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Are primes brighter and sharper than wide open zooms



 
 
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  #31  
Old September 29th 05, 09:21 AM
Tony Polson
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Eugene wrote:

I don't think it has anything to do with the internet really. They've
been called prime lenses for as long as I can remember, and yes I do
pre-date the Internet ;-)



If only it was as simple as referring to all fixed focal length lenses
as "prime" lenses. Most subscribers to this newsgroup probably aren't
old enough to recall that some manufacturers used the term "prime" to
refer to a high quality subset of their fixed focal length lenses.

What made a particular fixed focal length lens design a "prime" lens
was not clear. Why other fixed focal length lenses were not described
as "prime" lenses was even less clear. But what is clear is that
assuming all fixed focal length lenses were referred to as "prime"
lenses is wrong. It was marketing, pure and simple.

Since there is no accepted definition of a "prime" lens we should just
drop the term, as it serves only to confuse.

I like the idea of FFL and VFL, especially as so many VFL optics are
not true zooms because they do not hold focus when zoomed. They are
often termed vari-focal lenses (also "VFL"), which term could be
extended to include the true zooms.

FFL and VFL has my vote.

;-)

  #32  
Old September 29th 05, 10:08 AM
Eugene
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OK, I stand corrected. This does make sense. Actually now that I think
about it I don't tend to use the terms "prime" and "zoom" much anyway.
I'd nearly always just refer to the specific lens type. Like I'd just
say 50mm f1.4 rather than 50mm prime. Adding "prime" is kind of
redundant. If only one focal length lens is given then it's obvious I'm
not talking about variable focal length.

Also I think there would be very few situations where lumping everything
into 2 distinct groups would make sense. For example "zoom" could
equally refer to an EF-S 18-55, as it could to an EF 70-200 f2.8 L.
Aside from the fact that both lenses can change focal lengths, they
really have nothing much else in common. They serve entirely different
purposes and an entirely different market. Likewise "prime" (meaning
FFL) could equally refer to a 7mm circular fisheye, or a 1200mm
super-telephoto.

Grouping lenses by focal length ranges makes more sense, ultra-wide,
wide-angle, medium-telephoto, super-telephoto etc. FFL and VFL, while
correct and non-ambiguous are also I think too broad to be generally useful.

OK, well I wont use the term "prime" or "zoom" anymore as I can see that
they really don't add a lot of value.


If only it was as simple as referring to all fixed focal length lenses
as "prime" lenses. Most subscribers to this newsgroup probably aren't
old enough to recall that some manufacturers used the term "prime" to
refer to a high quality subset of their fixed focal length lenses.

What made a particular fixed focal length lens design a "prime" lens
was not clear. Why other fixed focal length lenses were not described
as "prime" lenses was even less clear. But what is clear is that
assuming all fixed focal length lenses were referred to as "prime"
lenses is wrong. It was marketing, pure and simple.

Since there is no accepted definition of a "prime" lens we should just
drop the term, as it serves only to confuse.

I like the idea of FFL and VFL, especially as so many VFL optics are
not true zooms because they do not hold focus when zoomed. They are
often termed vari-focal lenses (also "VFL"), which term could be
extended to include the true zooms.

FFL and VFL has my vote.

;-)

  #33  
Old September 29th 05, 10:15 AM
Tony Polson
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Eugene wrote:

Perhaps my comments were a bit harsh. I just took offense to the
suggestion that it was ignorant to use the widely accepted and
understood term "prime lens".



But "prime lens" is NOT a "widely accepted and understood term".

Because of the history of its use, it is essentially ambiguous. It
has only been used as a descriptor for all fixed focal length lenses
in recent times, and only by people who are unaware of its prior
usage, which was as a descriptor for a "high quality" subset of fixed
focal length lenses. You might be too young to recall this.

There was no accepted definition of which fixed focal length lenses
were "prime" and which were not. It was merely an attempt by
marketing people to promote some lenses as being "better" than others,
the implication being that one brand was "better" than another because
of the "high quality" of their "prime" lenses.

The terms "high quality", "better" and "prime" are all essentially
meaningless unless backed up with something more objective, repeatable
and reliable. As we all (should) know, comparisons between lenses are
qualitative at best.

The most commonly used "objective" comparator - MTF - was never
intended for making such comparisons. It was intended as an aid to
lens designers and nothing more. As a result it misleads far more
than it ever informs, and those who claim it is of any real value when
comparing photographic lenses are suffering from delusions.


  #34  
Old September 29th 05, 10:29 AM
Chris Brown
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In article ,
Tony Polson wrote:

Since there is no accepted definition of a "prime" lens we should just
drop the term, as it serves only to confuse.


