Power Factors,,,Hmmmmm

Discussion in 'Digital Photography' started by Nick Beard, Jan 10, 2005.

  1. Nick Beard

    Nick Beard Guest

    Ok Smithers,, Now for some real math.

    I have two bodies, a D70 and a F100. I want to use a 200mm zoom with a 1.7
    converter. What I am trying to work out is the multiplication factor or X
    factor (dont ask!!..I like challenges ) from the standard view which would
    be 50mm for the film body and 35mm for the digital. Ok so far?

    I have no probs with the film calc but the digital X factor seem way to
    high. Here is what I have:

    Film - 200 X 1.7 + 340 / 50 = 6.8X. Ok this is perfect!

    Digital - 200 X 1.5 crop factor = 300 X 1.7 = 510 / 35 = 14.57X This seem
    way too much. If it is correct as it seems then this could explain why some
    digital products show a mad X factor a la digital camcorders and certain P&S
    jobs

    Ok let take your flack....ouch not too hard!!!!
    Nick Beard, Jan 10, 2005
    #1
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  2. Nick Beard wrote:
    > Ok Smithers,, Now for some real math.
    >
    > I have two bodies, a D70 and a F100. I want to use a 200mm zoom with

    a 1.7
    > converter. What I am trying to work out is the multiplication factor

    or X
    > factor (dont ask!!..I like challenges ) from the standard view which

    would
    > be 50mm for the film body and 35mm for the digital. Ok so far?
    >
    > I have no probs with the film calc but the digital X factor seem way

    to
    > high. Here is what I have:
    >
    > Film - 200 X 1.7 + 340 / 50 = 6.8X. Ok this is perfect!
    >
    > Digital - 200 X 1.5 crop factor = 300 X 1.7 = 510 / 35 = 14.57X This

    seem
    > way too much. If it is correct as it seems then this could explain

    why some
    > digital products show a mad X factor a la digital camcorders and

    certain P&S
    > jobs
    >


    Perspective yes, magnification no.
    Siddhartha Jain, Jan 10, 2005
    #2
    1. Advertising

  3. Nick Beard

    scott Guest

    "Nick Beard" <> wrote in message
    news:crujrk$ksg$1$
    > Ok Smithers,, Now for some real math.
    >
    > I have two bodies, a D70 and a F100. I want to use a 200mm zoom
    > with a 1.7 converter. What I am trying to work out is the
    > multiplication factor or X factor (dont ask!!..I like challenges )
    > from the standard view which would be 50mm for the film body and
    > 35mm for the digital. Ok so far?
    > I have no probs with the film calc but the digital X factor seem
    > way to high. Here is what I have:
    >
    > Film - 200 X 1.7 + 340 / 50 = 6.8X. Ok this is perfect!
    >
    > Digital - 200 X 1.5 crop factor = 300 X 1.7 = 510 / 35 = 14.57X This seem
    > way too much. If it is correct as it seems then this
    > could explain why some digital products show a mad X factor a la
    > digital camcorders and certain P&S jobs
    >
    > Ok let take your flack....ouch not too hard!!!!


    Your lens is 200 mm times 1.7 for the converter, that is 340 mm.

    That is 6.8X bigger than 50 mm or 9.7X bigger than 35 mm.
    scott, Jan 10, 2005
    #3
  4. Nick Beard

    Nick Beard Guest


    >
    > Your lens is 200 mm times 1.7 for the converter, that is 340 mm.
    >
    > That is 6.8X bigger than 50 mm or 9.7X bigger than 35 mm.


    You follow me for the top 'Film' calc o.k but the in the digital calc it
    would be the equiv of 510 not 340 mm in respects to 35 Film
    therefore it seems that 510 mm is 14.57X bigger than 35 mm (which provides a
    'standard view on digital D70)
    Remember I am taking the 'standard lens' as a datum point i.e film 50 mm /
    dig 35 mm.

