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Old Feb 19, 2009, 11:22 AM   #1
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What is the advantage of prime lenses? Is there any advantage to having a standard prime lenses & then getting an additional lens for wide angle as opposed to having an 18-55 lens for example?

Also if I am buying a telephoto lens, say 55-300 do they all come with the same apertures? Is it better to have ones with faster apertures but does that make it more expensive? What is the best aperture range to get for a reasonable price? It would be for a Pentax K200D if I decide to purchase the camera.
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Old Feb 19, 2009, 12:40 PM   #2
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In the "old days" (1970s & '80s), prime lenses were significantly sharper than zoom lenses. If you wanted the sharpest image, for a really nice crisp enlargement, you pretty much had to use a prime lens. Zooms were very convenient, but they tended to produce soft images. But recent improvements in computerized designs and more exacting manufacturing processes have largely erased those differences. It may still be true that a good prime lens can out-resolve a good zoom, but the difference is quite small. Most high quality modern day zooms are capable of producing very sharp images.

The kit lens that comes with the K200D is a very nice zoom lens, and is quite sharp. There are better lenses out there, but for about $100 it's really hard to beat the Pentax kit zoom. Zoom lenses do not all come with the same aperture, and you will pay in many ways for fast zooms (or fast primes, for that matter). They are expensive (sometimes outrageously so), they are heavy, and they are bulky.To pick an extreme example, a600mm f/2.8 lens will be about a foot and a half long, and will have a front element nearly the size of a dinner plate. Slower zooms frequently produce images that are just as sharp as faster lenses, but you have to use either a slower shutter speed, or a higher ISO setting. The slower zooms also will tend to produce deeper depth of field, which may or may not be desirable, depending on how you want the final shot to look.
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Old Feb 19, 2009, 2:57 PM   #3
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Fixed focal length lenses ('Primes') tend to be sharper than zoom lenses,have fewer moving parts so they tend to stay sharper, and have larger apertures so they allow shallower depths of field, and let in more light so you can shoot at lower ISO settings and/or faster shutter speeds.

Lenses of all focal lengths, both primes and zooms, are available with different maximum apertures, and generally, the larger the aperture the sharper it is but also the more expensive it is.

For low light/indoor photography, having a fast prime is a nice idea, especially if it doesn't cost a lot. But if you prefer to use flash anyway, then you won't have much use for it.
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Old Feb 20, 2009, 12:32 AM   #4
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I'm probably the last person that should be answering this question! I have a mix of both prime and zoom lenses, some consumer quality and some fast, high quality.

Aperture controls the amount of light that hits the sensor - it's the leaves that are in a lens that open and close, allowing you to control how much light is allowed in. This influences two things - the shutter speed and the depth of field (how much of a scene is in focus). If you have a large aperture (opening), more light can come in so you have to use a faster shutter speed to get a proper exposure. This works well for someone who's shooting sports and wants to freeze the action. But its not helpful if you want to shoot a silky smooth waterfall, or show motion blur and want to use a slower shutter speed.

A large lens opening also means that you have a smaller distance that's in focus (depth of field). That's great if you are trying to separate a face from a background, but not good if you want to have two subjects separated by 10 or 15 feet and you want both in focus.

Aperture is indicated by the f: number - something like f2.8 or f1.4 or f5.6 etc. The smaller the number, the larger the aperture (it's actually a ratio but let's not get into the technical side any more).

As mtnman pointed out, lenses with large openings are bigger, heavier and more expensive (there's more glass involved to get that bigger opening). If you are taking pictures outside all the time, then you might not need a fast lens. But if your primary purpose is taking pictures in museums, then you'll need something that will let in the most light possible.

So the answer to your question about aperture is that it depends on what you are going to do, how much money you want to spend, and how heavy a lens do you want to carry. An expensive, big, heavy fast lens like my DA*50-135 f2.8 might not out-perform my humble DA 55-300 f4-5.8 consumer lens at f11, but it can give me reasonable shutter speeds indoors, where the DA 55-300 can't. On the other hand, who wants to go hiking with more weight , 15.5 oz. compared to 1.5 lbs, and the DA 55-300 is a lot longer than the faster DA* lens.

As far as primes vs. zooms - the better prime lenses I have outperform my zooms, but not all primes will outperform a modern zoom. You really need to take them on a case-by-case basis, rather than making a blanket statement. I happen to like primes, but they are inconvenient at times and not for everyone. I do mostly macro and landscape, which means I shoot slowly and take my time with things. I don't mind changing lenses often. If I were shooting sports then I'd want the versatility of a zoom lens. So the zoom vs. prime depends on personal preference and type of photography you plan on doing - there's really not a blanket "one is better than the other" answer.
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Old Feb 20, 2009, 7:50 AM   #5
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jvanwees wrote:
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What is the advantage of prime lenses? ...
There is no hard and fast answer; one would exist only when comparing a specific zoom to a specific prime. There are general trends:

1. Primes tend to be faster, though generally only when comparing "normal" and longer focal lengths. The fastest APS-c format mid-range zooms (approx 18-50mm) are around f/2.8. Common 50mm lenses are f/1.8 and f/1.4, 1 1/3 to 2 stops faster. On the other hand, few primes in the 20mm range are faster than f/2.8.

