simple lens Q ?

Discussion in 'Photography Beginners' Forum' started by minister, Jul 21, 2010.

  1. minister

    minister TPF Noob!

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    Hi,

    as I am noob I have right to ask silly question

    hear I goes - I have 18-55 kit lens
    as far as i understand I can shoot 18mm wide shot and 55mm narrow shot

    my confusion is if I wanted to shoot a wide angel , why to buy those small focal length when I already have 18mm wide available ,

    and why those small number wide angel lens say 24mm so expensive because the aperture they provide, my best guess !!!

    my simple question is what would i achieve with those small focal length lens what i can't get with my 18-55 mm :meh:
     
  2. oldmacman

    oldmacman TPF Noob!

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    If you are using an 18-55, I'm going to assume you have a crop sensor, APS-C, sized sensor. This means to determine your actual focal length, you multiply the number by its crop factor (1.6) for APS-C. So your 18mm end is really a 29mm, more or less.

    The same would go for the 24mm.

    Yes, the aperture is part of the reason the lens will be more expensive, but there are other factors like:
    - improved optics
    - build quality
    - flare control
    - sharpness

    Until you get really good at photography,or you need to make larger prints, your kit lens should serve you well.
     
  3. Dao

    Dao No longer a newbie, moving up!

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    Because they are different. Different in build quality, optical quality as well as other performance factors.

    A lens usually cost more when ...

    - It is well build and solid. Some of them even have weather seal.
    - It has great optics so that the final image is sharp and less optical issue such as distortion or CA.
    - It has build in image stabilizer.
    - It has fast quiet autofocus motor.
    - It has a large max. aperture.

    So in your case, I believe the 24mm lens most likely is a faster lens (larger max. aperture), better build and optically better than your stock kit lens. And therefore cost more.
     
  4. rusty9

    rusty9 TPF Noob!

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    well, it provides a larger aperture (which is more expensive) so it performs better in low light. the lenses you mentioned have better build quality, too. and those lenses have less zoom range. the more zoom it has the less quality. so that is why primes are better than zooms.
     
  5. rusty9

    rusty9 TPF Noob!

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    dang it. you two beat me to it.
     
  6. TiCoyote

    TiCoyote TPF Noob!

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    All of those factors are correct (build quality, optics, aperture, etc.). Also, wide-angle lens is a bit of a different animal. The lens is round, so it wants to produce a round image. However, the sensor is rectangular, so the image needs to be focused in a way that's rectangular. Refocusing a round image in a rectangular format is tricky, and therefore expensive. If you just let the image focus so that it was round, you would have a distorted image. A fisheye lens allows it to focus a round image. Essentially, a fisheye is a wide angle lens that does not produce a rectangular image. You will notice there are quite a few inexpensive fisheye lenses for this reason (amongst others).
     
  7. Robin Usagani

    Robin Usagani Been spending a lot of time on here!

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    Minister, if you really want the "wide angle" feel on your camera, you have to by 10mm or 12mm because your sensor is cropped. The expensive fast wide angle lens are really meant for a full sensor. If you buy that expensive lens and use it on your camera, it will be a like a fast zoom lens.
     
  8. Dao

    Dao No longer a newbie, moving up!

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    :scratch:
     
  9. minister

    minister TPF Noob!

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    I had this Q also in my mind you just cleared
     
  10. minister

    minister TPF Noob!

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    I am very thankful you all are so help full to clear my doubts
     
  11. Robin Usagani

    Robin Usagani Been spending a lot of time on here!

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    what? PUt a 24mm on a crop sensor, what will that do?
     
  12. Dao

    Dao No longer a newbie, moving up!

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    But it will not change into a zoom lens though.
     

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