    Next!!
    Nick Beard, Jan 10, 2005
    #4
  5. Nick Beard

    Nick Beard Guest


    > Your lens is 200 mm times 1.7 for the converter, that is 340 mm.
    >
    > That is 6.8X bigger than 50 mm or 9.7X bigger than 35 mm.


    Ah yes, but for the digital you are working with a 510 mm equiv in 35mm film
    due to the 1.5 x crop factor.
    I know were talking perceived focal length but this is what we have on the
    D70 with this setup. And the standard view on the D70 is still found using a
    35 mm lens which times 14.57X
    Nick Beard, Jan 10, 2005
    #5
  6. Nick Beard

    Jim Townsend Guest

    Nick Beard wrote:

    > Ok Smithers,, Now for some real math.
    >
    > I have two bodies, a D70 and a F100. I want to use a 200mm zoom with a 1.7
    > converter. What I am trying to work out is the multiplication factor or X
    > factor (dont ask!!..I like challenges ) from the standard view which would
    > be 50mm for the film body and 35mm for the digital. Ok so far?
    >
    > I have no probs with the film calc but the digital X factor seem way to
    > high. Here is what I have:
    >
    > Film - 200 X 1.7 + 340 / 50 = 6.8X. Ok this is perfect!
    >
    > Digital - 200 X 1.5 crop factor = 300 X 1.7 = 510 / 35 = 14.57X This seem
    > way too much. If it is correct as it seems then this could explain why some
    > digital products show a mad X factor a la digital camcorders and certain P&S
    > jobs
    >
    > Ok let take your flack....ouch not too hard!!!!


    First off, you're calculating field of view..

    Your formula should be:

    200mm x 1.7 = 340mm 340mm x 1.5 = 510mm 510mm/50mm = 10.2x

    But.. *You aren't gaining any magnification from the lens*. You're
    reducing the field of view due to the fact a portion of the image is
    falling outside boundaries of the sensor.

    You'll have an actual focal length of 350mm with the field of view of
    a 510mm lens.

    The 'magnification' doesn't take place until you *print* the image. This
    is hard to comprehend with digital cameras because the images produced
    have no physical size to make comparisons.

    Consider using a 35mm film camera, taking two identical shots, then
    cropping an APS sized chunk out of the middle of one of the negatives.

    Now, using an enlarger, make two 6"x 4" prints, one using the full negative
    and the other using the APS sized crop.

    To make a 4x6 print out of the piece you cut out, you'd have to enlarge
    the APS sized section 1.5x *more* than you have to enlarge the complete
    35mm negative.

    This extra enlarging at the time the image is printed is what causes the
    apparent magnification. The only difference is that with digital,
    the crop takes place at the time the image is shot. The crop occurs
    because s portion of the focused image falls outside of the sensor.

    The fact that part of the image didn't land on the sensor can't alter
    the focal length or the magnification of the lens in any way.
    Jim Townsend, Jan 10, 2005
    #6
  7. Nick Beard

    Nick Beard Guest

    Ooookay!!

    "scott" <> wrote in message
    news:geBEd.779$...
    > "Nick Beard" <> wrote in message
    > news:crujrk$ksg$1$
    >> Ok Smithers,, Now for some real math.
    >>
    >> I have two bodies, a D70 and a F100. I want to use a 200mm zoom
    >> with a 1.7 converter. What I am trying to work out is the
    >> multiplication factor or X factor (dont ask!!..I like challenges )
    >> from the standard view which would be 50mm for the film body and
    >> 35mm for the digital. Ok so far?
    >> I have no probs with the film calc but the digital X factor seem
    >> way to high. Here is what I have:
    >>
    >> Film - 200 X 1.7 + 340 / 50 = 6.8X. Ok this is perfect!
    >>
    >> Digital - 200 X 1.5 crop factor = 300 X 1.7 = 510 / 35 = 14.57X This seem
    >> way too much. If it is correct as it seems then this
    >> could explain why some digital products show a mad X factor a la
    >> digital camcorders and certain P&S jobs
    >>
    >> Ok let take your flack....ouch not too hard!!!!