2. Primes tend to have less rectalinear (barrel and pincushion) distortion. This was a critical difference back when film was dominant but much less so with digital.

3. Primes tend to be smaller and lighter.

4. Primes used be sharper. Today, this is no longer the case in general. Zooms generally deliver very similar resolution numbers while primes, having fewer elements, frequently control flare better, which leads to an increased perception of "sharpness". This is generally a very subtle difference.
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Old Feb 20, 2009, 9:07 AM   #6
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What they all said! ^^^^^^:roll: In summary...when getting a camera..get the Kit Lens and a medium to long zoom to start with. With the 18-55 and the 55-300mm lens set, you cover most things needed right off the bat. For indoor low light situations get the FA 50mmf/1.4. If you are a beginner get all auto focus zooms to begin and later as Lens Buyer's Addiction grabs a hold on you (LBA for short) you can expand your lens base or collection or museum pieces, or how ever you decide to describe them to your spouse.

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Old Feb 20, 2009, 11:10 AM   #7
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dwig wrote:
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1. Primes tend to be faster, though generally only when comparing "normal" and longer focal lengths. The fastest APS-c format mid-range zooms (approx 18-50mm) are around f/2.8. Common 50mm lenses are f/1.8 and f/1.4, 1 1/3 to 2 stops faster. On the other hand, few primes in the 20mm range are faster than f/2.8.
Just for the heck of it, I did a little research.

I did a search on Adorama for Wide Angle and Normal lenses (Primes) (without specifying a mount.) I found 37 lenses that had maximum apertures larger than f/2.8, lots of lenses with maximum apertures of exactlyf/2.8, but only one lens with a maximum aperture smaller than f/2.8.

I also did a search for Wide Zooms and Standard Zooms. I found no lenses with apertures larger than f/2.8, 23 lenses with constant apertures of f/2.8, and lots of lenses with maximum apertures smaller than f/2.8.

So I think your statement that "... few primes in the 20mm range are faster than f/2.8." is incorrect and misleading.

Clearly, a maximum aperture of f/2.8is common ground for bothPrimes and Zooms, but it is also a dividing line between them.

dwig wrote:
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4. Primes used be sharper. Today, this is no longer the case in general. Zooms generally deliver very similar resolution numbers while primes, having fewer elements, frequently control flare better, which leads to an increased perception of "sharpness". This is generally a very subtle difference.
I don't agree that, in general, Zooms are as sharp as Primes, but I'll leave that alone.

What I will say is that fewer elements also means less chance of chromatic aberration, and since, asyou said, Primes have fewer elements, they would also, in general, have less chromatic aberration, which will also lead to 'an increased perception of "sharpness".' And that difference isn't very subtle.
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Old Feb 20, 2009, 2:26 PM   #8
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bigdawg wrote:
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What they all said! ^^^^^^:roll:* In summary...when getting a camera..get the Kit Lens and a medium to long zoom to start with. With the 18-55 and the 55-300mm lens set,* you cover most things needed right off the bat. For indoor low light situations get the FA 50mmf/1.4. If you are a beginner get all auto focus zooms to begin and later as Lens Buyer's Addiction grabs a hold on you (LBA for short) you can expand your lens base or collection or museum pieces, or how ever you decide to describe them to your spouse.*

Dawg
I think that Dawg's strategy is a good one. With 2 good zooms, you can sample all the focal lengths that are included in a "super zoom" bridge cam (27-450mm in 35mm eq). While you're using these, you'll discover the particular FLs that you use the most, and you can start doing research as to the best primes that are available at these or similar FLs.

You'll also discover where you need more lens speed, or where you'd want more control of DOF, or where you'd like more sharpness. Once you've determined your needs for what you like to shoot, it's relatively easy to determine where to put your money into lenses. Pentax has the advantage of having lots of older, manual focus lenses that you can try out for FL and speed, without having to spend a lot of money. Once you've determined your needs specifically, you can look for the right deal on the specific modern lens that you want, or stand pat with the MF version.

Personally, I mainly shoot birds, so I concentrate on longer FLs. I've chosen to go with a few zooms to cover the wide end, and use fast primes, sometimes with TCs to cover the long end. Many more shoot wide as a normal course, and will choose a variety of wide primes and go with a good general purpose long zoom to cover the tele end when they want it. Neither is wrong, it just a matter of concentrating on what you like to shoot.

Scott
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Old Feb 20, 2009, 6:29 PM   #9
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Quote:
... Just for the heck of it, I did a little research.

I did a search on Adorama for Wide Angle and Normal lenses (Primes) (without specifying a mount.)
which would have included many lenses 28mm and longer which is where the faster lenses exist making the results irrelavent when discussion roughly 20mm lenses ...

Quote:
... So I think your statement that "... few primes in the 20mm range are faster than f/2.8." is incorrect and misleading.
I don't think you would have that opinion if you did a proper survey and limited you search for primes to those of about 20mm FL, say 16-22mm.
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Old Feb 20, 2009, 7:14 PM   #10
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TheOP wasn't talking about "20mm" lenses, you were. jvanwees was talking about "having a standard prime lenses & then getting an additional lens for wide angle." That's why Ithink your statement is incorrect and misleading.
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