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This question already has an answer here:

Are there some disadvantages of a zoom-lens with wide range focal length compare to a lens with narrow range both having the same max. aperture?

For example, if we have two lenses:

  1. Sigma 18-55mm f4
  2. Sigma 18-300mm f4

Does the second lens have some advantages, except zoom, of course? I mean when producers of camera lenses try to stow a wide range of focal length in one lens, does it affect the quality?

marked as duplicate by mattdm, Dan Wolfgang, Community Aug 31 '15 at 17:46

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • We have a number of other very similar questions in the superzoom tag, too. – mattdm Aug 31 '15 at 16:12
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Absolutely, there is a drop in quality as the zoom-ratio increases. This is normal because the designers have to made compromises when placing lens elements. This gives a performance which is uneven too. Many times you can have decent sharpness at one end of the zoom and it will truly terrible at the other end or somewhere in the middle.

The other thing is that ultra-zoom lenses are designed to be relatively small, even compred to a long lens with a similar reach. For example, there is no 18-300mm F/4. A 300mm F/4 exists and it is quite large, so the Sigma 18-300mm is F3.5-6.3 which means it is extremely dim at the telephoto end. That means much less light which reduces your ability to shoot as light diminishes. The 18-300mm weighs less than 600g while a 300mm F/2.8 weighs 2.4kg even though it does not zoom at all! It lets a lot of light in though and is optimized to produce top-notch quality at 300mm.

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