I want a 400/500 f/5.6 IS/OS non-zoom lens . . .

"John McWilliams" <jpmcw.DeleteThis@comcast.net> a écrit dans le message de news:
TrGdnbEF2LRW4zranZ2dnUVZ_r3inZ2d.DeleteThis@comcast.com...
jean wrote:
> "Pudentame" <no.one.DeleteThis@no.were.invalid> a écrit dans le message de news:
> 47a5f286$0$30038$4c368faf@roadrunner.com...
>> Eric Miller wrote:

>> My photography doesn't earn enough I could justify buying it on credit,
>> but I can put a little away each payday ... and someday, I'll have enough
>> to buy it.
>>
>> In the meantime, I'll get by with the 300 I saved up and bought.
>
> Many people buy options for a car woth just as much as a 500mm lens
> without batting an eyelash yet those options get very little use, much
> less than a big lens would. The option in a car loses value, a good lens
> rarely so. Next time instead of getting a bigger engine or an on board
> computer or a huge sound system or leather seats, save the money for a
> nice lens.


Excellent points, Jean. Now imagine what you could buy with the savings
of not buying that next car!

I know, sometimes a car is a necessary evil, still managed to cycle almost
6000Km last year but I don't know if the sweat I poured out is less
polluting than a car exhaust for the same distance

Jean
 >> Stay informed about: I want a 400/500 f/5.6 IS/OS non-zoom lens . . . 

Ï "Fred McKenzie" <fmmck DeleteThis @aol.com> Ýãñáøå óôï ìÞíõìá
news:fmmck-1871B5.14105803022008@nntp.aioe.org...
> In article <Ahipj.38525$4w.20127@pd7urf2no>,
> Matt Ion <soundy106 DeleteThis @gmail.com> wrote:
>
> > Now look at your Maglite - the end of the barrel rotates to adjust the
> > reflector position to focus the beam. With the big 4-D model you can
> > light something a block away. This is partly due the fact that the
> > incandescent bulb produces light fairly evenly out all sides, rather
> > than just forward. Put an LED in its place, and you get almost no
> > "spillage" light to focus.
>
> Matt-
>
> You haven't gone shopping for a Maglite flashlight lately, have you? I
> have a 3-D Cell Maglite flashlight that came with a 3 Watt LED bulb.
>
Mine (2 AA) came with a classic incandescent lamp, and I have it in my tool
box, and run it with sanyo NImH.
> It came with a "spare" incandescent bulb stored in the end cap. When I
> tried it with the incandescent bulb, it was clearly not as bright as the
> LED bulb when focused to a spot. I didn't notice, but it may have had a
> better flood setting when intentionally de-focused.
>
> (They also sell genuine Maglite LED replacement bulbs to retrofit your
> old flashlight.)
>
> I think the real reason the LED isn't being seriously used for
> photography, is that it has to be focused to obtain the needed
> brightness. Therefore, several would be needed to light a wide area.
> As someone else mentioned, it would only take 3 Volts but many Amperes
> to do the job!
>
Yep.
> Perhaps the development of small many-Farad low voltage capacitors will
> enable the use of multiple LEDs, just as a high voltage capacitor is
> used with a xenon flash tube. The 3 Volt battery would charge the
> capacitor slowly, but the LED would discharge it quickly. The trick
> will be development of an efficient high current switching device!
>
There *are* already 1 Farad capacitors, the problem is that they are bigger
than coca cola cans, and they are used in large car stereos, along with
special alternators and special batteries.(A friend of mine in Kozani told
me that when I was making my thesis, a tube AM transmitter).



--
Tzortzakakis Dimitrios
major in electrical engineering
mechanized infantry reservist
hordad AT otenet DOT gr
 >> Stay informed about: I want a 400/500 f/5.6 IS/OS non-zoom lens . . . 

Eric Miller wrote:
> Alan Browne wrote:
>> More the reason. I just used 2000 mAh as a reference. See my amended
>> v. as I screwed up the volume calc on the first v.
>>
>> I can't find any NiMH in CR123 format, probably 'cause as 3V they
>> would need to be 2 NiMH in series which makes for poor recharging.
>>
>> Cheers,
>> Alan
>>
>>
>
> I don't doubt your calculations or reasoning, I just think that you have
> missed the point about SIZE. The CR123's are SHORTER. The flash that
> they would fit into could presumably be SMALLER. It would likely not
> flash as many times nor have as high a guide number as a 4AA flash or,
> perhaps, recycle as quickly, but it would be a flash not designed for
> wedding photographers. I was thinking of something simply made to fit
> smaller cameras and provide significantly better light output than
> on-camera flash without being bigger than the camera itself.

Well go forth and convince the camera co's!

Cheers,
Alan

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 >> Stay informed about: I want a 400/500 f/5.6 IS/OS non-zoom lens . . . 

