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Thread: Crop Factor. Still very confused..

  1. #1

    Default Crop Factor. Still very confused..

    Hi guys.. I know this has been talked about in many threads already but I am still confused. what with the DX FX body yada yada.. I think the answer to this question will immediately clear up all my confusion:

    If I use a DX lens set at 18mm on a DX body and I use a FX lens set at 18mm on a DX body. Will I get the same field of view?

    Straight forward answers will be very much appreciated.

    Thanks

  2. #2

    Default Re: Crop Factor. Still very confused..

    Quote Originally Posted by teojm37 View Post
    Hi guys.. I know this has been talked about in many threads already but I am still confused. what with the DX FX body yada yada.. I think the answer to this question will immediately clear up all my confusion:

    If I use a DX lens set at 18mm on a DX body and I use a FX lens set at 18mm on a DX body. Will I get the same field of view?

    Straight forward answers will be very much appreciated.

    Thanks
    No, you will not get the same field of view.

  3. #3
    Senior Member ZerocoolAstra's Avatar
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    Default Re: Crop Factor. Still very confused..

    Quote Originally Posted by chocnoodles View Post
    No, you will not get the same field of view.
    says who?

    If you use the same type of camera (DX), mouting an FX lens and DX lens with the same stated focal length (eg. 18mm) will give you the same field of view.
    Exploring! :)

  4. #4
    Senior Member ZerocoolAstra's Avatar
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    Default Re: Crop Factor. Still very confused..

    TS, I would advise you to Google up a few terms, such as "image circle" and "crop factor".
    There are actually quite detailed explanations online about the differences between FX and DX (cameras and lenses).

  5. #5

    Default Re: Crop Factor. Still very confused..

    Yea I did actually.. But many sources give my conflicting information. Such is an example of the dude above..

  6. #6

    Default Re: Crop Factor. Still very confused..

    Quote Originally Posted by ZerocoolAstra View Post
    says who?

    If you use the same type of camera (DX), mouting an FX lens and DX lens with the same stated focal length (eg. 18mm) will give you the same field of view.
    Says me~ .

    His questions goes: If I use a DX lens set at 18mm on a DX body and I use a FX lens set at 18mm on a DX body. Will I get the same field of view?

    Unless I am reading it wrongly.

  7. #7

    Default Re: Crop Factor. Still very confused..

    Hi, I think FX circular image encompassing the DX sensor will be cropped by the DX sensor equivalent to the size of the circular image of DX lens on DX sensor where there is cropping. The result is same FOV.

  8. #8

  9. #9
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    Default Re: Crop Factor. Still very confused..

    It's the camera that matters. DX lens probably refer to lens that can only mount on DX camera.

  10. #10
    Senior Member wildcat's Avatar
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    Default Re: Crop Factor. Still very confused..

    Quote Originally Posted by ZerocoolAstra View Post
    says who?

    If you use the same type of camera (DX), mouting an FX lens and DX lens with the same stated focal length (eg. 18mm) will give you the same field of view.
    ZCA is correct.

    When you mount an 18mm FX lens on a DX camera, it will give you an equivalent of 18mm x 1.5 = 27mm equiv (or 76 degrees angle of view).

    When you mount an 18mm DX lens on a DX camera, it will also give you an equivalent of 18mm x 1.5 = 27mm equiv (or 76 degrees angle of view) also.

    It is only when you mount an 18mm FX lens on an FX camera, then it will give you an 18mm equiv (or 100 degrees angle of view).

  11. #11
    Senior Member wildcat's Avatar
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    Default Re: Crop Factor. Still very confused..

    Quote Originally Posted by chocnoodles View Post
    Says me~ .

    His questions goes: If I use a DX lens set at 18mm on a DX body and I use a FX lens set at 18mm on a DX body. Will I get the same field of view?

    Unless I am reading it wrongly.
    Regardless of whether you use DX lens or FX lens on a DX body, you will have to x1.5 for the crop factor. So 18mm with the 1.5 multiplier will apply because both times, you are using DX body.

