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04-20-2009, 07:55 AM   #1
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Prime lenses

Another basic question:
I have a good idea of the concept but just in case I'm missing something:
What exactly is a "prime" lens or what makes a lens "prime"? Are there specific parameters for that?

Thanks,

04-20-2009, 08:01 AM   #2
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It's not quite like 'prime' rib! It refers to a lens with a fixed focal length. Zoom lenses have a variable focal length.

Al
04-20-2009, 10:02 AM   #3
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the previous poster is correct i.e. a lens with fixed focal length (single focal length) is called prime. please visit the lens review database here to get an idea of different focal length primes that are available for pentax. usually it is reported/perceived that prime lenses have better optics resulting in better pictures
04-20-2009, 11:01 AM   #4
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Thanks, I was under the impression that a prime was not only fixed focal lens but also very fast (f2 or less) and a "premium" pro lens.

Thanks,

04-20-2009, 11:22 AM   #5
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QuoteOriginally posted by ismaelg Quote
Thanks, I was under the impression that a prime was not only fixed focal lens but also very fast (f2 or less) and a "premium" pro lens.
That's probably a common assumption because in the old days, you could indeed count on primes to be faster than than zooms and higher quality as well. And of course, to a large extent, it's still true today - "most" primes *are* faster and better than "most" zooms. But there are faster and better zooms available now than ever before, and relatively fewer primes that are faster than f/2.8.
04-20-2009, 11:37 AM   #6
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QuoteOriginally posted by ismaelg Quote
Thanks, I was under the impression that a prime was not only fixed focal lens but also very fast (f2 or less) and a "premium" pro lens.
Well, I guess you could say there are primes and then there are primo primes but that's subjective. ;~)

Last edited by dadipentak; 04-20-2009 at 11:47 AM.
04-20-2009, 08:19 PM   #7
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A lens is a tube of compromises. The more you put in one end of the tube the more bad thing squirt out the other end.

As a zoom lens has to compromise across a range of focal lengths and a prime lens only one so the lens can have less compromises on the other things about a lens. This usually means a prime can be smaller, faster, lighter with better IQ and often cheaper. With top of the line primes the other things are optimized as much as possible at the cost of price.

With more modern computers to design lenses and better tradeoff of the compromises, some zooms can have IQ close to prime lenses. These usually have a more limited zoom range and usually bigger, heavier and slower then prime lenses. Making these zooms faster makes them even bigger, heavier and more expensive. I love my DA* 50-135 but next to my FA-77 it is a giant. The FA-77 is still a little fast with a little better IQ and cheaper.

Both zooms/prime lenses have their uses and one can be better to use then the other.

DAZ
04-30-2009, 09:43 AM   #8
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English is a funny language. Photo jargon is a funnier dialect. In common usage, ZOOM means, go fast. But many zoom (variable focal length) lenses are slow. POWER ZOOM should mean, go faster. But many powered zooms move rather slowly. Funny, funny. But VARIFOCAL just ain't got the marketing pizzaz of ZOOM.

In common usage, MACRO means big and MICRO means small. But macro lenses and attachments are used for capturing images of small stuff, while microscopes go after even smaller stuff. And many 'macro zoom' lenses can hardly do small stuff at all, let alone do them fast or well. On several of my zooms (both short and long), 'macro' means that close focus is 1.5M (5 feet) and magnification is 1:5. Funny, funny.

In common usage, PRIME means, very good. But many cheap prime (fixed focal length) lenses are rather bad. A bad prime lens is not like a bad prime rib -- with the lens, the sh!t stays with you. Lensmakers should honestly (HAH!) label some of their crud as sub-primes, like bad loans. But they won't, so we're stuck with it. Funny.

04-30-2009, 10:04 AM   #9
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I don't know for sure how singular-focal-length lenses became known as primes. It seems quite possible to me that the term wasn't necessarily because of quality but instead had to do with alternate meanings of 'prime', such as 'cardinal', 'principal', 'chief'.

There was a time when there were bascially no variable-focal-length lenses available--at this point in time, perhaps there were no "primes", they were just called "lenses". Lenses were pretty much built with standardized principal focal lengths (20/24/28/35/50/85/etc, though there were some exceptions). It seems to me that when zooms appeared in the marketplace these single focal length lenses may have been considered the basics and may have contributed to the application of the term 'prime'. Possibly someone much older than me (or with a better sense of camera history) who remembers when the term first became common has a better idea of the origin of the term.

Anyway, it's a theory.
04-30-2009, 10:10 AM   #10
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QuoteOriginally posted by RioRico Quote
English is a funny language. Photo jargon is a funnier dialect. In common usage, ZOOM means, go fast. But many zoom (variable focal length) lenses are slow. POWER ZOOM should mean, go faster. But many powered zooms move rather slowly. Funny, funny. But VARIFOCAL just ain't got the marketing pizzaz of ZOOM.

.
You are so right about the Marketing Pizzaz of the word Zoom!!!

Can you imagine the Mazda Jingle if they used

"Varifocal Varifocal Varifocal...."

instead of...

"Zoom Zoom Zoom..."

It's just not as catchy
04-30-2009, 11:51 AM   #11
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I always imagined the use of the word "prime" to describe single-focal-length lenses is related to the use of "prime" in mathematics - it refers to a number that has no other divisors except 1 and itself. Somehow, this seems similar to the idea of a lens that has no other focal lengths, even though it's not really the same.

BTW, the next question is, how do so many people become confused into thinking "zoom" means telephoto? Actually, that seems reasonably self-evident: most zoom lenses people are familiar with "start" in the wide or normal range, and the act of "zooming" is the act of moving into telephoto territory. And when judging P&S cameras, a larger zoom range (in "X" factors - 12X, etc) generally translates into more range on the telephoto end.
04-30-2009, 12:44 PM   #12
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QuoteOriginally posted by Marc Sabatella Quote
BTW, the next question is, how do so many people become confused into thinking "zoom" means telephoto? ... And when judging P&S cameras, a larger zoom range (in "X" factors - 12X, etc) generally translates into more range on the telephoto end.
I would dearly love to see an ultrawide zoom PNS cam, but I think makers are finessing that with panorama features, stitching together a few normal- or slightly-wide-aspect shots. We know that's not the same. I recall that Kodak had a baby with two lenses, a wide and a tele, to give extended range without the megazoom compromises.

Who was it, Ricoh, Panasonic? Someone had a PNS with a fixed 21mm-equiv lens, but that doesn't give a lot of flexibility. How about a quiet 8mpx PNS with fast rectilinear 10-50- or 12-96-equiv glass, eh? Yeah, like *that* would sell... [8mpx 2/3" sensor would have pixel density under 14mpx/cm2, should be pretty quiet. Engineering the lens shouldn't be impossible. But I ain't holding my breath.]
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