Lens Mount Question (Canon DSLR)

Discussion in 'Photography Beginners' Forum' started by iskoos, Dec 15, 2009.

  1. iskoos

    iskoos TPF Noob!

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    Hi,

    I plan on buying a Canon DSLR. I found out that 5D and Rebel series DSLR's use same lenses. In other words, they do have the same lens mount (what Canon calls "EF").
    I definitely liked this because this way, I will be able to keep my lenses when I upgrade the body in the future.
    But at the same time, I didn't understand it.:???:

    Rebel series use APS-C size sensor and 5D uses full frame sensor.
    How would they use same lenses? Doesn't the lens diameter change with the image size sensor?

    I am hoping somebody will explain this to me?

    Thanks:)
     
  2. Dao

    Dao No longer a newbie, moving up!

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    5D: EF mount lens only
    Rebel: EF and EF-S mount lens

    If you buy only EF lens, you can use the lens on any Canon EOS cameras including film based EOS cameras.

    Quoted from Wikipidea:
    "The "S" in EF-S stands for "short back focus", which means that the rear element of the lens is closer to the image sensor than on regular 35 mm SLR cameras."
     
  3. icassell

    icassell TPF Noob!

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    Canon actually has 2 variants on the lens mount ... the EF and the EF-S. The EF-S lenses are only useable on the crop-sensor cameras, whereas the EF mount is useable on any EOS camera. If you are thinking of upgrading your camera to a Full Frame body, buy only EF mount or be prepared to sell your EF-S lenses.
     
  4. iskoos

    iskoos TPF Noob!

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    I see... It makes more sense right now.
    The lense rebel series cameras come with is 18-55mm EF-S lense. This lense will NOT work on 5D because 5D only uses EF lenses...

    Alright so far... But can someone also explain if EF lenses have larger diameter than EF-S lenses?

    I am hoping you understand where I am coming from. I am trying to find out what determines the lens diameter...
     
  5. Dao

    Dao No longer a newbie, moving up!

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    why??
     
  6. iskoos

    iskoos TPF Noob!

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    So when somebody askes me the same thing one day, I do not have to ask the question of "why??" and be able to explain them instead...

    Do not get mad at me but I would like to learn things rather than memorizing them... When you truly learn what it is, you will never forget. If you memorize, you will forget it one day...

    It is just how me works...:)
     
  7. Big Mike

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

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    What, specifically, are you talking about when you say 'lens diameter'?
    The front of the lens? The diameter of the body? The mount?

    The mount is the same, but the actual size of the lens is determined by the design of the lens; the maximum aperture, the features (IS etc) and so on.

    One thing that does change between EF and EF-S lenses, is the size of of the image circle at the film plane (sensor). Since EF-S lenses are made for cameras with a smaller sensor, their image circle doesn't need to as big as the one that EF lenses need to create.
    This is why, if you did rig an EF-S lens to fit a fill frame camera, you would have a vignette on the corners.
     
  8. t00sl0w

    t00sl0w TPF Noob!

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    not to thread jack....but this may be relevant....

    is there a adapter for a 4/3 35mm to the EF mount?
     
  9. Dao

    Dao No longer a newbie, moving up!

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  10. JButler

    JButler TPF Noob!

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    The lens diameter doesn't matter. What you care about is the size of the image that's projected on the camera's sensor. EF-S lenses project a small image in the sensor. Large enough to fill up an APS-C, but too small for a full frame sensor. If you shot an EF-S lens on a 5D your images would come out as little circles.
     
  11. iskoos

    iskoos TPF Noob!

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    Well, the lens diameter does matter. You confirm this in your paragraph above. If the lens diameter would not matter then, they would make the full frame cameras work with tiny lenses that we see on P&S cameras. Do you think this would be possible?
    I am pretty sure we talk about the same thing but perhaps I couldn't explain myself well.

    Big Mike, your last paragraph is I guess what I was asking about: image circle. EF-S lenses create smaller image circle for smaller image sensors and EF lenses create larger ones deu to the full frame sensor size.
    When I was asking about lens diameter, I was asking in general but it looks like there is not one specific lens diameter we can talk about.
     
  12. Big Mike

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

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    There are probably hundreds of parts to a lens that have a diameter...you just needed to be more specific. ;)
     

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