Re: Canon 30D
- From: JPS@xxxxxxx
- Date: Thu, 23 Feb 2006 23:04:01 GMT
In message <5qqLf.14710$yK1.1851@xxxxxxxxxxxxxxxxxxxxxxxxxx>,
"Douglas" <aliens@xxxxxxxxx> wrote:
<JPS@xxxxxxx> wrote in message
news:a2kpv1tafpj989s5dh77u44r5v96goo3qj@xxxxxxxxxx
: In message <mianv1h64vq69hj09meu555tpot4navph4@xxxxxxx>,
: John A. Stovall <johnastovall@xxxxxxxxxxxxx> wrote:
:
: >And two pretty much pointless lenses. The product improved 85L is ok
: >but why another EF-S with IS?
:
: The new lens is 17-55IS, to it stands the chance of being much sharper
: and less distorted than the 17-85IS. It is also f/2.8, enabling
: shooting handheld in yet lower light. 1/3s at f/2.8 at ISO 1600 sounds
: intriguing to me.
: --
:
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: John P Sheehy <JPS@xxxxxxx>
: ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
Where ever you got the notion you could shoot much at f/2.8 and have any
usable depth of field could not possibly have been from the real world.
DOF is a function of magnification, at a given f-stop (and recording
medium or display resolution, if you take those into account). With a
17mm lens, only things that are very close to the lens will have that
paper-thin DOF.
Focusing on a nose at f/2.8 will produce an out of focus nose and blurred
ears. The situation only gets worse from there on. The only value f/2.8 has
is in providing brighter previews.
I would agree with 1.2 and 1.4 lenses in general, because their optics
are usually poor wide open, but many f/2.8 lenses are good, wide-open.
For DOF, again, magnification is a major issue, not f-stop alone.
Just the suggestion you can shoot ANY SLR camera at 1/3rd of a second
without the mirror being locked up is pretty intriguing to me too. It can't
be done and won't ever be possible as long as the mirror has to swing away
and back. Even with the mirror up, the vibrations from the shutter itself
will have an effect.
Hand-holdability, all other things being equal, is determined by
magnification, just like DOF. That's why you can't hand-hold your 100mm
macro at 1:1 at 1/100, but you can at infinity. The "1/fl" or
"0.625/fl" (for 1.6x crop sensors) rule of thumb is because of
magnification at a distance; not because of focal length per se.
Or do you use a leaf shutter in a special lens adaptor
in your dream of nirvana?
No, I use my mouse-trap-sounding 20D, which is more noise than anything,
and get shots at 28mm with IS that are reasonably sharp at 1/5, and
expect the same for about 1/3 with 17mm and IS. With my "Pod" beanbag,
I can go even further. I only carry around full-sized tripods on rare
occasion; I find them very restricting most of the time.
Another technique I use for long exposures is to hang the camera from my
neck, and have two legs from a mini-tripod resting on my chest. I have
taken normally-sharp images at night in Manhattan at 1/2 with my 10-22mm
Canon, stopped down to f/4.5. The IS will tighten this up as well.
--
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John P Sheehy <JPS@xxxxxxx>
<<> <>>< <>>< ><<> <>>< ><<> ><<> <>><.
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