Depth of field

Discussion in 'Digital Photography' started by rda, Jan 1, 2005.

  1. rda

    rda Guest

    Another question about the Sigma 20mm 1.8 (I just cannot afford the Canon
    17-40L).

    If I use f1.8 from a distance of around 20' from my subject would a group
    shot be sharp, or would I have to stop down?

    Sorry to bother you guys all the time.


    Happy New Year !

    --
    rda
    www.rdaphoto.co.uk
    rda, Jan 1, 2005
    #1
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  2. rda wrote:
    > Another question about the Sigma 20mm 1.8 (I just cannot afford the
    > Canon 17-40L).
    >
    > If I use f1.8 from a distance of around 20' from my subject would a
    > group shot be sharp, or would I have to stop down?
    >
    > Sorry to bother you guys all the time.
    >
    >
    > Happy New Year !


    If they were all the same distance from the lens they should all be in
    focus, there are a lot of other factors related to sharpness.

    If they were standing one behind the other a couple of feet apart, then
    the answer is you would need to stop down.

    --
    Joseph Meehan

    26 + 6 = 1 It's Irish Math
    Joseph Meehan, Jan 1, 2005
    #2
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  3. rda

    dylan Guest

    any use ? http://www.dofmaster.com/dofjs.html

    "rda" <> wrote in message
    news:...
    > Another question about the Sigma 20mm 1.8 (I just cannot afford the Canon
    > 17-40L).
    >
    > If I use f1.8 from a distance of around 20' from my subject would a group
    > shot be sharp, or would I have to stop down?
    >
    > Sorry to bother you guys all the time.
    >
    >
    > Happy New Year !
    >
    > --
    > rda
    > www.rdaphoto.co.uk
    >
    >
    dylan, Jan 1, 2005
    #3
  4. rda

    rda Guest

    "dylan" <> wrote in message
    news:cr6hnm$kv$...
    > any use ? http://www.dofmaster.com/dofjs.html
    >


    WOW, great link.

    It would seem that for 20' the depth of field would be from 13.2' - 41.2'.

    Thanks

    --
    rda
    www.rdaphoto.co.uk - comments welcomed (on the photos, I know the site is
    crap)
    rda, Jan 1, 2005
    #4
  5. rda

    skroob Guest

    I am looking into this lens myself, and have a question or two for the
    group.

    I have a D70 with the following lenses (18-70mm 3.5/4.5 DX, 70-300 4/5.6 ED,
    28mm 3.5 PC, Sigma 12-24mm 4.5/5.6)

    I was looking at adding the Sigma 20mm 1.8 to cover me in low-light
    situations where my SB-800 flash would be frowned upon (such as in a
    Cathedral).

    I should mention at this point that I shoot architecture 95% of the time,
    where its important for great sharpness and elimination of depth of field
    (not a problem set to infinity focus). However, with this lens, i want to
    get into artistic and portrait photography.

    Is this a wise choice?

    Thanks in advance.


    "rda" <> wrote in message
    news:...
    > Another question about the Sigma 20mm 1.8 (I just cannot afford the Canon
    > 17-40L).
    >
    > If I use f1.8 from a distance of around 20' from my subject would a group
    > shot be sharp, or would I have to stop down?
    >
    > Sorry to bother you guys all the time.
    >
    >
    > Happy New Year !
    >
    > --
    > rda
    > www.rdaphoto.co.uk
    >
    >
    skroob, Jan 1, 2005
    #5
  6. rda

    rda Guest

    "skroob" <> wrote in message
    news:gtBBd.36341$...
    > I am looking into this lens myself, and have a question or two for the
    > group.
    >
    > I have a D70 with the following lenses (18-70mm 3.5/4.5 DX, 70-300 4/5.6

    ED,
    > 28mm 3.5 PC, Sigma 12-24mm 4.5/5.6)
    >
    > I was looking at adding the Sigma 20mm 1.8 to cover me in low-light
    > situations where my SB-800 flash would be frowned upon (such as in a
    > Cathedral).
    >
    > I should mention at this point that I shoot architecture 95% of the time,
    > where its important for great sharpness and elimination of depth of field
    > (not a problem set to infinity focus). However, with this lens, i want to
    > get into artistic and portrait photography.
    >
    > Is this a wise choice?
    >


    I found a few sample images taken with this lens on pbase.
    http://search.pbase.com/search?q=20mm 1.8&b=Search Photos&c=sp

    Note, only some are taken with the Sigma.



    --
    rda
    www.rdaphoto.co.uk comments welcome (on the photos, the site is crap)
    rda, Jan 1, 2005
    #6
  7. "rda" <> wrote in message
    news:...
    >
    > "dylan" <> wrote in message
    > news:cr6hnm$kv$...
    >> any use ? http://www.dofmaster.com/dofjs.html
    >>

    >
    > WOW, great link.
    >
    > It would seem that for 20' the depth of field would be from 13.2' -
    > 41.2'.


    Yes, theoretically in the 14-34 feet range everything would be
    perfectly in focus, but I doubt the lens will perform uniformly
    throughout the Field of view when used wide open...

    Bart
    Bart van der Wolf, Jan 1, 2005
    #7
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