Paul Coen wrote:
> Alan Browne wrote:
>> Paul Coen wrote:
>>
>>> Oddly enough, when you go to the sonystyle.com camera page, the link
>>> for the lenses is a picture of the 500mm Reflex. I would have figured
>>> they'd use one of the Carl Zeiss lenses.
>>
>> I don't think Carl Zeiss are much into really long FL's, and esp. not
>> CAT's.
>>
>
> They're not - I'm commenting on the odd choice of an image of the 500mm
> reflex as the image for the "lenses" category in general. I would have
> expected them to use an image of one of the snazzy new lenses.

Sony marketing on the SLR side has been a bit bizzare...

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-- e-meil: Remove FreeLunch.
 >> Stay informed about: I want a 400/500 f/5.6 IS/OS non-zoom lens . . . 

[A complimentary Cc of this posting was sent to
Alan Browne
<alan.browne DeleteThis @Freelunchvideotron.ca>], who wrote in article <fog80u$oqp$1@inews.gazeta.pl>:
> Sony marketing on the SLR side has been a bit bizzare...

I saw an explanation (do not know whether one can trust it): the plant
for A100 was for very-low-volume production. They could not market,
since the plant was using all its capacity anyway.

Same people said that the A700 plant is 66% of capacity of the
corresponding-level Canon model (20K vs 30K [per month?]). So the
marketing of A700 IS very different (but still kinda bizzare, I
agree...).

Hope this helps,
Ilya
 >> Stay informed about: I want a 400/500 f/5.6 IS/OS non-zoom lens . . . 

Tzortzakakis Dimitrios wrote:

>> Perhaps the development of small many-Farad low voltage capacitors will
>> enable the use of multiple LEDs, just as a high voltage capacitor is
>> used with a xenon flash tube. The 3 Volt battery would charge the
>> capacitor slowly, but the LED would discharge it quickly. The trick
>> will be development of an efficient high current switching device!
>>
> There *are* already 1 Farad capacitors, the problem is that they are bigger
> than coca cola cans, and they are used in large car stereos, along with
> special alternators and special batteries.(A friend of mine in Kozani told
> me that when I was making my thesis, a tube AM transmitter).

Actually, a typical 1F capacitor used in car audio systems is closer to
the size of a coffee can (though usually in a taller, narrower form factor.

The problem with this idea is that capacitor sizes are somewhat limited
by the laws of physics - capacitance, or the amount of energy that can
be stored, is a direct factor of the size of the plates and the
thickness of the dielectric. A multi-farad capacitor will ALWAYS have a
certain minimum size, there's just no getting around it.
 >> Stay informed about: I want a 400/500 f/5.6 IS/OS non-zoom lens . . . 

In article <fovaj6$e3u$1@registered.motzarella.org>,
Matt Ion <soundy106.RemoveThis@gmail.com> wrote:

> The problem with this idea is that capacitor sizes are somewhat limited
> by the laws of physics - capacitance, or the amount of energy that can
> be stored, is a direct factor of the size of the plates and the
> thickness of the dielectric. A multi-farad capacitor will ALWAYS have a
> certain minimum size, there's just no getting around it.

But, if you can make the dielectric thinner, you'll get more capacitance in
the same volume. Of course, as the dielectric gets thinner, the breakdown
voltage goes down. But that's just a matter of finding dielectrics which
are able to withstand greater voltage gradients before breakdown.

Bottom line, I'm not convinced that we've reached the limits of physics yet
when it comes to maximizing capacitance/volume ratios for any given voltage
rating.
 >> Stay informed about: I want a 400/500 f/5.6 IS/OS non-zoom lens . . . 

Matt Ion <soundy106.TakeThisOut@gmail.com> wrote:

> The problem with this idea is that capacitor sizes are somewhat limited
> by the laws of physics - capacitance, or the amount of energy that can
> be stored, is a direct factor of the size of the plates and the
> thickness of the dielectric. A multi-farad capacitor will ALWAYS have a
> certain minimum size, there's just no getting around it.

You could move from plates and dielectric to supraconducting
wire loops. Which is fun, except that they don't do unlimited
magnetic fields nor unlimited amounts of current ...

-Wolfgang
 >> Stay informed about: I want a 400/500 f/5.6 IS/OS non-zoom lens . . . 

[A complimentary Cc of this posting was sent to
Roy Smith
<roy.TakeThisOut@panix.com>], who wrote in article <roy-BE7936.18091713022008.TakeThisOut@70-1-84-166.area1.spcsdns.net>:
> But, if you can make the dielectric thinner, you'll get more capacitance in
> the same volume. Of course, as the dielectric gets thinner, the breakdown
> voltage goes down.

At some moment, tunnelling will start to matter.

> But that's just a matter of finding dielectrics which
> are able to withstand greater voltage gradients before breakdown.

And there ARE physical limits for this. Basically, they would give a
limit for stored-energy/volume of a capacitor (but, without taking
into consideration quantum effects and size of atoms, no limit for
capacitance/volume).

> Bottom line, I'm not convinced that we've reached the limits of physics yet
> when it comes to maximizing capacitance/volume ratios for any given voltage
> rating.

