Re: F4-5.6 sweet spot for APS-C cameras?

Discussion in 'Digital Photography' started by PeterN, Jul 16, 2011.

  1. PeterN

    PeterN Guest

    On 7/15/2011 6:22 PM, Savageduck wrote:
    > On 2011-07-15 14:49:54 -0700, Alfred Molon <> said:
    >
    >> While reading this lens review:
    >> http://www.photozone.de/canon-eos/515-sigma816f4556apsc?start=1
    >>
    >> I ran into this:
    >> "Please note that f/4-5.6 is the APS-C sweet spot where diffraction has
    >> no real impact yet and (center) aberrations are already well corrected."
    >>
    >> and if you look at the MTF diagrams you'll notice that the centre and
    >> border resolution are highest at F4.5 and drop with increasing F-number.
    >>
    >> I wouldn't have imagined that diffraction already starts impacting the
    >> resolution at F5 for APS-C cameras.

    >
    > I suspect they are addressing the lens in question, the Sigma AF 8-16mm
    > f/4.5-5.6, mounted on the 50D they used for their tests.
    >
    > That is an ultra wide lens and I seriously doubt there would be any
    > noticeable diffraction issues even if stopped down to f/8-f/11.
    >
    > There is only so much pixel peeping one can do.
    >
    > ...and reading further it seems the most consistent results with this
    > particular lens are to be had at f/8 through the zoom range.
    >


    However, the copy I tested has significant CA on the edges, when wide open.


    --
    Peter
     
    PeterN, Jul 16, 2011
    #1
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  2. PeterN

    PeterN Guest

    On 7/15/2011 10:49 PM, Savageduck wrote:
    > On 2011-07-15 19:35:17 -0700, PeterN <> said:
    >
    >> On 7/15/2011 6:22 PM, Savageduck wrote:
    >>> On 2011-07-15 14:49:54 -0700, Alfred Molon <>
    >>> said:
    >>>
    >>>> While reading this lens review:
    >>>> http://www.photozone.de/canon-eos/515-sigma816f4556apsc?start=1
    >>>>
    >>>> I ran into this:
    >>>> "Please note that f/4-5.6 is the APS-C sweet spot where diffraction has
    >>>> no real impact yet and (center) aberrations are already well
    >>>> corrected."
    >>>>
    >>>> and if you look at the MTF diagrams you'll notice that the centre and
    >>>> border resolution are highest at F4.5 and drop with increasing
    >>>> F-number.
    >>>>
    >>>> I wouldn't have imagined that diffraction already starts impacting the
    >>>> resolution at F5 for APS-C cameras.
    >>>
    >>> I suspect they are addressing the lens in question, the Sigma AF 8-16mm
    >>> f/4.5-5.6, mounted on the 50D they used for their tests.
    >>>
    >>> That is an ultra wide lens and I seriously doubt there would be any
    >>> noticeable diffraction issues even if stopped down to f/8-f/11.
    >>>
    >>> There is only so much pixel peeping one can do.
    >>>
    >>> ...and reading further it seems the most consistent results with this
    >>> particular lens are to be had at f/8 through the zoom range.
    >>>

    >>
    >> However, the copy I tested has significant CA on the edges, when wide
    >> open.

    >
    > Alfred seems to have his eye on this Sigma.
    >
    > I'll just stick with my Tokina 11-16mm f/2.8.
    >


    I have the Nikon 10.5. It's a semi-fisheye, but converts in software to
    rectilinear.


    --
    Peter
     
    PeterN, Jul 16, 2011
    #2
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  3. PeterN

    PeterN Guest

    On 7/19/2011 1:31 PM, Neil Harrington wrote:
    > PeterN wrote:
    >> On 7/15/2011 10:49 PM, Savageduck wrote:
    >>> On 2011-07-15 19:35:17 -0700, PeterN<>
    >>> said:
    >>>> On 7/15/2011 6:22 PM, Savageduck wrote:
    >>>>> On 2011-07-15 14:49:54 -0700, Alfred Molon<>
    >>>>> said:
    >>>>>
    >>>>>> While reading this lens review:
    >>>>>> http://www.photozone.de/canon-eos/515-sigma816f4556apsc?start=1
    >>>>>>
    >>>>>> I ran into this:
    >>>>>> "Please note that f/4-5.6 is the APS-C sweet spot where
    >>>>>> diffraction has no real impact yet and (center) aberrations are
    >>>>>> already well corrected."
    >>>>>>
    >>>>>> and if you look at the MTF diagrams you'll notice that the centre
    >>>>>> and border resolution are highest at F4.5 and drop with increasing
    >>>>>> F-number.
    >>>>>>
    >>>>>> I wouldn't have imagined that diffraction already starts
    >>>>>> impacting the resolution at F5 for APS-C cameras.
    >>>>>
    >>>>> I suspect they are addressing the lens in question, the Sigma AF
    >>>>> 8-16mm f/4.5-5.6, mounted on the 50D they used for their tests.
    >>>>>
    >>>>> That is an ultra wide lens and I seriously doubt there would be any
    >>>>> noticeable diffraction issues even if stopped down to f/8-f/11.
    >>>>>
    >>>>> There is only so much pixel peeping one can do.
    >>>>>
    >>>>> ...and reading further it seems the most consistent results with
    >>>>> this particular lens are to be had at f/8 through the zoom range.
    >>>>>
    >>>>
    >>>> However, the copy I tested has significant CA on the edges, when
    >>>> wide open.
    >>>
    >>> Alfred seems to have his eye on this Sigma.
    >>>
    >>> I'll just stick with my Tokina 11-16mm f/2.8.
    >>>

    >>
    >> I have the Nikon 10.5. It's a semi-fisheye, but converts in software
    >> to rectilinear.

    >
    > Yep. I have that too, and "de-fishing" it in Nikon Capture 4, NX or NX2
    > works remarkably well. It's one of my favorite lenses. Sure glad I bought it
    > when I did, when I look at prices now. I think I paid something like $530
    > for mine.


    After I make my buying decision, I don't care about the cost. I looked
    after your posting and was amazed. Since I bought it about three or four
    years ago, I probably paid around what you did. They are selling used
    for more than you paid. Although I don't use it often I think it's a fun
    lens and am happy to have it.


    --
    Peter
     
    PeterN, Jul 19, 2011
    #3
  4. Alfred Molon <> wrote:
    > In article <>, Neil
    > Harrington says...
    >> I have that too, and "de-fishing" it in Nikon Capture 4, NX or NX2
    >> works remarkably well.


    > I had a look at some fisheye to rectilinear conversion examples (8mm
    > lens) and noticed that you lose a lot of image - only the central part
    > is preserved. For that reason I would avoid a fisheye lens.


    That's the negative side. The positive side is that you'll still end
    up with a wider angle shot than any linear wide angle lens will give
    you. And of course you also get the fisheye mapping for those
    circumstances when it's useful -- for example it's an approximation to
    the volume-preserving mapping transformation offered in some of the
    projection conversion programs like DXO.

    --
    Chris Malcolm
     
    Chris Malcolm, Jul 20, 2011
    #4
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