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Thread: Qn about prime lens and crop factor

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    Default Qn about prime lens and crop factor

    Been reading a few books about photography and they recommend practicing with a prime lens (50mm) before buying any other lens. However, with a 1.5 crop factor on my DSLR, a 50mm prime lens is going to become 75mm equivalent. Does that mean that I need to get a 35mm or 28mm wide angle to be my prime lens? Would that introduce distortion?

    So which is better? Use the 50mm or the 35mm as the prime lens?
    Last edited by red_ryder; 14th March 2005 at 09:57 AM.

  2. #2
    Moderator ortega's Avatar
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    get the 50mm, more useful later

    I think that the reason that the books recommend using a prime lens (Fixed focal lenght) to practice is to get you to walk instead of zooming.

    The charecteristics of the lens is still the same, only the FOV is changed.

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    choose the lens which will give u the final effective focal length

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    A 50mm lens on a crop factor body will still look like a 50mm lens except having its sides chopped off. Same thing as what ortega said... only the FOV changes. Lens characteristics is the same.

    Also 50mm is a cheap and fast lens to start you out. Gives you room to play with aperture ranges and approximates a human's eye perspective.

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    Moderator Cactus jACK's Avatar
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    Quote Originally Posted by red_ryder
    Been reading a few books about photography and they recommend practicing with a prime lens (50mm) before buying any other lens. However, with a 1.5 crop factor on my DSLR, a 50mm prime lens is going to become 75mm equivalent. Does that mean that I need to get a 35mm or 28mm wide angle to be my prime lens? Would that introduce distortion?

    So which is better? Use the 50mm or the 35mm as the prime lens?
    red - you're right to say that 50mm would effectively look like 75mm, and therefore in order to get the FOV a 50mm lens would have on a film camera, you would need 35mm lens on a DSLR. distortion? not with these 2 lenses, i think that you would only start seeing distortion when you're down at the 20mm / 24mm range.

    however, as to answering your question on which is better? like what some of the others were saying, they really do serve different purposes, but they are both sharp and with great colour and contrast. but interms of cost, the 50f1.8d is only about $175 whereas the 35f2d goes for $490 (if you can get your hands on one of this one).

  6. #6

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    Quote Originally Posted by red_ryder
    Been reading a few books about photography and they recommend practicing with a prime lens (50mm) before buying any other lens. However, with a 1.5 crop factor on my DSLR, a 50mm prime lens is going to become 75mm equivalent. Does that mean that I need to get a 35mm or 28mm wide angle to be my prime lens? Would that introduce distortion?

    So which is better? Use the 50mm or the 35mm as the prime lens?
    Yes, if you are trying to follow what the books recommend. The 35mm or 28mm prime is the lens to practice on at the beginning - if you are holding a 1.5crop body, not the 50mm. .

    Distortion introduction - this depends on the lens characterisitics. Each lens will have its own. Some 35mm/wider lens may even have has less distortion than the 50mm.
    There are some very strong advantages in learning this way - you learn fast to optimise the use of prime, frame with your legs, compose way in advance, and there is no need to contend with the varying performance of a zoom as the focal length varies etc.

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