Are primes brighter and sharper than wide open zooms

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

- Siddhartha


In theory, zooms will always be somewhat below the quality of prime lenses.
Zooms typically have barrel distortion at one end of the zoom range, and
pincushion distortion at the other. Older zooms, especially those that did
not have decent multicoating, were more prone to flare and ghosting, because
of the light bouncing back and forth off the air-to-glass surfaces.

The margin of superiority of primes over zooms has narrowed, and many
photographers find the convenience and economy of one zoom versus several
primes to be more important than some slight degree of image degradation. I
have a couple of Pentax zooms in K-mount that do a credible job, and it
certainly is easier to carry two zooms than it is to carry 5 or 6 primes.
Thirty years ago, I bought a couple of third-party zooms for my M43 bodies,
and the results were just awful, relative to my SMC Takumar prime lens.
Colors had a grayish cast, saturation was less than on the OEM lens, the
aperture ring was operated in the reverse direction of my Takumar's (Pentax
does it "backwards"), the front element turned when the focusing ring was
moved, making polarizer use difficult, the lens front element was not the
standard Takumar 49mm or 58mm, making it necessary to buy filters just for
use in that lens, and the resolution was noticeably less than that of the
OEM Takumar.

The build quality was obviously less-good than the OEM lens. The focusing
was not nearly as smooth, the zoom ring was a bit on the tight side, the
lens barrel was not as sturdy and the lens lacked multicoating (this was 30
years ago). So, while I saved a few dollars, I got pretty much what I paid
for and no more. I ended up putting that zoom lens up on the shelf, where
it remains to this day, and I bought only OEM lenses after that. They cost
a bit more, but the level of satisfaction that I derived from them made up
for the higher price. And not a single one of the OEM lenses has failed, in
3 decades.

British landscape photographer and author Brian Bower noted that, while his
Leica R zoom lenses cost a lot more than non-OEM lenses, he felt that they
were a good value because they retained their accuracy after over a decade
of hard use. He noted in one of his books that the cheaper zoom lenses
might see the elements go out of precise adjustment and the zoom mechanism
might become very loose after a time, making it necessary to keep checking
the zoom ring to be certain that the zoom ratio has not changed from
whatever it was originally set to. Bower valued consistently good results
more than lower price. He made his living with those tools, and he had
little tolerance for lens failures.

My own take on it is that if the proposed use of the lens is of a very
casual nature, it is probably okay to go for the savings. But if top
performance and reliability are paramount, one really has to think about
whether the savings might be offset by potential future loss from
poorly-performing equipment. I would rather have only a couple of really
good lenses than a kit full of lenses of questionable reliability and
performance. It seems that, in my own case, virtually every time I have
tried to save money by cutting corners I ended up paying double.

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

- Siddhartha

I've heard it suggested that may high quality zooms are visually
indistinguishable from their prime equivalents - however both can usually
out-perform most photographers!

wrote:

The prime may be slightly brighter than the zoom, something which may
be more important in the motion-picture industry
They use a term called the "t stop" of a lens and it is a measure of
the light loss through a lens.
http://artsci-ccwin.concordia.ca/comm/lighting.htm
The difference could be as little as a third or as great as (or greater
than) a 2 stop difference between what the f-stop is and the t-stop,
while the DoF will be the same and sharpnes is likely to be less with a
zoom than a prime.

I would very much like to hear which particular lenses for DSLRs or
35mm SLRs produce a 2 stop reduction in illumination from that
expected at any given aperture.

You needn't list all of them, merely give some examples. ;-)

In real life still photography I don't believe it would be noticable
(the difference in brightness), because of a variety of factors.
I personally would not lose any sleep over it.

You wouldn't lose any sleep over a *two stop* reduction in
illumination? Either you are a very sound sleeper, or that reduction
simply doesn't exist. Or possibly both.

;-)

"Nostrobino" wrote:

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.

The use, or misuse, of the term "prime" is nothing new. The same
discussion was around in the 1960s and 70s. It wasn't resolved then
and probably never will be.

So don't blame the Internet. Blame the manufacturers who chose to use
this term as a marketing tool at various times in the last 50 years.

;-)

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?

No. f/2.8 tells you exactly how bright the lens is. (It's almost
like the old question about a pound of lead and a pound of feathers -
they do both weigh the same.)

- Will the prime be sharper wide open than the zoom at 28mm?

Probably, particuarly if both lenses are in the same price range. On
the other hand, there are lots of expensive zoom lenses that are
sharper than cheap fixed lenses.

-Joel

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"I would very much like to hear which particular lenses for DSLRs or
35mm SLRs produce a 2 stop reduction in illumination from that
expected at any given aperture."

2 stops is an awful lot, although I suppose some ancient zoom lenses
with lousy coatings might be that bad. One of the most complex zooms
I'm personally familiar with has about 40 elements, but nevertheless
suffers less than a 1-stop illumination reduction.

Brian

Yes, I'm sure the missuse of the term "prime lens" will go down in
history as one of the greatest tragedies of our generation ;-)

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

You make it sound like it's some kind of disease. In the grand scheme of
things, does it really matter? Languages are dynamic, and the meanings
of words are constantly changing. The original meaning of "prime" in the
photographic sense is just an invention anyway. Referring to the
dictionary I find no mention of lenses as related to the meaning of the
word "prime". Who is therefore to decide which usage is correct? You
apparently!

The first listing that I found at dictionary.com is...

"First in excellence, quality, or value"

I think therefore it's perfectly reasonable to refer to a high quality
FFL lens in this way.

Perhaps you should just "chill out" a little and stop preaching about
who or who isn't ignorant.


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.

In message ,
"Cockpit Colin" wrote:

I've heard it suggested that may high quality zooms are visually
indistinguishable from their prime equivalents

You can always bring out the difference in a large print or display, or
with teleconverters or extension tubes

- however both can usually
out-perform most photographers!

Not under good conditions.
--


John P Sheehy

Just some links you may want to check out...

http://photonotes.org/cgi-bin/entry.pl?id=Primelens
http://en.wikipedia.org/wiki/Prime_lens
http://www.absoluteastronomy.com/enc...prime_lens.htm

Please stop spreading misinformation. The first usage of a term is not
necessarily the correct one. If you start referring to zooms as "prime"
you're just going to make yourself sound stupid. Whatever you think it
meant originally, is not what it means now.

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.

N.