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Thread: Lens Talks

  1. #1
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    Default Lens Talks

    Hi there,

    Having notice the lens with attributes like f3.5-5.6, or f4-XX and etc...

    The price could be so much different if f2.8 and smaller...

    Anyone can enlighten me on this?

  2. #2
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    Default Re: Lens Talks

    coz smaller f number need larger lens elements and they cost more. If you are talking about fixed aperture lens like the 70-200/2.8, they can maintain that aperture throughout the range instead of going from f3.5 to f5.6 as you zoom out.

  3. #3
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    Default Re: Lens Talks

    But the price different can be 4 to 5 times that the normal lens!

    But anyway thanks for answering...

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    Moderator ortega's Avatar
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    Default Re: Lens Talks

    harder to make mah
    and also usually the constant f-stop F2.8 is professional grade lens

  5. #5

    Default Re: Lens Talks

    act its coz at 2.8, the relative size of the aperture is alot larger than say at 3.5 or above.... thus it lets in more light, and allows u to use the lens at a higher shutter speed (but wider aperture) in dim light conditions....

    that's y 2.8 lenses (especially the constant ones) are in such high demand...esp for telezooms... with a longer focal lenght..if u stick by the 1/focal lenght rule for shutter speed, a wider aperture will help u achieve the faster shutter speed....

    cheers...

  6. #6
    Senior Member Canew's Avatar
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    Default Re: Lens Talks

    Quote Originally Posted by Witness
    the 1/focal lenght rule for shutter speed, a wider aperture will help u achieve the faster shutter speed....

    cheers...
    For the 1/focal lenght rule for shutter speed of telezooms, do we need to take the FOV multiplier into consideration? For example on a 1.6X FOV camera, will we need to set the shutter speed to 1/320 sec. or the usual 1/200 sec. when we are shooting using a 200 mm lens?

    Thanks.

  7. #7

    Default Re: Lens Talks

    Quote Originally Posted by Canew
    For the 1/focal lenght rule for shutter speed of telezooms, do we need to take the FOV multiplier into consideration? For example on a 1.6X FOV camera, will we need to set the shutter speed to 1/320 sec. or the usual 1/200 sec. when we are shooting using a 200 mm lens?

    Thanks.
    that rule is just a rough guide

    use whatever shutter speed u can manage

  8. #8

    Default Re: Lens Talks

    Quote Originally Posted by erizai
    But the price different can be 4 to 5 times that the normal lens!

    But anyway thanks for answering...
    at the telephoto end of that lens a f2.8 aperture instead of a f5.6 implies 2 f stops which translates into 4 times the amount of light ~ 4 times the cost

  9. #9
    Senior Member Canew's Avatar
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    Default Re: Lens Talks

    Quote Originally Posted by user111
    that rule is just a rough guide

    use whatever shutter speed u can manage
    Thanks, user111.

  10. #10

    Default Re: Lens Talks

    Quote Originally Posted by Witness
    act its coz at 2.8, the relative size of the aperture is alot larger than say at 3.5 or above.... thus it lets in more light, and allows u to use the lens at a higher shutter speed (but wider aperture) in dim light conditions....

    that's y 2.8 lenses (especially the constant ones) are in such high demand...esp for telezooms... with a longer focal lenght..if u stick by the 1/focal lenght rule for shutter speed, a wider aperture will help u achieve the faster shutter speed....

    cheers...
    Add on to this, for a bigger aperture (smaller F stop). The lens can focus faster. Because lens are focus wide open and stop down during shutter release.

  11. #11

    Default Re: Lens Talks

    Quote Originally Posted by Canew
    For the 1/focal lenght rule for shutter speed of telezooms, do we need to take the FOV multiplier into consideration? For example on a 1.6X FOV camera, will we need to set the shutter speed to 1/320 sec. or the usual 1/200 sec. when we are shooting using a 200 mm lens?

    Thanks.
    honestly this is debatable.... but if we take the censor size as a guide to the "real focal length" then i guess yes.... but i erhm dun follow this rule and still get great results hahaha

    cheers..

  12. #12
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    Default Re: Lens Talks

    Quote Originally Posted by Canew
    For the 1/focal lenght rule for shutter speed of telezooms, do we need to take the FOV multiplier into consideration? For example on a 1.6X FOV camera, will we need to set the shutter speed to 1/320 sec. or the usual 1/200 sec. when we are shooting using a 200 mm lens?

    Thanks.
    I think no need to take 1.6X multiplier into account. Just shoot at 1/200 sec will do...cos you're still shooting at 200mm...

    It's just that the sensor is smaller, cropping the image to a smaller field of view.

  13. #13
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    Default Re: Lens Talks

    Quote Originally Posted by tincup
    I think no need to take 1.6X multiplier into account. Just shoot at 1/200 sec will do...cos you're still shooting at 200mm...

    It's just that the sensor is smaller, cropping the image to a smaller field of view.
    as the image is cropped, so is the blur due to camera shake. steady hands with tripod and/or VR/IS/OS will give blur-free images most of the time. with my 70-200vr@200mm, i can handhold @1/20sec. of course VR/IS/OS lenses are considerably more expensive

  14. #14
    Senior Member Canew's Avatar
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    Default Re: Lens Talks

    Thanks everyone, for all the comments.

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