The multi-element, spherical lens-based lens MUST DIE!!

Discussion in 'Digital Photography' started by RichA, Mar 2, 2011.

  1. RichA

    RichA Guest

    They must eliminate the multi-element lens. It is too heavy. It is
    too complex inside therefore TOO expensive. 14-17 elements? Why, in
    this day of hybrid aspherics and ED glass? Pentax makes a 400mm f4
    telescope with 4 elements that produces a highly-corrected (colour,
    astigmatism, spherical aberration) FLAT image across an entire medium
    format film plane. With FOUR elements! WHERE is the Nikon or Canon
    lens that can do that with so few elements? For about $3k. Takahashi
    (Japanese) has a similar lens. And those lenses do it diffraction-
    limited without stopping down! Multi-element lens systems based on
    spherical lenses are DINOSAURS.
     
    RichA, Mar 2, 2011
    #1
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  2. RichA

    Bruce Guest

    RichA <> wrote:
    >They must eliminate the multi-element lens. It is too heavy. It is
    >too complex inside therefore TOO expensive. 14-17 elements? Why, in
    >this day of hybrid aspherics and ED glass? Pentax makes a 400mm f4
    >telescope with 4 elements that produces a highly-corrected (colour,
    >astigmatism, spherical aberration) FLAT image across an entire medium
    >format film plane. With FOUR elements! WHERE is the Nikon or Canon
    >lens that can do that with so few elements? For about $3k. Takahashi
    >(Japanese) has a similar lens. And those lenses do it diffraction-
    >limited without stopping down! Multi-element lens systems based on
    >spherical lenses are DINOSAURS.



    You need to compare the MTF of those telescopes with the MTF of top
    quality fixed focus DSLR lenses of comparable focal lengths. I
    suspect that will give you the answer you need.
     
    Bruce, Mar 3, 2011
    #2
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  3. RichA

    shiva das Guest

    In article <>,
    Bruce <> wrote:

    > RichA <> wrote:
    > >They must eliminate the multi-element lens. It is too heavy. It is
    > >too complex inside therefore TOO expensive. 14-17 elements? Why, in
    > >this day of hybrid aspherics and ED glass? Pentax makes a 400mm f4
    > >telescope with 4 elements that produces a highly-corrected (colour,
    > >astigmatism, spherical aberration) FLAT image across an entire medium
    > >format film plane. With FOUR elements! WHERE is the Nikon or Canon
    > >lens that can do that with so few elements? For about $3k. Takahashi
    > >(Japanese) has a similar lens. And those lenses do it diffraction-
    > >limited without stopping down! Multi-element lens systems based on
    > >spherical lenses are DINOSAURS.

    >
    >
    > You need to compare the MTF of those telescopes with the MTF of top
    > quality fixed focus DSLR lenses of comparable focal lengths. I
    > suspect that will give you the answer you need.


    Or scratch your head a bit and consider that you are comparing zoom
    lenses with ludicrous throw ranges to highly-correct prime lenses.

    Which do you _expect_ is going to win? Especially comparing a 4-element
    prime with a 17-element zoom. That alone should tell you something.
    Massively fewer air-glass interfaces, no playing around with a slippery
    aperture, no cutting corners on the mount material stability... A few
    aspherical elements or ED glass aren't going to make the zooms any
    better.
     
    shiva das, Mar 3, 2011
    #3
  4. RichA

    RichA Guest

    On Mar 2, 7:44 pm, Bruce <> wrote:
    > RichA <> wrote:
    > >They must eliminate the multi-element lens.  It is too heavy.  It is
    > >too complex inside therefore TOO expensive. 14-17 elements?  Why, in
    > >this day of hybrid aspherics and ED glass?  Pentax makes a 400mm f4
    > >telescope with 4 elements that produces a highly-corrected (colour,
    > >astigmatism, spherical aberration) FLAT image across an entire medium
    > >format film plane.  With FOUR elements!  WHERE is the Nikon or Canon
    > >lens that can do that with so few elements?  For about $3k.  Takahashi
    > >(Japanese) has a similar lens.  And those lenses do it diffraction-
    > >limited without stopping down!  Multi-element lens systems based on
    > >spherical lenses are DINOSAURS.

