What dz it mean when it says "Lens is 'equivalent to...' in the zoom range?

Discussion in 'Photography Beginners' Forum' started by ottor, Jun 10, 2009.

  1. ottor

    ottor No longer a newbie, moving up!

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    Interested in the Tamron 18-270mm - it states that it's "Equivalent" to a 28-419mm... I have your standard kit Canon 75-300 - will this 270mm lens get closer than my 300mm ?? :confused::confused::confused: I think it's referring to a 35mm lens, but what do they mean? - How will a person know that, in this case and others, a 270mm will get closer than a 300mm ???
     
  2. adamwilliamking

    adamwilliamking TPF Noob!

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    no your 300 is actually 112 - 450

    its the crop factor of a full frame (or 35 mm equivelant) up against your crop sensor.
    Anything you read in mm should be times'd by 1.5,1.6 depending on your camera.
    Even if it is a lens MADE for crop sensor.
     
  3. bigtwinky

    bigtwinky No longer a newbie, moving up!

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    Its based on the type of camera you have.

    All lenses are listed with a focal lenght as it would be on a 35mm camera - known in the digital world as full frame...the higher end cameras.

    Cameras like the Canon Rebel, 50D, Nikon D40, D90 and such have a smaller sensor than the full frame cameras. These are referred to as crop cameras or APS-C. Canons have a crop factor of x1.6 and Nikons of x1.5

    So if you are looking at a Canon 70-300mm f/4.5-5.6 lens, that is the correct focal lenght for a full frame camera. If you have a crop sensor camera, then you have to multiply each mm value by 1.6 (as its Canon) to get the effective focal range
    70x1.6 = 112
    300x1.6 = 480

    So the effective focal range of a 70-300 on a Canon crop sensor is 112-480
     
  4. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Take note that this is a comparison factor for the field of view only...the actual focal length of a lens is exactly what is says on the lens...it does not change.
    But because the sensor is smaller than a frame of 35mm film, the image is cropped from what we might expect from that lens (when used on a 35mm film SLR).
    That's the key part that people often forget. This is only a comparison to what people expect from 'full frame (35mm film) because that is the standard they have chosen to use. If you don't have any preconceived notions of the view that a certain focal length with give you...then all of this should be ignored.

    Look through the viewfinder. What you see is what you get (although most of these cameras only give you something like 95% coverage).
    [​IMG]


    No.
     
  5. KmH

    KmH Helping photographers learn to fish Supporting Member

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    To clarify slightly what Mike said. Most of the viewfinders only show 95% of what will be eventually be the actual image.

    And to clarify a previous statement. Full frame sensored cameras (full 35mm sensor) have no crop factor, only the camera's with the smaller APS-C sized sensors. Nikons have a 1.5 crop factor and Canon's have a 1.6 crop factor. Some other brands have sensors with a different aspect ratios and thus differing crop factors.
     
  6. adamwilliamking

    adamwilliamking TPF Noob!

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    sorry i missed a world, meant to say "crop factor of a full frame LENS ... ... on a crop sensor.
     
  7. inTempus

    inTempus TPF Noob!

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    Just to add to the confusion, there's also APS-H format (1.3) which is offered by Canon.

    There's also the "four thirds" system offered by Olympus and the Foveon system offered by Sigma.

    :D
     
  8. ottor

    ottor No longer a newbie, moving up!

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    And I thought "Snapping pretty pictures" was gonna' be easy..... :D
     
  9. bigtwinky

    bigtwinky No longer a newbie, moving up!

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    hehe, the technical part is the easiest and usually the first hurdle people overcome.

    Learning what means what, where to look, what to buy and what to use in certain situations.

    The next is actually learning lighting, composition, people management, posing and so on.

    Lots of stuff to learn, but its well worth it if you enjoy what you are doing.
    And the great part? There is always something new to try out.
     
  10. Henry Peach

    Henry Peach TPF Noob!

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    Big Mike's got it right. People often say crop factor/format effects focal length, but it doesn't. Decreasing format size does not increase magnification. A 200mm has the same magnification on whatever camera from APS-C to 4x5. If you use the lens on an APS-C DSLR and a 35mm DSLR, and then enlarge the photos the same enlargement ratio (enlarge both by x10 for instance), the subject will be exactly the same size, although the prints won't be the same size.
     
  11. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Everything would be a lot easier if we had never heard of 'The Crop Factor'.
    Just put it out of your mind and concentrate on snapping those pretty pictures. :)
     

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