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09-02-2010, 02:42 AM   #1
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Aspherical lenses any good?

These things look compact, there HAS to be a downside, or everyone would be using them, especially the 28-200mm lenses.

So what is the downside?

09-02-2010, 05:01 AM   #2
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What are you refering to exactly? Most lenses have aspherical elements in them, but I'm pretty sure that's not what you are refering to.

For the record, an aspherical element in a lens helps reduce spherical aberration, a phenomenon unavoidable with any lens (not necessarily a camera lens) that has a spherically curved surface. Light will not be focused on the exact same spot if it goes through the center or the sides of the lens, degrading the resolution. Aspherical elements, when well made, help reduce this effect and improve the resolution.
09-02-2010, 11:36 AM   #3
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QuoteOriginally posted by bdery Quote
What are you refering to exactly? Most lenses have aspherical elements in them, but I'm pretty sure that's not what you are refering to.

For the record, an aspherical element in a lens helps reduce spherical aberration, a phenomenon unavoidable with any lens (not necessarily a camera lens) that has a spherically curved surface. Light will not be focused on the exact same spot if it goes through the center or the sides of the lens, degrading the resolution. Aspherical elements, when well made, help reduce this effect and improve the resolution.
A lens like this:
28-200, and its so short. the lens extends to zoom instead of you moving a slide back and forth to zoom.
Is something wrong with these that EVERYONE doesnt have just one in their lens collection?
09-02-2010, 12:37 PM   #4
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Hey! That's my shot...

Good to know that my photograph of my FA 28-200mm is being used without my prior permission.

09-02-2010, 01:02 PM   #5
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I feel like I suddenly walked into a parallel dimension...
09-02-2010, 01:05 PM   #6
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I'm confused. I feel like someone is asking me, "Are Chevys fast?". Uh, well......yes........and no.

As far as a I know, aspherical elements are present in many, MANY lenses. It's not a specific "type" or "brand" of lens. To my knowledge, the "aspherical" part is simply the shape and creation of one of the glass elements within the lens.
09-02-2010, 01:42 PM   #7
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I have an aspherical lens (its more of a cylinder shape) with an aspherical element and I have to zoom by walking back and forth.

What is the downside?
09-02-2010, 08:05 PM   #8
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QuoteOriginally posted by Rory Quote
I'm confused. I feel like someone is asking me, "Are Chevys fast?". Uh, well......yes........and no.

As far as a I know, aspherical elements are present in many, MANY lenses. It's not a specific "type" or "brand" of lens. To my knowledge, the "aspherical" part is simply the shape and creation of one of the glass elements within the lens.

Well, i'm seeing quite a few lenses with this specific shape being sold specifically as aspherical lenses, some of them even have the word "aspherical" on the side of the lens.

Sorry for being a beginner. And i'm sorry for the photo, i just did a google search and picked a lens that looked similar.

09-02-2010, 08:16 PM   #9
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Aspherical lenses combine characteristics that otherwise require multiple spherical elements. Benefits are less light loss for more light throughput (faster f/#), i.e. a smaller lens element for lower weight, and cost savings.
09-02-2010, 08:28 PM   #10
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QuoteOriginally posted by Silverkarn Quote
Well, i'm seeing quite a few lenses with this specific shape being sold specifically as aspherical lenses, some of them even have the word "aspherical" on the side of the lens.

Sorry for being a beginner. And i'm sorry for the photo, i just did a google search and picked a lens that looked similar.
I, too, am a beginner. I'm just saying that, as far as my understanding is concerned, the "aspherical" portion of the name refers to it containing a specific type of element, which, like rhodopsin state, have their benefits.
09-02-2010, 08:30 PM   #11
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As others have mentioned, saying that's an "aspherical" lens is not saying anything - tons of lenses have aspherical elements in them. I am not sure what you thin is so unique about that particular lenses. It's a very ordinary zoom lens - optically well below average by most accounts, and not unusually small at all. I think the fact that it's so *fat* is fooling you into thinking it's shorter than it is. But it's actually quite a bit larger than the 18-55 or 50-200, and weighs as much as the first two of those put together. It's heavier and a lot fatter than the 55-300 as well. And it's even bigger and heavier than than the DA18-250 - remarkable given the latter is both wider and longer (in terms of focal lengths).