    When you are using FX body, then you don't use the multiplier.

  12. #12

    Default Re: Crop Factor. Still very confused..

    Quote Originally Posted by chocnoodles View Post
    Says me~ .

    His questions goes: If I use a DX lens set at 18mm on a DX body and I use a FX lens set at 18mm on a DX body. Will I get the same field of view?

    Unless I am reading it wrongly.
    Just so you know, the crop factor still applies for a DX lens on a DX body. I think that's where you are confused

  13. #13

    Default Re: Crop Factor. Still very confused..

    Yep.
    I think I'm no longer confused!
    YAY!!

    Thanks guys.

  14. #14
    Senior Member ZerocoolAstra's Avatar
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    Default Re: Crop Factor. Still very confused..

    Quote Originally Posted by chocnoodles View Post
    Says me~ .

    His questions goes: If I use a DX lens set at 18mm on a DX body and I use a FX lens set at 18mm on a DX body. Will I get the same field of view?

    Unless I am reading it wrongly.
    wildcat has explained quite clearly already... No need for me to photocopy his reply

    hope it's clear now for everyone.
    Last edited by ZerocoolAstra; 12th September 2010 at 12:36 AM. Reason: error in original post.
    Exploring! :)

  15. #15
    Member enzeru21's Avatar
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    Default Re: Crop Factor. Still very confused..

    its the body my fren, not the lens~!!
    enzeru21 Canon 500D |Tamron17-50mm f/2.8| Sigma30mm f/1.4 | 580EX II
    mylightedreams

  16. #16

    Default Re: Crop Factor. Still very confused..

    Quote Originally Posted by chocnoodles View Post
    Says me~ .

    His questions goes: If I use a DX lens set at 18mm on a DX body and I use a FX lens set at 18mm on a DX body. Will I get the same field of view?

    Unless I am reading it wrongly.
    You're reading it right, but understanding it wrongly.
    Alpha

  17. #17

    Default Re: Crop Factor. Still very confused..

    Really good video showing the difference of a cropped vs full frame sensor with various lenses. The video shows the Canon 5D Mk II (FF) vs the Canon 7D (1.6 crop), but it will be similar for Nikon, etc.



    SeldomHere
    7D | 17-55 2.8 | 18-135 | 50 1.4
    5DMkII | 14 L 2.8 | 24-105 L 4 | 70-200 L 2.8 | 100 L 2.8 Macro

  18. #18
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    Default Re: Crop Factor. Still very confused..

    then can you mount a DX Lens on a FX body ?

  19. #19
    Senior Member wildcat's Avatar
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    Default Re: Crop Factor. Still very confused..

    Quote Originally Posted by weegk View Post
    then can you mount a DX Lens on a FX body ?
    Yes but imagine if your lens was designed for 76 degrees of view, but you are trying to take 100 degrees of view. There should be approx 24 degrees of "black" space which will be very bad vignetting.

    On the other hand, using a FX lens on DX body means you are wasting 24 degrees of good lens space because your lens is capable of taking 100 degrees, but you're only using 76 degrees of it. Your picture will come out nice with no problem, which is why it's OK (sometimes preferable) to mount FX lens on DX body, but very seldom you see people doing it the other way round because black round circle around your picture.
    Last edited by wildcat; 12th September 2010 at 05:23 AM.

  20. #20
    Moderator daredevil123's Avatar
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    Default Re: Crop Factor. Still very confused..

    Quote Originally Posted by weegk View Post
    then can you mount a DX Lens on a FX body ?
    Yes you can. If Nikon DX lenses were mounted on newer FX cams (D700 D3/D3s), the cams will recognize the lens and automatically go into DX mode and crop the image for the DX sensor size.

    In options, you can turn off this auto detection and force the camera to use the full FX sensor all the time. Lenses meant for DX will work with the full FX sensor for a portion of the zoom range. For example, the Tokina 11-16 when mounted on a FX cam, will show heavy vignetting 11-15mm but it is fully usable at 16mm on a FX body.

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