[OT] eBay: Another Unbelievable Item Description

Jim Phelps wrote:
"Alan Browne" wrote in message
news
Jim Phelps wrote:


How about this one. I especially like the technical discussion on "fast
lens". Just how does that lens make the light be _absorbed_ at a _faster
rate_? Was Einstein wrong and light can be accelerated beyond the speed
of

While the wording in the post is clumsy and ill informed, rate in this
case means "how much in how much time", so it is true that an f/2.8
aperture takes in more light than an f/4.0 lens in a given time.
Reciprocity refers.



Alan,

In the description the seller says "... more light ... at a faster
rate..." While I agree a larger lens opening will allow more light to
transit the lens (volume - what everyone is saying), it will not do so at a
faster rate (velocity - what I am saying). The rate is fixed at the speed
of light and the photons do not transit the lens and accelerate. As far as
I know, you cannot accelerate light beyond the speed of light (Warp Factor
1+ only exists in a certain TV programs).


rate means n/time in this case. When talking about cars, it means the
car covers so many km/unit time (eg 120 km/hour). 10 cars travelling
in a bunch don't go 1200 km distance... but they do cover 1200 car-km.

An aperture that has twice the surface allows twice as many photons per
unit time. So it is faster at delivery (at its rear element).

You're a factory manager. You expect a supplier to to put 1000 units of
his product at your receiving dock every 2 hours. You don't care if he
uses 1 huge truck or 5 small trucks. But he has to put those 1000 units
there on time. His trucks all travel at 90 km/hr.

And so on, as I and others have tried to make clear.

rate = n/time.
Velocity = dist/time.

Both are "faster" as n or dist go up.

--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: there's no such thing as a FreeLunch.

Jim Phelps wrote:
"Alan Browne" wrote in message
news
Jim Phelps wrote:


How about this one. I especially like the technical discussion on "fast
lens". Just how does that lens make the light be _absorbed_ at a _faster
rate_? Was Einstein wrong and light can be accelerated beyond the speed
of

While the wording in the post is clumsy and ill informed, rate in this
case means "how much in how much time", so it is true that an f/2.8
aperture takes in more light than an f/4.0 lens in a given time.
Reciprocity refers.



Alan,

In the description the seller says "... more light ... at a faster
rate..." While I agree a larger lens opening will allow more light to
transit the lens (volume - what everyone is saying), it will not do so at a
faster rate (velocity - what I am saying). The rate is fixed at the speed
of light and the photons do not transit the lens and accelerate. As far as
I know, you cannot accelerate light beyond the speed of light (Warp Factor
1+ only exists in a certain TV programs).


rate means n/time in this case. When talking about cars, it means the
car covers so many km/unit time (eg 120 km/hour). 10 cars travelling
in a bunch don't go 1200 km distance... but they do cover 1200 car-km.

An aperture that has twice the surface allows twice as many photons per
unit time. So it is faster at delivery (at its rear element).

You're a factory manager. You expect a supplier to to put 1000 units of
his product at your receiving dock every 2 hours. You don't care if he
uses 1 huge truck or 5 small trucks. But he has to put those 1000 units
there on time. His trucks all travel at 90 km/hr.

And so on, as I and others have tried to make clear.

rate = n/time.
Velocity = dist/time.

Both are "faster" as n or dist go up.

--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: there's no such thing as a FreeLunch.

"Eric Miller" wrote in message
news

"Bob Hickey" wrote in message
...

"Chris Brown" wrote in message
...
In article ,
Jim Phelps wrote:

That's technically correct. If a square millimetre of film absorbs
light
at
the rate of N photons per second with an f/4 lens, then an f/2 lens
will
allow the same piece of film to absorb 4N photons per second.
That's like saying that if a Lincoln and VW travel from point A to B
at
exactly the same speed, the Lincoln is much faster. It's not; there's
just
twice as much of it. Bob Hickey



Actually, if the transfer of "it" is the issue, then the VW would have to
make two trips to accomplish the same function, and presumably take twice
the time, assuming you are correct and there is "twice as much of "it" in
the Lincoln," whatever, "it" is.

Eric Miller

Ok, scratch the Lincoln/VDub gag. Suppose you have two teles of
the same focal length; but one is a modern short barrel and the other is one
of those old Spiratone bazookas with a giant front element. The big front
will cause the photons entering at the edges to make more turns, and
therefore take longer to get thru the aperture. Ergo, it's slower.
OR: One 200 tele has only 5 multicoated elements, while another, a zoom,
has about 14 or so mostly uncoated elements. The short one will only lose
about 20%: negligable. The zoom, losing 4% per surface, will lose 112% of
it's light. Not only is that impossible, it's also a lot and bad arithmatic.
Bob Hickey

"Eric Miller" wrote in message
news

"Bob Hickey" wrote in message
...

"Chris Brown" wrote in message
...
In article ,
Jim Phelps wrote:

That's technically correct. If a square millimetre of film absorbs
light
at
the rate of N photons per second with an f/4 lens, then an f/2 lens
will
allow the same piece of film to absorb 4N photons per second.
That's like saying that if a Lincoln and VW travel from point A to B
at
exactly the same speed, the Lincoln is much faster. It's not; there's
just
twice as much of it. Bob Hickey



Actually, if the transfer of "it" is the issue, then the VW would have to
make two trips to accomplish the same function, and presumably take twice
the time, assuming you are correct and there is "twice as much of "it" in
the Lincoln," whatever, "it" is.

Eric Miller

Ok, scratch the Lincoln/VDub gag. Suppose you have two teles of
the same focal length; but one is a modern short barrel and the other is one
of those old Spiratone bazookas with a giant front element. The big front
will cause the photons entering at the edges to make more turns, and
therefore take longer to get thru the aperture. Ergo, it's slower.
OR: One 200 tele has only 5 multicoated elements, while another, a zoom,
has about 14 or so mostly uncoated elements. The short one will only lose
about 20%: negligable. The zoom, losing 4% per surface, will lose 112% of
it's light. Not only is that impossible, it's also a lot and bad arithmatic.
Bob Hickey

"Bob Hickey" wrote:

The zoom, losing 4% per surface, will lose 112% of
it's light. Not only is that impossible, it's also a lot and bad arithmatic.
Bob Hickey

No, just someone that doesn't understand percentages.

The first glass would lose 4% leaving 96%. The second would lose 4%
of 96% leaving. 92.16%. The third would lose 4% of 92.16% leaving
88.4% and so on.

Scott Peterson

--
A meeting is an event at which the minutes
are kept and the hours are lost.

364/601

I thought you were in jail.

Eric Miller

"Scott Peterson" wrote in message
...
"Bob Hickey" wrote:

The zoom, losing 4% per surface, will lose 112% of
it's light. Not only is that impossible, it's also a lot and bad
arithmatic.
Bob Hickey

No, just someone that doesn't understand percentages.

The first glass would lose 4% leaving 96%. The second would lose 4%
of 96% leaving. 92.16%. The third would lose 4% of 92.16% leaving
88.4% and so on.

Scott Peterson

--
A meeting is an event at which the minutes
are kept and the hours are lost.

364/601

"Eric Miller" wrote:

I thought you were in jail.

I thought that joke was funny the first few dozen times I heard it
too. Now I just have trouble understanding how, after 2 years of this
crap, someone could think this could be original.....or funny.



Scott Peterson

--
Those who can make you believe absurdities
can make you commit atrocities.
---Voltaire

565/603