About lens


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dormy

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Nov 11, 2008
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#1
I've read stickies but Im still unsure

there are lens like
17-50mm (for wide angle)
17-70mm (for walkabout)
18-250mm (for telephoto)

does it mean 18-250mm is able to perform as a 17-50mm and 17-70mm lens also? if so why do people get different types of lens rather than a single lens with a broad range?

another question is- do I need to get a lens with auto focus?
or issit people by diffrent manual focus lens with lesser range because cheap?
if so i can just buy 18-250mm with AF right?
 

Galdor

Senior Member
Jul 5, 2006
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#2
Guess you will have to read more.

18-250mm is a great versatile lens but the IQ cannot be compared to the better lenses each camp offers.

17-50mm is a constant f2.8 lens (if you're refering to the Tamron). It's good for low light situation and the range is pretty good on an APS-C sensor.

17-70mm (I presume this lens is from Sigma), gives you a longer range but lose out in terms of max. aperture size.

So which lens to use, really depends on individual and what he wants to use the lens for.

AF or MF will depend on you too. Some people are very comfortable with MF while some are not and some of the great lenses (eg. Carl Zeiss) can only be MF on most camera, except the Sony DSLRs.

By the way, which camera are you using now?
 

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dormy

New Member
Nov 11, 2008
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#3
ty for the reply
sony a350 with the 17-70mm lens
so the larger the range, the IQ will be lower?
and people get lens with lesser range because of better IQ and better control of aperture?
 

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Rashkae

Senior Member
Nov 28, 2005
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#4
ty for the reply
sony a350 with the 17-70mm lens
Do you mean the 18-70 kit lens? It's not a bad lens at all, best to master that first before deciding if you need to buy another lens.
 

Octarine

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Staff member
Jan 3, 2008
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#5
SLR means: get the right lens for the right purpose. Using a "10-500" lens defeats the idea of changeable lenses. Secondly, a lens for such a wide range will never achieve the same image quality than a lens for a small range or even a single focal length (prime lens). It's all about physics and the design of the lens. Look at the maximum aperture and the price as well.
Check the line-up of various manufacturers and you'll notice certain common ranges that everybody has: 10-22; 17-55; 55-250 (plus/minus a few mm and some overlapping). There must be a good reason why lens manufacturer do this .. and it cannot be just marketing and direct competition.
 

giantcanopy

Senior Member
Feb 11, 2007
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#6
I've read stickies but Im still unsure

there are lens like
17-50mm (for wide angle)
17-70mm (for walkabout)
18-250mm (for telephoto)

does it mean 18-250mm is able to perform as a 17-50mm and 17-70mm lens also? if so why do people get different types of lens rather than a single lens with a broad range?

another question is- do I need to get a lens with auto focus?
or issit people by diffrent manual focus lens with lesser range because cheap?
if so i can just buy 18-250mm with AF right?
Hi Dormy

There are several online resources to read up on what consitutes a wide angle / standard / normal / telephoto lens. The lenses you mentioned are zoom lenses. For walkabout it depends on what is the focal length you are referring to, and yes the 18-250mm would be a convienient flexible zoom.

However of course the bigger the zoom ratio, the more issues with lens abberrations and other factors that may affect the image quality ( although on the whole they are definitely usable ) Different lenses made differently may have varying qualities as well.

Other varying factors includes the maximum widest aperture the lens can go.

AF is a commonplace in most of the newer lenses ( with capability of manual focusing ). While the older lenses were manual focused, some of the newer lenses are made manual focus only. Whether you can use the older cheaper manual focusing lenses will depend on whether the camera - lens mount is compatible.

Ryan
 

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PrimePhotog

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Oct 25, 2007
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#7
so the larger the range, the IQ will be lower?
Depends...But usually superzoom lenses such as the 18-200 and the 28-300 do not have excellent image quality or large max apetures.People buy them for the convenience of not having to change lenses.However,there are many lenses with a large zoom range but have top-notch image quality.ie. 70-200 f2.8 or 200-400 f4
 

Octarine

Moderator
Staff member
Jan 3, 2008
12,492
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Pasir Ris
#8
Depends...But usually superzoom lenses such as the 18-200 and the 28-300 do not have excellent image quality or large max apetures.People buy them for the convenience of not having to change lenses.However,there are many lenses with a large zoom range but have top-notch image quality.ie. 70-200 f2.8 or 200-400 f4
The zoom range of 18-200 is about 11x, the zoom range of 200-400 is 2x - not really a 'large zoom range'. This low zoom range is the key for the high quality of the lenses. But: better don't use the term 'zoom' at all, highly confusing. Important is the real focal length and the body (crop factor).
 

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