Difference between 18-70mm and 18-250mm lens, apart from the obvious?

Discussion in 'Digital Photography' started by iSamurai, Aug 1, 2009.

  1. iSamurai macrumors 65816

    iSamurai

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    #1
    I'm wondering what's the difference between a standard lens and a lens that can zoom from close to far...

    But let's not discuss the obvious: zoom, price, weight.

    Is there any picture quality difference between the lenses? Will the 18-250mm lens have slightly "dark edges" and straight lines distorted (like bulbing/curving) when not zoomed afar?
     
  2. gatepc macrumors 6502

    gatepc

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    #2
    It depends on the lens's, in general the more focal range a lens covers the more likely it is to have lower IQ and so forth.
     
  3. HBOC macrumors 68020

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    #3
    well, apertures will vary as well, at the same focal length. Let's say the said 18-70mm is a 2.8 fixed through the whole range, and the 18-250 is probably atleast a 3.5-5.6, which varies through different focal lengths.
     
  4. clams macrumors member

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    #4
    One thing about all-around zooms like the 18-250mm is the fact that it is not completely sharp throughout the entire range. This is because it is very difficult to design a lens to be able to adapt to so many different focal lengths and remain sharp. Usually this problem would occur at the highest focal lengths of the lens.
     
  5. HBOC macrumors 68020

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    #5

    well, this is true generally of consumer grade lenses. Most manufacturers' offer higher end glass (Canon L) that will have close to the same focal range, that will be much sharper than their consumer grade counterparts..
     
  6. cube macrumors G5

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    #6
    Just for the record, there is no 18-70 or whereabouts fixed f/2.8
     
  7. HBOC macrumors 68020

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    #7
    Well, I know that is not a focal length in Canons' lineup. It sounds like a Nikon or something... I know that Canon makes a 17-55 2.8 and a 24-70 2.8.

    Lets just say that the 18-70 is 3.5-5.6 and the 18-200 (whatever the other example was) is f3.5-6.3 (most likely would be f3.5-5.6) At the same focal length on both lenses, I am assuming that the longer zoom would be a bit slower wide open.

    Currently, i dont really have any lenses that overlap focal lengths to test this with. i have an 18-55 and a 55-250.. in this case, the 55-250 is faster wide open than the 18-55..
     
  8. cube macrumors G5

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    #8
    Those canon lenses are not whereabouts of a 18-70. A 17-70 would be, as well as a 16-85 (but not the reverse).

    It's more likely that a 18-200 will end in 6.3. Only Nikon and Canon offer 5.6

    If you compare 18-70 and a 18-200 both f3.5-5.6, there's a good chance the 18-200 will be faster at 70mm.
     
  9. clams macrumors member

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    #9
    Definitely true. But if you look carefully. I don't think there are any Ls that cover a focal range as wide as 18-250mm. For good reason too.
     
  10. HBOC macrumors 68020

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    #10
    they make a 28-300L, but that is the widest they have (to my knowledge) with this much variation in focal length..
     
  11. clams macrumors member

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    #11
    Oh true. I forgot about that one. I hear good things about it. Then again, it is a solid 3.7lbs of glass
     
  12. El Cabong macrumors 6502a

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    #12
    Listing brands, at the very least the brand of your camera, is useful.

    In any case, here are links to some reviews that pick out the less-than-obvious features of 18-70 and 18-250mm lenses:

    Nikon 18-70mm
    Photozone
    SLRGear

    Sony 18-70mm
    DPReview
    Photozone
    SLRGear

    Tamron 18-250mm
    Photozone
    SLRGear

    Sigma 18-250mm
    SLRGear

    In a nutshell, the Nikkor is a solid performer, the Sony is not (corner softness and high CA throughout range), the Tamron superzoom is surprisingly good considering its range but still has the limits of a superzoom, and the Sigma's sharpness suffers significantly in its telephoto focal lengths.

    Compared to the Nikkor (not so much the Sony, though it's still better optically than the superzooms), you'll compromise focus speed and max aperture (i.e. max at 70mm on the Nikkor is f/4.5 whereas it's about f/5 for the others) when using the superzooms, not to mention optical quality (sharpness, CAs, distortion, etc). Also, the superzooms are prone to lens creep.

    In general, the superzooms trade off optical quality and aperture for their wide range, although there isn't a *huge* difference in quality until you compare them to primes or f/2.8 lenses.

    Note that Canon does not make lenses in these specific ranges.
     

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