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Thread: Newbie here

  1. #21

    Default Re: Newbie here

    Quote Originally Posted by zac08 View Post
    You can't get fulll f2.8 at macro distances...

    With the Nikon bodies, the camera automatically detects when the lens is much further than the original 90mm and this length ratio to the aperture size causes the aperture value to drop from f2.8 to as low as f5.6 (if I'm not mistaken, dun have the lens with me right now to do test, will add on later when I'm at home to do a test with the lens.)

    The aperture value is the ratio of the lens diameter to the focal length, and as the macro lenses often protrudes much further out when focusing at close range, this causes the aperture value to drop to a smaller one.

    As for other cameras, they may not reflect the correct aperture value even at macro distances.

    Do a check, focus at infinity, then adjust the aperture down to f2.8. Then focus closer using manual focusing, look at the aperture value change as you focus closer...

    thank you very much..yeah u r correct...... the aperture change everytime i change focus using manual & auto...so it means i can set f2.8 aperture if only the lens focus is at minimum...then it varies when the focus change also ,even my settings is aperture priority....does it mean i cant set the apperture permanently? what is the function of the apperture ring on the tamron lens? sorry many questions..anyway thanks again...

  2. #22
    Senior Member zac08's Avatar
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    Default Re: Newbie here

    Quote Originally Posted by Curapica View Post
    thank you very much..yeah u r correct...... the aperture change everytime i change focus using manual & auto...so it means i can set f2.8 aperture if only the lens focus is at minimum...then it varies when the focus change also ,even my settings is aperture priority....does it mean i cant set the apperture permanently? what is the function of the apperture ring on the tamron lens? sorry many questions..anyway thanks again...
    Yes, f2.8 is only applicable at infinity to 1.5m.
    f3.2 from 1.6 to 0.65m
    f3.3 from 0.6 to 0.55m
    and so on....

    This lens will give you full range of apertures from f2.8 down to f32 only when used focused at infinity to 1.5m. When you focus closer than 1.5m, the aperture value will be corrected to reveal the correct aperture size according to the lens focal length as it protrudes further, but this value will remain when you focus back out above 1.5m.

    As for the aperture ring, it's meant to be used on older cameras which may not have any control of aperture on the camera (i.e. F90, FMs, etc...)
    Michael Lim
    My Flickr Site

  3. #23

    Default Re: Newbie here

    Quote Originally Posted by zac08 View Post

    As for other cameras, they may not reflect the correct aperture value even at macro distances.

    Do a check, focus at infinity, then adjust the aperture down to f2.8. Then focus closer using manual focusing, look at the aperture value change as you focus closer...
    Just because Nikon doesn't let you use f/2.8 throughout the range doesn't mean other cameras "may not reflect the correct aperture value".

    I tried your "check", and my cam stayed at f/2.8 throughout. And the DOF certainly was reflective of f/2.8.
    Alpha

  4. #24

    Default Re: Newbie here

    Might just be specific to the lenses designed for Nikon
    Alpha

  5. #25
    Senior Member Galdor's Avatar
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    Default Re: Newbie here

    Quote Originally Posted by Rashkae View Post
    Just because Nikon doesn't let you use f/2.8 throughout the range doesn't mean other cameras "may not reflect the correct aperture value".

    I tried your "check", and my cam stayed at f/2.8 throughout. And the DOF certainly was reflective of f/2.8.
    Same for mine. Stayed at f2.8 throughout. No problem with that lens at all.
    Minolta. Konica Minolta. Sony

  6. #26
    Senior Member zac08's Avatar
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    Default Re: Newbie here

    Guys, does your lens protrude out when focusing at closer range??

    IF it does, then the ratio of the lens diameter will change in relation to the lens length. This WILL change the aperture. This is also the same reason why zoom lenses with variable apertures has this issue. Think about it.

    Those with fixed apertures throughout the zoom range will open up the aperture as the zoom focal length increases.
    Michael Lim
    My Flickr Site

  7. #27

    Default Re: Newbie here

    Quote Originally Posted by zac08 View Post
    Guys, does your lens protrude out when focusing at closer range??

    IF it does, then the ratio of the lens diameter will change in relation to the lens length. This WILL change the aperture. This is also the same reason why zoom lenses with variable apertures has this issue. Think about it.

    Those with fixed apertures throughout the zoom range will open up the aperture as the zoom focal length increases.

    thank you zac08 & thank you to other guys also for sharing ur knowledge that exactly what happens to my camera with tamron lens...the aperture varies on focal distance.....i just thought that i can fixed the aperture settings if i am in aperture priority even on different focal distance..

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