DF / FX and aperture question

Started Sep 28, 2012 | Discussions thread
CarstenKostrzewa
New MemberPosts: 17
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Re: DF / FX and aperture question
In reply to mainger, Sep 28, 2012

I am not sure, whether this is, what you are actually asking for. So just to be sure you said, you were interested in portrait lenses for your D7000. It is correct that a 50mm F1.4 lens used on a D7000 "behaves" like a 75mm F2.0 lens on a full frame camera like the D600, i.e. the lens has a field of view which is equivalent to 75mm and it produces background blur (which is interesting for portraits) that is equivalent to F2.0 on a full frame camera. That said, if you actually use FX and DX lenses on a D7000, the focal length and the aperature are what they are, regardless of whether the lens is FX or DX.

BTW: if you are interested dependency between background blur and sensor sizes, I just published an article here at dpreview under: http://www.dpreview.com/articles/6091822765/background-blur-and-its-relationship-to-sensor-size

mainger wrote:
Bingo! This one makes it very clear, thanks a lot!

Cheers!

slimandy wrote:

Another way of looking at it.....

For an 85mm lens to have an f1.4 aperture it needs a physical opening of about 61mm....
85/61 = f1.4 (ish, 1.3934)

So if you work out the focal length equivalent is 85*1.5 = 127.7, the equivalent relative aperture is....

127.5/61 = f2 (ish, 2.09)

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