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Thread: why we shoot with primes

  1. #1
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    why we shoot with primes

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    Here's the same ketapang tree, shot first with a Canon EF 28-135mm zoom lens, and then a Canon EF 100mm Macro prime lens. Shots are taken a minute apart (as fast as I can change lenses ) at f=100mm, 1/125s and f/8 aperture (the typical sweet spot).

    the original shot, the distance is quite far so I assume both lens would focus at infinity, anyway both are using AF on a 20d.




    unresized crop, first the EF28-135mm zoom then the EF100mm Macro prime


    Last edited by hwchoy; 11th Feb 2006 at 21:44.
    why I don't do garden hybrids and aquarium strains: natural species is a history of Nature, while hybrids are just the whims of Man.
    hexazona crumenatum Galleria Botanica

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    both are blur leh.. like taht rather manual focus..

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    at that distance! I don't think MF can make any difference.

    actually it is supposed to show that a zoom will be less sharp than a prime, usually
    Last edited by hwchoy; 12th Feb 2006 at 03:54.
    why I don't do garden hybrids and aquarium strains: natural species is a history of Nature, while hybrids are just the whims of Man.
    hexazona crumenatum Galleria Botanica

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    So choy, what exactly is a prime?

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    a prime lens is one that has a single fixed focal length, as opposed to a zoom lens which has a range of focal lengths. due to the compromises necessary to allow a lens to focus at a range of focal lengths, zooms has IN GENERAL much lower performance against prime lenses.
    why I don't do garden hybrids and aquarium strains: natural species is a history of Nature, while hybrids are just the whims of Man.
    hexazona crumenatum Galleria Botanica

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    I would assume a zoom also has more glass between the subject and the negative hence the slight blur.

    How about cost?

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    Quote Originally Posted by XnSdVd
    I would assume a zoom also has more glass between the subject and the negative hence the slight blur.

    I've never thought of that, you could check out the various lens manufacturer sites who will state the number of elements and groups for each lenses, and see if you can detect a pattern.

    However I do not think more elements causes blur, loss of light perhaps.
    why I don't do garden hybrids and aquarium strains: natural species is a history of Nature, while hybrids are just the whims of Man.
    hexazona crumenatum Galleria Botanica

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    And the cha-ching? $$$?

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    given the same grade, I would think primes cost less as they are less complex to design and make. but then you will need several primes to cover the range of a zoom.
    why I don't do garden hybrids and aquarium strains: natural species is a history of Nature, while hybrids are just the whims of Man.
    hexazona crumenatum Galleria Botanica

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    Choy,

    You should compare the Canon EF 100 mm f/2.8 Macro USM with the Canon EF 70-200 mm f/2.8 USM IS @ 100 mm. Fairer.

    Cheers,
    I have dwarf cichlids in my tanks! Do you?

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    no benny, my comparison is fair because they are both in my pouch actually why do you say that? since both 28-135 and 70-200 covers 100mm albeit at either end of their range.

    trying to MF a CZ 28-80 through the lousy 20d viewfinder is screwing my eyesight!
    why I don't do garden hybrids and aquarium strains: natural species is a history of Nature, while hybrids are just the whims of Man.
    hexazona crumenatum Galleria Botanica

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    Quote Originally Posted by hwchoy
    trying to MF a CZ 28-80 through the lousy 20d viewfinder is screwing my eyesight!
    I would recommend a full frame to solve this problem. 5D?

    As for the lens comparison, the Canon EF 100 mm f/2.8 Macro USM is know to be one of the sharpest lens that Canon has in it's stable. So is the Canon EF 70-200 mm f/2.8 L. Comparing most lenses with a marco for details is not fair, but the 70-200 might just be able to stand up to the challenge.

    Cheers,
    I have dwarf cichlids in my tanks! Do you?

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    and both lenses are F2.8, same "amount" of light entering and both are "L" therefore more fair mah.....

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    eh, the EF100mm not "L" lah, the most just L-wannabe

    but actually both shot taken at f/8 so same amount of light. at most the EF100mm AF better due to larger aperture at metering?

    btw what do you guys think of the AF performance, especially that of the EF100mm? the tree is easily 50ft high and has to be at least 100m away. I AF with the centre sensor at the top-most leafy bush.
    why I don't do garden hybrids and aquarium strains: natural species is a history of Nature, while hybrids are just the whims of Man.
    hexazona crumenatum Galleria Botanica

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    To be honest, I wouldn't really know about the Auto Focus performance as I don't recall using it. My lens is almost permanently set to manual focus.

    Cheers,
    I have dwarf cichlids in my tanks! Do you?

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    err....when i was shooting...it was manual all the way.. dont know about auto..hahaha..

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    ok, assuming the same shot is done with MF, with a proper split prism screen, can the same lens achieve a sharper image?

    very tempted to get a split prism sscreen, but afraid it will be hard to track fish in the viewfinder.
    why I don't do garden hybrids and aquarium strains: natural species is a history of Nature, while hybrids are just the whims of Man.
    hexazona crumenatum Galleria Botanica

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    Quote Originally Posted by hwchoy
    ok, assuming the same shot is done with MF, with a proper split prism screen, can the same lens achieve a sharper image?
    For this shot....No.

    For macro shots.....Yes.

    Cheers,
    I have dwarf cichlids in my tanks! Do you?

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    heehee of course lah, even my G5 can do better at macro distance
    why I don't do garden hybrids and aquarium strains: natural species is a history of Nature, while hybrids are just the whims of Man.
    hexazona crumenatum Galleria Botanica

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    Quote Originally Posted by hwchoy
    Here's the same ketapang tree, shot first with a Canon EF 28-135mm zoom lens, and then a Canon EF 100mm Macro prime lens. Shots are taken a minute apart (as fast as I can change lenses ) at f=100mm, 1/125s and f/8 aperture (the typical sweet spot).

    the original shot, the distance is quite far so I assume both lens would focus at infinity, anyway both are using AF on a 20d.
    Did you shoot both on tripod? Not sure if the weight difference can cause some shake at 1/125.

    f8 - sweet spot? I read during those EOS film days that the sweet spot is about 2 stops after the widest aperture. So the 100/2.8 is best used at f/5.6? Not sure if true nowadays...

    I agree primes should yield sharper pics normally.

    Cheers!
    koah fong
    Juggler's tanks

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