24-85mm 3.5-4.5 vs off-brand 24-70mm 2.8

Discussion in 'Nikon Lenses' started by EchoingWhisper, Jun 16, 2012.

  1. Nikon_Josh

    Nikon_Josh TPF Noob!

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    I wasn't going to explain this to him, but then I realised I couldn't be bothered to waste my breath! :lol:


     
  2. EchoingWhisper

    EchoingWhisper TPF Noob!

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    I mean, I am likely to buy a D600 if it comes, that's why I needed to talk about equivalence. I just want some time to decide. If I were to buy my current setup immediately after I made up my mind before, I would have gotten a totally different setup. More time to decide means less wrong choices. Sorry for not stating that if I'm not clear.
     
  3. chris

    chris No longer a newbie, moving up!

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    I will try one last time.

    'Equivalence' is telling you what f-stop you need to set on a FX lens on a FX body to get the same DoF as a DX lens of the same focal length on a DX body. It does not change the fundamental properties of a lens - the maximum f-stops of the lenses are what they are because of the lens design and do not change with different formats. The differences are that FX lenses have a larger image circle than DX lenses so that they can adequately cover the larger format. As format size increases so a lens has to be stopped down further to give a particular DoF compared with a smaller format.

    You do not need to use equivalence just because you might buy a FX body - you just need to understand that a DX lens will not cover the full FX format satisfactorily
    but even if it did it would still have the same maximum f-stop as when used on a DX body.

    'Equilivance' as you are using it is a means of determining what lens setting to reproduce DoF when using different formats - it is not some magic formula that can change the characteristics of a lens between formats and cannot be used to compare two lens in the way that you are doing.

    Over and out.
     
  4. EchoingWhisper

    EchoingWhisper TPF Noob!

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    You need to crop the DX lens anyway if you put it on a FX lens, that's why you need equivalence.
     

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