    >
    > Your lens is 200 mm times 1.7 for the converter, that is 340 mm.
    >
    > That is 6.8X bigger than 50 mm or 9.7X bigger than 35 mm.
    >
    >
    Nick Beard, Jan 10, 2005
    #7
  8. Nick Beard

    scott Guest

    "Nick Beard" <> wrote in message
    news:cruoo8$3d9$1$
    >> Your lens is 200 mm times 1.7 for the converter, that is 340 mm.
    >>
    >> That is 6.8X bigger than 50 mm or 9.7X bigger than 35 mm.

    >
    > You follow me for the top 'Film' calc o.k but the in the digital
    > calc it would be the equiv of 510 not 340 mm in respects to 35 Film
    > therefore it seems that 510 mm is 14.57X bigger than 35 mm (which
    > provides a 'standard view on digital D70)


    No. If a 35 mm lens provides your "standard view" on a camera, then a 340
    mm lens will provide an image zoomed in by 9.7 times on this standard view,
    irrespective of whatever camera you are using.

    If on another camera you think 50 mm provides the "standard view", then a
    340 mm lens will provide an image zoomed in by 6.8 times on this standard
    view.

    If on another camera, you think 5 mm provides the "standard view" (ie P&S
    camera) then a 340 mm lens will provide an image zoomed in by 68 times
    compared to this standard view.
    scott, Jan 10, 2005
    #8
  9. Nick Beard

    Nick Beard Guest

    Thanks Jim, I understand your analogy well.
    It is just if you take the end perceived result of the 1.5X cropped 340 mm
    (i.e 510) and the 'standard perspective' of 35 mm lens on a Nikon digital
    slr, you come up with some whacky figures as opposed to the film body
    calculation :)

    "Jim Townsend" <> wrote in message
    news:...
    > Nick Beard wrote:
    >
    >> Ok Smithers,, Now for some real math.
    >>
    >> I have two bodies, a D70 and a F100. I want to use a 200mm zoom with a
    >> 1.7
    >> converter. What I am trying to work out is the multiplication factor or X
    >> factor (dont ask!!..I like challenges ) from the standard view which
    >> would
    >> be 50mm for the film body and 35mm for the digital. Ok so far?
    >>
    >> I have no probs with the film calc but the digital X factor seem way to
    >> high. Here is what I have:
    >>
    >> Film - 200 X 1.7 + 340 / 50 = 6.8X. Ok this is perfect!
    >>
    >> Digital - 200 X 1.5 crop factor = 300 X 1.7 = 510 / 35 = 14.57X This
    >> seem
    >> way too much. If it is correct as it seems then this could explain why
    >> some
    >> digital products show a mad X factor a la digital camcorders and certain
    >> P&S
    >> jobs
    >>
    >> Ok let take your flack....ouch not too hard!!!!

    >
    > First off, you're calculating field of view..
    >
    > Your formula should be:
    >
    > 200mm x 1.7 = 340mm 340mm x 1.5 = 510mm 510mm/50mm = 10.2x
    >
    > But.. *You aren't gaining any magnification from the lens*. You're
    > reducing the field of view due to the fact a portion of the image is
    > falling outside boundaries of the sensor.
    >
    > You'll have an actual focal length of 350mm with the field of view of
    > a 510mm lens.
    >
    > The 'magnification' doesn't take place until you *print* the image. This
    > is hard to comprehend with digital cameras because the images produced
    > have no physical size to make comparisons.
    >
    > Consider using a 35mm film camera, taking two identical shots, then
    > cropping an APS sized chunk out of the middle of one of the negatives.
    >
    > Now, using an enlarger, make two 6"x 4" prints, one using the full
    > negative
    > and the other using the APS sized crop.
    >
    > To make a 4x6 print out of the piece you cut out, you'd have to enlarge
    > the APS sized section 1.5x *more* than you have to enlarge the complete
    > 35mm negative.
    >
    > This extra enlarging at the time the image is printed is what causes the
    > apparent magnification. The only difference is that with digital,
    > the crop takes place at the time the image is shot. The crop occurs
    > because s portion of the focused image falls outside of the sensor.
    >
    > The fact that part of the image didn't land on the sensor can't alter
    > the focal length or the magnification of the lens in any way.
    >
    >
    Nick Beard, Jan 10, 2005
    #9
  10. Nick Beard

