribly good job of
describing it, because it's difficult for me to do so without dropping
into electrical-engineering jargon, & any other EEs reading this would
likely have reached the same conclusions, & wouldn't need any
explanations.

That's interesting, maybe you're right. In fact, you're probably
right, now that I think of it. Certainly, at large enough
magnifications, you're basically using the lens backwards, so it's like
using a lens normally (ie to focus at a distant object) and projecting
the image from the sensor to the object. So huge movements of the
projected image by small movements of the stabilising element. Makes
sense. The question is at which magnification the crossover from
usefulness to uselessness occurs, and this depends on the tolerances.

Exactly. There are a number of factors involved, mostly involving the
time constants of the feedback network in the servo=sensor control
loop, (which need to be different for different FLs, & different
motion ranges), the positional accuracy of the physical servo mech,
the sensitivity of the sensor (presumably a silicon accelerometer), &
a couple of other things that might be significant.

All very interesting, if somewhat incomprehensible to me since I don't
really know how the stabilizing element or group works. I can understand the
motion-sensing and correcting mechanism all right (not at an engineering
level, but I think enough to get the principle) but it's how the element(s)
movement counters the motion at the image plane that I don't understand.

Presumably that component must move laterally, which moves the image
laterally. But is it possible to have a decentering of any elements without
some degradation to the image, even when they're designed expressly to be
moved in this way? It seems to me that there must be some optimal position
for the element, rather than an infinite number of equally good positions
over a certain range. I have assumed that that's at least one reason that
manufacturers of stabilized lenses advise turning the stabilization off
under some conditions, e.g. when on a tripod. Of course that's nothing to do
with macro work, particularly.

But what you fellows are saying is that it's failure of the
motion-compensating system to do its work accurately at magnifications
approaching 1:1, because accuracy demands become too high for unavoidable
tolerances in the system, correct?

I don't understand the "basically using the lens backwards" part. If you
were talking about magnifications *higher* than 1:1, I could understand
that.

Neil

"Rebecca Ore" wrote in message
...
In article ,
David Dyer-Bennet wrote:

Since I *haven't* ever handled the 105mm VR Micro myself, I certainly
don't have any opinion of my own on the utility of its VR for macro
photography.

VR helps up to at least 1-1/2 feet, as I've demonstrated, just not as
much as it helps at longer distances.

If that 1 1/2 feet is from subject to film plane, as focusing distances are
traditionally measured, with a 105mm lens that must be pretty close to
1:1 -- unless of course the focal length shortens a great deal as it focuses
closer.

Most macro lenses nowadays do shorten f.l. as they focus closer -- at least,
mine do, and I understand others do as well.

Neil

"Lionel" wrote in message
...
On Wed, 31 Jan 2007 08:35:24 -0500, "Neil Harrington"
wrote:


"Bryan Olson" wrote in message
y.net...
Neil Harrington wrote:
Who uses that so-called "crop factor" to do anything ELSE but to
multiply
the focal length with? Who uses it in connection with actual cropping,
in
any way, shape, manner or form?

Of course we don't use it for cropping -- the camera already did
that for us.

Then what do you use the 1.5x factor FOR?

To tell us how much the smaller sensor is *going to crop* our image
down from what we'd get on a full-frame sensor. Duh.

And why this is important for you to know? To what use do you put this
alleged how-much-the-smaller-sensor-is-going-to-crop-our-image information
(which by the way would be about 1/3 linearly, not 1.5)?



I have asked this several times. None of you "crop factorists" have even
attempted an answer. The reason for this I think is obvious: you use it to
multiply the focal length with,

In real world photography, it amounts to the same thing.

Hardly. You can multiply the focal length by 1.5 times; you cannot crop
anything 1.5 times.



but dare not say so because that would make
you an apostate in the Holy Church of Pretending This Factor Has Something
to Do With Cropping.

Using it as a multiplier is, in short, the elephant in the room you cannot
notice -- and your fond hope is that no one else notices.

Oh for ****'s sake. Either mental model (crop factor or focal length
multiplier) is perfectly usable for most photographic purposes. No,
neither is perfect, but they're both useful rules of thumb.

"Focal length multiplier" is exactly what you do with it. You don't -- and
can't -- crop anything by a factor of 1.5x.


You just
use the one that makes most sense to you, personally, & don't worry
about the whole issue. Most people simply don't care, & just leave
these sorts of nit-picking arguments to trolls like Rebecca who think
they know a lot more about optics than they actually do.

Does the expectation of proper terminology deeply offend you for some
reason?

Neil

"Tony Polson" wrote in message
...
On Wed, 31 Jan 2007 09:08:25 -0500, "Neil Harrington"
wrote:

But a good argument is something else entirely. As Sean O'Faolain noted,
"Irish people have a love of aimless disputation" -- and among the Irish
it's regarded as poor form ever to conclude an argument, since that
deprives
everyone of the pleasure of the thing. The only problem here is that some
arguments just go around and around without getting anywhere.


But if you have Irish blood, why would that be a problem?

I do, and it's not so much that it's a problem as that it degrades the
quality of the argument after a while. While it's true that any argument is
better than no argument at all, one should always strive for quality.



Some things in life can never be fully resolved. But if you learn to
accept that, you have actuallly gotten somewhere.

I don't see how.

Neil

In article ,
David Kilpatrick wrote:

The Hasselblad body and mag are worth studying closer - the magazine
uses a solid magnesium (not mag alloy) central casting. I believe the
500 body post C/M uses magnesium as well. Most of the weight difference
has always seemed to me to be in the lenses.

I hefted a Hasselblad when I was living in Virginia. I have been
tempted since the prices are low now (relatively -- the Mamiya RB 67s
are even lower). They're still big cameras. The twin-lens reflexes
tend to be better balanced on a neck strap, but are either insanely
expensive for fixed lens(es) cameras or are rather older. If a medium
format was going to live on a tripod, the RB 67 is also pretty tempting.
If the Hassy can be reasonably hand-held, um, with a digital back.

And if I had that kind of money.

In article ,
"Neil Harrington" wrote:

If that 1 1/2 feet is from subject to film plane, as focusing distances are
traditionally measured, with a 105mm lens that must be pretty close to
1:1 -- unless of course the focal length shortens a great deal as it focuses
closer.

Judging by the readings on the lens, it was between a third and a
quarter life size on the sensor. The maximum close focus for the lens
is 0.314 meters, a little over 12 inches.

Most macro lenses nowadays do shorten f.l. as they focus closer -- at least,
mine do, and I understand others do as well.

Shaw has something about that, if I remember correctly. The virtual
aperture changes, too.

A focusing rail would be nice -- and a flash off camera. I made a copy
of Rita's post about her macro lighting set-up.

On Wed, 31 Jan 2007 16:36:49 -0500, "Neil Harrington"
wrote:
"Tony Polson" wrote in message
.. .

Some things in life can never be fully resolved. But if you learn to
accept that, you have actuallly gotten somewhere.

I don't see how.

I didn't expect that you would! Perhaps this will help*:

Not everything in life has a deterministic explanation. Not every
question has a straightforward answer. When you realise that, you can
stop wasting your time looking for one.

Don't try to equate facts with knowldge, nor knowledge with
understanding, nor understanding with wisdom.

(* or maybe not!)