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Thread: Needs explanation on 'magnification'

  1. #1
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    Default Needs explanation on 'magnification'

    Dear Gurus,

    I am doing research on Canon 70-200mm 2.8L and 70-300mm 4-5.6L lens and deciding which is a better and more useful lens for me. Although common sense tells me that 70-300 could give me a better zoom range, the max magnification of the lens according to the canon lens app are both the same - 0.21(at 200mm) and 0.21(at 300mm) respectively. This is very puzzling to me. Does that mean both lens get the same zoom range, i.e. 300mm doesnt allow me to have a greater zoom?

    Enlightenment greatly appreciated.

  2. #2

    Default Re: Needs explaination on 'magnification'

    the maximum magnification that you're referring to here isn't the zoom range. it is the max magnification you can achieve with close-up subjects due to each lens' minimum focus distance (at 200mm and 300mm on each lens). the 70-300mm will give you 'more zoom' for sure
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    Default Re: Needs explaination on 'magnification'

    Focal length affects field of view, the area of the real life situation that will be in the frame. Higher focal length will give smaller field of view, vulgo: zoom.
    Magnification is the ratio between real life size of an object and the size of it on the sensor / film. Check the definition of magnification as explained in the sticky threads in macro section. Magnification is affected by focal length and minimum focus distance. If you have a longer focal length but need to be further away it cancels off each other. That's why you get the same result. But the 300mm are maybe more helpful in other situations..? That's your call.
    EOS

  4. #4

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    In simpler terms (hopefully), magnification refers to how big a subject is in the image. To make a subject big, you need to photograph it as close as possible, at the lens' MFD.

    If the two lenses give same magnification, means the 300mm lens has a mfd that is 50% further than the 200mm lens..
    hi

  5. #5

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    Quote Originally Posted by silvermoon1407 View Post
    In simpler terms (hopefully), magnification refers to how big a subject is in the image. To make a subject big, you need to photograph it as close as possible, at the lens' MFD.

    If the two lenses give same magnification, means the 300mm lens has a mfd that is 50% further than the 200mm lens..
    Just so that TS knows, MFD stands for minimum focusing distance.

    The 300mm is a longer / further minimum focusing distance than the 200mm. Hence, even though the focal length is longer, the 300mm still needs to maintain a greater distance over the subject than the 200mm lens, resulting in the same magnification.
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    Default Re: Needs explaination on 'magnification'

    Thank you for the replies. Does clear up a little of my misconception.

    However, I went back to check the min focusing distance, for both lenses are the same -- 1.2m/3.9ft. Am I missing something else here?

  7. #7

    Default Re: Needs explaination on 'magnification'

    Quote Originally Posted by mouserene View Post
    Thank you for the replies. Does clear up a little of my misconception.

    However, I went back to check the min focusing distance, for both lenses are the same -- 1.2m/3.9ft. Am I missing something else here?
    You are not missing anything. MFD works at the widest end, and both are 70mm.

  8. #8

    Default Re: Needs explaination on 'magnification'

    Quote Originally Posted by mouserene View Post
    Thank you for the replies. Does clear up a little of my misconception.

    However, I went back to check the min focusing distance, for both lenses are the same -- 1.2m/3.9ft. Am I missing something else here?
    i found that a bit strange too. just read this from The-Digital-Picture.com review of the 70-300L:

    "If you look closely at these numbers, it becomes obvious that something interesting is going on with a 300mm lens and a 200mm lens having the same MFD (Minimum Focus Distance) AND the same MM (Maximum Magnification). The primary reason for this is that the 70-300 L has a rear focusing design that results in a shortened focal length at close focus distances.

    Testing shows that my 70-300 L IS will focus as close as 40.91” and 43.82” (1039mm and 1113mm) at 70mm and 300mm respectively and that the actual maximum magnification is indeed slightly higher than that of the Canon EF 70-200mm f/2.8 L IS II USM Lens. That the 70-300 L will manually focus slightly closer than it will autofocus is likely why I am seeing better results than specified."

    Check out the review itself if you want to read more on it, but that's the essential bit that i found. This is indeed a bit of a strange case. Usually if a 70-200mm and 70-300mm lens have the same MFD throughout their focal range (like these two do), the 300mm one will have greater max magnification. Hope this helps without confusing more!
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    Default Re: Needs explaination on 'magnification'

    Quote Originally Posted by heshanj View Post
    i found that a bit strange too. just read this from The-Digital-Picture.com review of the 70-300L:

    "If you look closely at these numbers, it becomes obvious that something interesting is going on with a 300mm lens and a 200mm lens having the same MFD (Minimum Focus Distance) AND the same MM (Maximum Magnification). The primary reason for this is that the 70-300 L has a rear focusing design that results in a shortened focal length at close focus distances.

    Testing shows that my 70-300 L IS will focus as close as 40.91 and 43.82 (1039mm and 1113mm) at 70mm and 300mm respectively and that the actual maximum magnification is indeed slightly higher than that of the Canon EF 70-200mm f/2.8 L IS II USM Lens. That the 70-300 L will manually focus slightly closer than it will autofocus is likely why I am seeing better results than specified."

    Check out the review itself if you want to read more on it, but that's the essential bit that i found. This is indeed a bit of a strange case. Usually if a 70-200mm and 70-300mm lens have the same MFD throughout their focal range (like these two do), the 300mm one will have greater max magnification. Hope this helps without confusing more!
    Thank you very much! Now I am a little more enlightened.

  10. #10

    Default Re: Needs explaination on 'magnification'

    I am too! Cheers
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