Quality lense... or a crap lense?

It's all about quality of image. Large zoom ranges often result in more distortion, lower contrast, less "punch" in the colours and worse fringing and flare. Professional zooms are also normally faster than their consumer counterparts. Faster lenses are orders of magnitude more difficult to make which results in the cost.

Of course for ultimate image quality and speed it's very difficult to beat prime lenses which don't zoom at all.

Edit to add: one more thing. The wider the lens the more difficult it is to make optics that will correctly focus the light onto the image sensor without massive amounts of distortion.

Good glass is not cheap. With high quality glass lenses comes a higher price tag and greater resolution, regardless of the zoom range. That combined with the speed of a lens, and the durability of its construction... make up its value in my opinion. Yes sacrifices do have to be made in image quality to achieve vast reaches of telephoto range, (each element of glass between the front and rear elements degrade the IQ a little bit or a lot, depending on their quality as well) but in a well built lens with high quality glass, the difference is negligible. But you will pay for it whether it is a 25mm prime or a 25-100mm f/2.8

As far as how can you tell what is a better lens? Read professional photographer's lens reviews, not the ones on camera store websites.

In general, it is difficult to diffract light over a long distance while maintaining quality. Fewer different lens glass elements is better.

Prime lenses (ie. 50mm fixed) are the best for quality. Zoom lenses give up quality for convenience much of the time.

The super wide and the super long range lenses a lot more expensive to manufacture -- that is the easiest answer.

The longer the zoom the larger the aperture value the cheaper the glass.

For example...

The Nikon 70-200mm f/2.8 VR is more expensive than the Nikon 80-400mm f.4.5 - 5.6 VR

Because the 70-200mm has the ability to open up the aperture to a large f/2.8 all the way through the focal length you would be getting a sharper photograph, better quality glass, heavier, better contrast, faster focusing etc.

However the 80-400mm may not have such a large aperture but it has a longer zoom for less money - your making scarifies but depending on the type of subjects you are photographing the scarifies may not be as serious.

An example of this maybe that a professional portrait / fashion photographer would probably have the 70-200mm and the kean wildlife photographer would probably go for the 80-400mm

...in my opinion anyway

Another thing is the maximum aperture a lens can have, which is what makes a lens capable of collecting more light. The fastest zoom lenses out there will open up to F/2.8 with constant aperture throughout the focal length (think 24-70 L, 16-35L, 70-200). The problem (aside from contrast, saturation, and distortion) with having an f/2.8 lens that can actually zoom from say 18 to 200 is that it will need to be the size of a Panzerbüchse.

eddx said:

The longer the zoom the larger the aperture value the cheaper the glass.

For example...

The Nikon 70-200mm f/2.8 VR is more expensive than the Nikon 80-400mm f.4.5 - 5.6 VR

Because the 70-200mm has the ability to open up the aperture to a large f/2.8 all the way through the focal length you would be getting a sharper photograph, better quality glass, heavier, better contrast, faster focusing etc.

However the 80-400mm may not have such a large aperture but it has a longer zoom for less money - your making scarifies but depending on the type of subjects you are photographing the scarifies may not be as serious.

An example of this maybe that a professional portrait / fashion photographer would probably have the 70-200mm and the kean wildlife photographer would probably go for the 80-400mm

...in my opinion anyway

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Actually, the 70-200 is not more expensive simply because it has the ability to open up to 2.8, it has a constant aperture whereas the 80-400 does not.
That is huge with zooms...well most lenses in general.

jessica. said:

Actually, the 70-200 is not more expensive simply because it has the ability to open up to 2.8, it has a constant aperture whereas the 80-400 does not.

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I thought I had made that point clear - obviously not, thanks for correcting me Jessica

camerark said:

My other question is really how to tell a good quality lens from a crap lense! Why are 12-24mm lenses so expensive while you can get a different lens with much more zoom range for the same price?

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Some things are hard (or expensive) to do with optics. Some the these are

• Make a lens with a focal length that is much less then the size of the sensor or film frame.
• Make a lens that has large diameter. In other word a lens that is "fast".
• A zoom lens with a wide rage of lenghts

But pros are sometimes willing to pay to lenes that do "hard" things

Sorry if I come off as condescending, but I'm making the assumption that you're pretty new to dSLR photography.

Previous posters have been pretty good explaining how a bigger zoom range means sacrifice in quality, but the main reason a lens costs a lot or a little is the aperture.

The wider a lens can open (i.e. the lower the "f number" AKA "f/" or "f-stop"), the better the photo in low light.

Those long-range zooms with variable and high f numbers? They don't work well at night. Or at all in many less-lit indoor situations; this is where the pro is willing to pay more.

I consider superior build quality a follow-up to superior aperture.

(note: there are other uses for a wide aperture. for ex, depth of field)

Maybe think about it like this, equate camera lenses to cars. Like we have all sorts of lenses, there are all sorts of cars.

Your run of the mill lens is your standard camry/malibu/accord. Nothing fancy, gets you where you and 4 others need to go. Likewise, you can get the same range but lens costs a lot more, well, did you want the Kia or the Bentley? Both will do the same thing, one just does a whole lot better, but as always you pay for the perfomance.

A Hummer H1, although it can be used to general purpose tasks, it is much more suited to going offroad and in places a car would never reach, or sink trying to get there. Think the super wide angle lens, a regular lens might get the shot but you may need to be a few miles away and even then the distance will reduce your quality.

A Corvette C6R is a high performance vehicle that will never be street legal and only seen on the race track. Think your f/2.8 telephone zooms, it doesn't matter where you are in the zoom range it holds the same aperture.

Then you can have your Audi R10 LMP1 diesel, super fast, super expensive, high tech this that the other, maybe that is your 600mm, 800mm lenses.

The more complex the lens, the higher quality the lens, the faster the lens, the more you pay for it. If you are taking photos for fun then missing a shot or four here and there isn't the end of the world, if you are being paid for your photos then one missed shot can be serious money.

jbernie said:

...Think your f/2.8 telephone zooms....

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I like my large f/2.8 telephone zoom just fine, thank you

I'm still at a stage in photography where I've got a couple of semi-expensive zoom lenses and a 50mm prime. You know what? That's all I need right now. You have to be pretty skilled to handle some of the more expensive lenses. Better quality, blah blah blah... I know. I can't afford it and I don't have enough skill yet. Works out great. When I have a real job, I'll make the upgrade to primes and large apertures and sherpas to carry around all my gear while I'm out in the wilderness. Right now I'm just an amateur, and that's just fine.

eddx said:

I thought I had made that point clear - obviously not, thanks for correcting my Jessica

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I'm sorry you probably did. I admit I may not have read your post as carefully as I should have. Actually I started crafting my response and a co-worker walked in so I was distracted and never hit send. But really you were clear. We'll have to discuss the "my Jessica" part though....do I get dinner out of being dubbed yours? I'm kinda hungry.