    >
    > You need to compare the MTF of those telescopes with the MTF of top
    > quality fixed focus DSLR lenses of comparable focal lengths.  I
    > suspect that will give you the answer you need.


    A top quality 400mm DSLR lens is about $10,000 and still won't be
    diffraction-limited wide open.
     
    RichA, Mar 3, 2011
    #4
  5. RichA

    RichA Guest

    On Mar 3, 1:30 am, Paul Furman <> wrote:
    > RichA wrote:
    > > They must eliminate the multi-element lens.  It is too heavy.  It is
    > > too complex inside therefore TOO expensive. 14-17 elements?  Why, in
    > > this day of hybrid aspherics and ED glass?  Pentax makes a 400mm f4
    > > telescope with 4 elements that produces a highly-corrected (colour,
    > > astigmatism, spherical aberration) FLAT image across an entire medium
    > > format film plane.  With FOUR elements!  WHERE is the Nikon or Canon
    > > lens that can do that with so few elements?  For about $3k.  Takahashi
    > > (Japanese) has a similar lens.  And those lenses do it diffraction-
    > > limited without stopping down!  Multi-element lens systems based on
    > > spherical lenses are DINOSAURS.

    >
    > How do they do at close focus/macro distances?


    You can focus them as close as you want, with extender adapters.
    However, a lens optimized for infinity is going to have spherical
    aberration close up. In that case you will have to stop them down.

    > Fast autofocus?


    Big deal. It's like Canon and Nikon almost doubling lens prices for
    including I.S./V.R when other mfgs build it into the body of their
    cameras. MONEY!!!

    > Barrel/pincushion?


    Generally almost none.

    > Compact?


    The Takahashi and Pentax 400mm are slightly longer than say a Nikon
    lens, but by avoiding a severely curved negative element (as the Nikon
    needs to achieve that f.l. in a slightly smaller package) the optics
    can be made to a considerably higher standard for less cost.
     
    RichA, Mar 3, 2011
    #5
  6. RichA

    Bruce Guest

    RichA <> wrote:
    >On Mar 2, 7:44 pm, Bruce <> wrote:
    >> RichA <> wrote:
    >> >They must eliminate the multi-element lens.  It is too heavy.  It is
    >> >too complex inside therefore TOO expensive. 14-17 elements?  Why, in
    >> >this day of hybrid aspherics and ED glass?  Pentax makes a 400mm f4
    >> >telescope with 4 elements that produces a highly-corrected (colour,
    >> >astigmatism, spherical aberration) FLAT image across an entire medium
    >> >format film plane.  With FOUR elements!  WHERE is the Nikon or Canon
    >> >lens that can do that with so few elements?  For about $3k.  Takahashi
    >> >(Japanese) has a similar lens.  And those lenses do it diffraction-
    >> >limited without stopping down!  Multi-element lens systems based on
    >> >spherical lenses are DINOSAURS.

    >>
    >> You need to compare the MTF of those telescopes with the MTF of top
    >> quality fixed focus DSLR lenses of comparable focal lengths.  I
    >> suspect that will give you the answer you need.

    >
    >A top quality 400mm DSLR lens is about $10,000 and still won't be
    >diffraction-limited wide open.



    Then let's all shoot through telescopes and see how good they are.

    If this was such a good idea, people would be doing it already ...
     