There is a lot of people (at least, a lot on r.p.d) who think that the
current state-of-art has some relationship to laws of physics. The
cases when this holds do exist, but are quite rare.

Hope this helps,
Ilya
 >> Stay informed about: I want a 400/500 f/5.6 IS/OS non-zoom lens . . . 

In article <j36c85-osm.ln1 DeleteThis @ID-52418.user.berlin.de>, ozcvgtt02
@sneakemail.com says...
-Matt Ion <soundy106 DeleteThis @gmail.com> wrote:
-
-> The problem with this idea is that capacitor sizes are somewhat limited
-> by the laws of physics - capacitance, or the amount of energy that can
-> be stored, is a direct factor of the size of the plates and the
-> thickness of the dielectric. A multi-farad capacitor will ALWAYS have a
-> certain minimum size, there's just no getting around it.
-
-You could move from plates and dielectric to supraconducting
-wire loops. Which is fun, except that they don't do unlimited
-magnetic fields nor unlimited amounts of current ...

except that coils are called inductors,
which are not at all like capacitors.
-
--Wolfgang
-

--
Bob Crownfield
crownfield DeleteThis @verizon.net
 >> Stay informed about: I want a 400/500 f/5.6 IS/OS non-zoom lens . . . 

"crownfield" <crownfield.TakeThisOut@verizon.net> wrote in message
news:MPG.221e6d583af8d4c69897cb@news.verizon.net...
> In article <j36c85-osm.ln1.TakeThisOut@ID-52418.user.berlin.de>, ozcvgtt02
> @sneakemail.com says...
> -Matt Ion <soundy106.TakeThisOut@gmail.com> wrote:
> -
> -> The problem with this idea is that capacitor sizes are somewhat limited
> -> by the laws of physics - capacitance, or the amount of energy that can
> -> be stored, is a direct factor of the size of the plates and the
> -> thickness of the dielectric. A multi-farad capacitor will ALWAYS have
> a
> -> certain minimum size, there's just no getting around it.
> -
> -You could move from plates and dielectric to supraconducting
> -wire loops. Which is fun, except that they don't do unlimited
> -magnetic fields nor unlimited amounts of current ...
>
> except that coils are called inductors,
> which are not at all like capacitors.
>
Depends on the frequency. At high frequencies, the adjacent windings of a
coil can display capacitance, and the spiral plates and dialectric of a
capacitor can display indutance.
ELI the ICEman can be very cruel at times.
 >> Stay informed about: I want a 400/500 f/5.6 IS/OS non-zoom lens . . . 

In article <fp2jj8$1go$1@aioe.org>, kwhart1.DeleteThis@verizon.net says...
-
-"crownfield" <crownfield.DeleteThis@verizon.net> wrote in message
-news:MPG.221e6d583af8d4c69897cb@news.verizon.net...
-> In article <j36c85-osm.ln1.DeleteThis@ID-52418.user.berlin.de>, ozcvgtt02
-> @sneakemail.com says...
-> -Matt Ion <soundy106.DeleteThis@gmail.com> wrote:
-> -
-> -> The problem with this idea is that capacitor sizes are somewhat limited
-> -> by the laws of physics - capacitance, or the amount of energy that can
-> -> be stored, is a direct factor of the size of the plates and the
-> -> thickness of the dielectric. A multi-farad capacitor will ALWAYS have
-> a
-> -> certain minimum size, there's just no getting around it.
-> -
-> -You could move from plates and dielectric to supraconducting
-> -wire loops. Which is fun, except that they don't do unlimited
-> -magnetic fields nor unlimited amounts of current ...
->
-> except that coils are called inductors,
-> which are not at all like capacitors.
->
-Depends on the frequency. At high frequencies, the adjacent windings of a
-coil can display capacitance, and the spiral plates and dialectric of a
-capacitor can display indutance.

they also have resistance,
but still caps and coils are not the same.

-ELI the ICEman can be very cruel at times.
-
-
-

--
Bob Crownfield
crownfield.DeleteThis@verizon.net
 >> Stay informed about: I want a 400/500 f/5.6 IS/OS non-zoom lens . . . 

crownfield <crownfield.DeleteThis@verizon.net> wrote:
> In article <j36c85-osm.ln1.DeleteThis@ID-52418.user.berlin.de>, ozcvgtt02
> -Matt Ion <soundy106.DeleteThis@gmail.com> wrote:

>-> The problem with this idea is that capacitor sizes are somewhat limited
>-> by the laws of physics [...]

> -You could move from plates and dielectric to supraconducting
> -wire loops.

> except that coils are called inductors,

Of course not. Nor are flywheels (some of which can release
all their energy in a single revolution).

Capacitors, flywheels, µ-SMES, ... are all power storage systems
capable of short term storage, and extremely rapid power release
--- in other words, what's needed for high-power and/or high-amp
flash units.

> which are not at all like capacitors.

Which matter why?

-Wolfgang
 >> Stay informed about: I want a 400/500 f/5.6 IS/OS non-zoom lens . . .