As a lens with a fairly large zoom range (28-200 is a factor of 7X), this lens might be considered a "superzoom", but it's a pretty early generation of superzooms, and as I mentioned, optically, it has a pretty poor reputation. Any of the modern superzooms would be better optically, and more importantly, the modern ones tend to go down to 18 instead of just 28. A 28-200 isn't really all that "super" on a DSLR, since 28 is just "normal" it isn't wide angle at all. So it really doesn't serve as an "all-in-one" lens nearly particularly well - kind of defeating the purpose of getting such an optically compromised and relatively large/heavy (by consumer standards) lens.

BTW, I also have no idea what you mean about the lens extending to zoom instead of moving a slide back and forth. As far as I know, this lens zooms *exactly* like just every other zoom lens made for the last couple of decade - you turn the zoom ring. And like most of those lens, the lens presumably gets physically longer as you zoom to longer focal lengths. I'm not sure what you think is unique about this lens in that respect.
09-02-2010, 08:53 PM   #12
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QuoteOriginally posted by Marc Sabatella Quote
As others have mentioned, saying that's an "aspherical" lens is not saying anything - tons of lenses have aspherical elements in them. I am not sure what you thin is so unique about that particular lenses. It's a very ordinary zoom lens - optically well below average by most accounts, and not unusually small at all. I think the fact that it's so *fat* is fooling you into thinking it's shorter than it is. But it's actually quite a bit larger than the 18-55 or 50-200, and weighs as much as the first two of those put together. It's heavier and a lot fatter than the 55-300 as well. And it's even bigger and heavier than than the DA18-250 - remarkable given the latter is both wider and longer (in terms of focal lengths).

As a lens with a fairly large zoom range (28-200 is a factor of 7X), this lens might be considered a "superzoom", but it's a pretty early generation of superzooms, and as I mentioned, optically, it has a pretty poor reputation. Any of the modern superzooms would be better optically, and more importantly, the modern ones tend to go down to 18 instead of just 28. A 28-200 isn't really all that "super" on a DSLR, since 28 is just "normal" it isn't wide angle at all. So it really doesn't serve as an "all-in-one" lens nearly particularly well - kind of defeating the purpose of getting such an optically compromised and relatively large/heavy (by consumer standards) lens.

BTW, I also have no idea what you mean about the lens extending to zoom instead of moving a slide back and forth. As far as I know, this lens zooms *exactly* like just every other zoom lens made for the last couple of decade - you turn the zoom ring. And like most of those lens, the lens presumably gets physically longer as you zoom to longer focal lengths. I'm not sure what you think is unique about this lens in that respect.
the ONLY zoom lenses i have experience with at all are long lenses where you have to move the barrel back and forth to zoom. You know, stuff made before the last couple decades.

I suppose i should have stated my knowledge base before.
09-02-2010, 08:59 PM   #13
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That certainly explains that :-).

I was assuming your were thinking about a DSLR, but if you're thinking of using this on a film camera, then most of the recent lenses I referred to are out of the question - they are designed for APS-C. So the 28-200 and a couple of third party alternatives would be it if you're in the market for a superzoom - but it will come with the same compromises I alluded to.
09-02-2010, 09:23 PM   #14
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QuoteOriginally posted by Silverkarn Quote
the ONLY zoom lenses i have experience with at all are long lenses where you have to move the barrel back and forth to zoom.
.
"Push-pull" or "one-touch" is the term for that type of zoom operation. Push-pull to zoom, twist to focus using the same ring.
09-02-2010, 09:41 PM   #15
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QuoteOriginally posted by Silverkarn Quote
Well, i'm seeing quite a few lenses with this specific shape being sold specifically as aspherical lenses, some of them even have the word "aspherical" on the side of the lens.

Sorry for being a beginner. And i'm sorry for the photo, i just did a google search and picked a lens that looked similar.
Aspherical lens elements are relatively new in cameras. They date to the '70s. They were initially HAND ground and polished. This added substantially to the cost of the lens. It was extraordinary at the time. Canon's famous 55mm F1.2 AL lens was the first. It is still an incredible lens. Then the term "Aspherical" on a lens was something special.

They are much easier to produce now. Perhaps the moniker "Aspherical" is still used to infer something special. Maybe something like the word "Color" on the TV ads in the newspaper. Now every TV at the electronics store is "Color". You have not been able to buy a large B&W TV for years.

Read this article to learn more:
canon.com/camera-museum/camera/lens/fd/data/50-85/fd_55_12_al.html

Last edited by lmd91343; 09-02-2010 at 09:46 PM.
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