    Bruce, Mar 3, 2011
    #6
  7. RichA

    RichA Guest

    On Mar 3, 8:38 am, Bruce <> wrote:
    > RichA <> wrote:
    > >On Mar 2, 7:44 pm, Bruce <> wrote:
    > >> RichA <> wrote:
    > >> >They must eliminate the multi-element lens. It is too heavy. It is
    > >> >too complex inside therefore TOO expensive. 14-17 elements? Why, in
    > >> >this day of hybrid aspherics and ED glass? Pentax makes a 400mm f4
    > >> >telescope with 4 elements that produces a highly-corrected (colour,
    > >> >astigmatism, spherical aberration) FLAT image across an entire medium
    > >> >format film plane. With FOUR elements! WHERE is the Nikon or Canon
    > >> >lens that can do that with so few elements? For about $3k. Takahashi
    > >> >(Japanese) has a similar lens. And those lenses do it diffraction-
    > >> >limited without stopping down! Multi-element lens systems based on
    > >> >spherical lenses are DINOSAURS.

    >
    > >> You need to compare the MTF of those telescopes with the MTF of top
    > >> quality fixed focus DSLR lenses of comparable focal lengths. I
    > >> suspect that will give you the answer you need.

    >
    > >A top quality 400mm DSLR lens is about $10,000 and still won't be
    > >diffraction-limited wide open.

    >
    > Then let's all shoot through telescopes and see how good they are.
    >
    > If this was such a good idea, people would be doing it already ...


    Kowa is the first to turn what is a basic, 2-element ED telescope into
    a telephoto lens. However, in order to have a flat photographic
    field, you need an extra element and you need some elements to achieve
    an erect, correctly orientated view. This can be accomplished with
    lenses, or (ideally) prisms. Selectively aspherizing just one
    surface of one element also allows the nullifying of residual
    aberrations in lens systems. I suggested that William Optics
    (company from Taiwan who make high-performance but reasonably priced
    apochromatic telescopes) go into that realm 3 years ago, but at the
    time, they said it wasn't part of their mandate. But they may jump in
    once Kowa does. As may Zeiss, Leica, even Nikon.
     
    RichA, Mar 3, 2011
    #7
  8. RichA

    RichA Guest

    On Mar 3, 12:09 pm, Paul Furman <> wrote:
    > RichA wrote:
    > > On Mar 3, 1:30 am, Paul Furman<>  wrote:
    > >> RichA wrote:
    > >>> They must eliminate the multi-element lens.  It is too heavy.  Itis
    > >>> too complex inside therefore TOO expensive. 14-17 elements?  Why, in
    > >>> this day of hybrid aspherics and ED glass?  Pentax makes a 400mm f4
    > >>> telescope with 4 elements that produces a highly-corrected (colour,
    > >>> astigmatism, spherical aberration) FLAT image across an entire medium
    > >>> format film plane.  With FOUR elements!  WHERE is the Nikon or Canon
    > >>> lens that can do that with so few elements?  For about $3k.  Takahashi
    > >>> (Japanese) has a similar lens.  And those lenses do it diffraction-
    > >>> limited without stopping down!  Multi-element lens systems based on
    > >>> spherical lenses are DINOSAURS.

    >
    > >> How do they do at close focus/macro distances?

    >
    > > You can focus them as close as you want, with extender adapters.
    > > However, a lens optimized for infinity is going to have spherical
    > > aberration close up.  In that case you will have to stop them down.

    >
    > OK so they don't work for stuff like birds filling the frame, the sort
    > of thing people would buy a 400mm prime for in terrestrial photography.
    >
    > >> Fast autofocus?

    >
    > > Big deal.  It's like Canon and Nikon almost doubling lens prices for
    > > including I.S./V.R when other mfgs build it into the body of their
    > > cameras.  MONEY!!!

    >
    > And camera body size.
    >
    > >> Barrel/pincushion?

    >
    > > Generally almost none.

    >
    > Even at close focus?


    Yes. Don't forget we are talking about long teles here.

    > >> Compact?