Feel free to go ahead. The rest of the world will carry on using it. You're
tilting at windmills.
  #35  
Old September 29th 05, 11:11 AM
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On Wed, 28 Sep 2005 22:29:43 -0700, "Brion K. Lienhart"
wrote:

Randall Ainsworth wrote:

In article . com,
Siddhartha Jain wrote:


Given two lenses, one a prime (say 28mm) and the other a zoom (say
28-75mm) and both with an aperture of f2.8 -
- Will the prime be brighter than the zoom because it has fewer lens
elements?
- Will the prime be sharper wide open than the zoom at 28mm?

Ofcourse, a lot will depend on the particular makes and models being
compared but is there a rule of thumb?



F/2.8 lets the same amount of light through regardless of the lens
design. F/2.8 is f/2.8.


Nope. F:2.8 is solely based on the size of the lens. Obsidian is glass,
you can grind it into a lens shape, but if you use it as an element in a
lens, you're going to get some reallllllly slow shutter speeds. Of
course that's an extreme case, the difference between plain old glass
glass, and exotic flouro-silicates is only a few fractions of a percent.


So what was your point in bringing up a special case ulikely
to be implemented?
  #37  
Old September 29th 05, 01:44 PM
Randall Ainsworth
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In article , Brion K. Lienhart
wrote:

Nope. F:2.8 is solely based on the size of the lens. Obsidian is glass,
you can grind it into a lens shape, but if you use it as an element in a
lens, you're going to get some reallllllly slow shutter speeds. Of
course that's an extreme case, the difference between plain old glass
glass, and exotic flouro-silicates is only a few fractions of a percent.


An f/2.8 lens is going to allow a specific amount of light to go
through regardless of what kind of glass it's made of.
  #38  
Old September 29th 05, 01:50 PM
no_name
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Nostrobino wrote:

"Siddhartha Jain" wrote in message
ups.com...

Nostrobino wrote:

Zoom lenses ARE prime lenses, notwithstanding the now-popular misusage of
"prime."

A prime lens is the camera lens as distinct from some other lens or
lenticular device (close-up lens, tele converter, etc.) used with it. It
has
meant that since long before zoom lenses became commonplace, and
therefore
no need to use another term to mean "non-zoom."

"Prime" is properly used in the sense of primary, main, chief or
original--all dictionary definitions for "prime."

There is NO dictionary definition for "prime" which means fixed focal
length
or single focal length, or fixed or single anything else.

It would be nice if this nonsensical misusage, which obviously is based
on
someone's misunderstanding of the term some years ago (and then spread
like
cancer through the power of the Internet) could be stamped out. Surely
"FFL"
is at least as easy to type as "prime" anyway, and there never was any
reason other than shortness to replace "fixed focal length" with the
incorrect term.


I am aware of the mis-usage of the term *prime* and so guilty of
propogating the mis-usage but I feel its time the FFL camp realised
that there is no turning back.



Well, not necessarily, though of course the more people who misuse the term,
the harder it will be to correct it.

Most people do not want to use wrong terminology since it makes them look
ignorant. In the case of "prime" being used to mean FFL, this has only
spread because readers who have not seen the term before, and then see it
used by people they assume are knowledgeable, naturally adopt it themselves.
Thus newbies are caught up in the misusage and (perhaps partly because they
feel using jargon will make them look knowledgeable too), contribute to the
spread.

Some will continue to use it anyway, but others will drop it (and some have
dropped it) when the error is pointed out to them.

N.



Just because "popular usage" may not appear in a particular dictionary
does not constitute "misuse".

If you speak of a prime lens to photographers, they know what you're
talking about.

Perhaps this should be continued in rec.english.language.anal.purists

  #39  
Old September 29th 05, 01:57 PM
no_name
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Tony Polson wrote:

Eugene wrote:

Perhaps my comments were a bit harsh. I just took offense to the
suggestion that it was ignorant to use the widely accepted and
understood term "prime lens".




But "prime lens" is NOT a "widely accepted and understood term".


Who here does not understand what is meant when the term "prime lens" is
used?

A show of hands please?
  #40  
Old September 29th 05, 02:00 PM
no_name
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John A. Stovall wrote:

On 28 Sep 2005 07:33:55 -0700, "Siddhartha Jain"
wrote:


Hi,

Given two lenses, one a prime (say 28mm) and the other a zoom (say
28-75mm) and both with an aperture of f2.8 -
- Will the prime be brighter than the zoom because it has fewer lens
elements?
- Will the prime be sharper wide open than the zoom at 28mm?

Ofcourse, a lot will depend on the particular makes and models being
compared but is there a rule of thumb?



Rule of Thumb: A prime at any focal length and wide open is better
than a zoom at any focal length wide open.


Except when it's not ... like a really well made fast zoom lens being
compared to a really poorly made slow prime lens.
 




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