    Colin D Guest

    Nick Beard wrote:
    >
    > Ok Smithers,, Now for some real math.
    >
    > I have two bodies, a D70 and a F100. I want to use a 200mm zoom with a 1.7
    > converter. What I am trying to work out is the multiplication factor or X
    > factor (dont ask!!..I like challenges ) from the standard view which would
    > be 50mm for the film body and 35mm for the digital. Ok so far?
    >
    > I have no probs with the film calc but the digital X factor seem way to
    > high. Here is what I have:
    >
    > Film - 200 X 1.7 + 340 / 50 = 6.8X. Ok this is perfect!
    >
    > Digital - 200 X 1.5 crop factor = 300 X 1.7 = 510 / 35 = 14.57X This seem
    > way too much. If it is correct as it seems then this could explain why some
    > digital products show a mad X factor a la digital camcorders and certain P&S
    > jobs
    >
    > Ok let take your flack....ouch not too hard!!!!


    Your first equation should be 200 x 1.7 = 340: 340/50 = 6.8x (note the
    = instead of + as in your formula)

    Your second equation is wrong, since you have applied the crop factor
    twice - once when you set the standard lens at 35, and again when you
    included the 1.5x crop factor. If you include the 1.5x crop factor then
    you must use the 50mm lens in the equation.

    Colin
    Colin D, Jan 11, 2005
    #10
  11. Nick Beard

    Nick Beard Guest

    Now this makes a little more sense, thanks. I thought I was applying it
    twice but I could'nt see where. And thanks for pointing out my typo + istead
    of =. I hit the 'shift' key to much, I knew what I meant though.:)

    So the 'manipulated' X factor is 10.2X as stated by Jim. In any event it is
    greater than 6.8X on the Film body.

    Cool!


    "Colin D" <ColinD@killspam.127.0.0.1> wrote in message
    news:41E32013.3CD88390@killspam.127.0.0.1...
    >
    >
    > Nick Beard wrote:
    >>
    >> Ok Smithers,, Now for some real math.
    >>
    >> I have two bodies, a D70 and a F100. I want to use a 200mm zoom with a
    >> 1.7
    >> converter. What I am trying to work out is the multiplication factor or X
    >> factor (dont ask!!..I like challenges ) from the standard view which
    >> would
    >> be 50mm for the film body and 35mm for the digital. Ok so far?
    >>
    >> I have no probs with the film calc but the digital X factor seem way to
    >> high. Here is what I have:
    >>
    >> Film - 200 X 1.7 + 340 / 50 = 6.8X. Ok this is perfect!
    >>
    >> Digital - 200 X 1.5 crop factor = 300 X 1.7 = 510 / 35 = 14.57X This
    >> seem
    >> way too much. If it is correct as it seems then this could explain why
    >> some
    >> digital products show a mad X factor a la digital camcorders and certain
    >> P&S
    >> jobs
    >>
    >> Ok let take your flack....ouch not too hard!!!!

    >
    > Your first equation should be 200 x 1.7 = 340: 340/50 = 6.8x (note the
    > = instead of + as in your formula)
    >
    > Your second equation is wrong, since you have applied the crop factor
    > twice - once when you set the standard lens at 35, and again when you
    > included the 1.5x crop factor. If you include the 1.5x crop factor then
    > you must use the 50mm lens in the equation.
    >
    > Colin
    Nick Beard, Jan 11, 2005
    #11
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