    >
    > > The Takahashi and Pentax 400mm are slightly longer than say a Nikon
    > > lens, but by avoiding a severely curved negative element (as the Nikon
    > > needs to achieve that f.l. in a slightly smaller package) the optics
    > > can be made to a considerably higher standard for less cost.

    >
    > If they are telephoto designs, I believe that means more elements and
    > more compact. Non-telephoto designs are huge.


    Rule of thumb, spherical elements mean needing more elements.
     
    RichA, Mar 3, 2011
    #8
  9. RichA

    RichA Guest

    On Mar 3, 8:38 am, Bruce <> wrote:
    > RichA <> wrote:
    > >On Mar 2, 7:44 pm, Bruce <> wrote:
    > >> RichA <> wrote:
    > >> >They must eliminate the multi-element lens. It is too heavy. It is
    > >> >too complex inside therefore TOO expensive. 14-17 elements? Why, in
    > >> >this day of hybrid aspherics and ED glass? Pentax makes a 400mm f4
    > >> >telescope with 4 elements that produces a highly-corrected (colour,
    > >> >astigmatism, spherical aberration) FLAT image across an entire medium
    > >> >format film plane. With FOUR elements! WHERE is the Nikon or Canon
    > >> >lens that can do that with so few elements? For about $3k. Takahashi
    > >> >(Japanese) has a similar lens. And those lenses do it diffraction-
    > >> >limited without stopping down! Multi-element lens systems based on
    > >> >spherical lenses are DINOSAURS.

    >
    > >> You need to compare the MTF of those telescopes with the MTF of top
    > >> quality fixed focus DSLR lenses of comparable focal lengths. I
    > >> suspect that will give you the answer you need.

    >
    > >A top quality 400mm DSLR lens is about $10,000 and still won't be
    > >diffraction-limited wide open.

    >
    > Then let's all shoot through telescopes and see how good they are.


    Modern Photography in 1977 tested a TeleVue (Pearl River, New York,
    maker of high-performance apochromatic telescopes) Renaissance
    telescope. This was a 4" aperture, 500mm f5.0 refractor retailing for
    about $2000.00. It beat every lens they had EVER tested when it came
    to contrast and resolution. TeleVue has had 6 interations
    (improvements) of that scope since then, each of them providing better
    performance. The scope is now called the NP101 and is similar to what
    is called the Petzval design, 2 main elements up front, a smaller
    doublet midway down the tube. And there are even better telescopes
    than the TeleVue available from places like AstroPhysics, TEC, etc.
    The average camera lens is corrected to about 1-2 waves (yellow-green
    light). The average telescope is 1/4 wave, a high-end scope like
    those mentioned is 1/10th wave. The mirror that went into the Hubble
    was 1/100th wave. The reason telescopes have to be so accurate is
    that unlike a camera lens that is used at what is called, Prime focus
    (no extra magnificational elements) a telescope may be used in
    conjunction with projection optics. Imaging trying to put a 10-20x
    teleconverter on a camera lens and trying to get an image out of it.
    They do it with telescopes all the time, to shoot planets.
     
    RichA, Mar 3, 2011
    #9
  10. RichA

    Bruce Guest

    RichA <> wrote:
    >On Mar 3, 8:38 am, Bruce <> wrote:
    >> RichA <> wrote:
    >> >On Mar 2, 7:44 pm, Bruce <> wrote:
    >> >> RichA <> wrote:
    >> >> >They must eliminate the multi-element lens. It is too heavy. It is
    >> >> >too complex inside therefore TOO expensive. 14-17 elements? Why, in
    >> >> >this day of hybrid aspherics and ED glass? Pentax makes a 400mm f4
    >> >> >telescope with 4 elements that produces a highly-corrected (colour,
    >> >> >astigmatism, spherical aberration) FLAT image across an entire medium
    >> >> >format film plane. With FOUR elements! WHERE is the Nikon or Canon
    >> >> >lens that can do that with so few elements? For about $3k. Takahashi
    >> >> >(Japanese) has a similar lens. And those lenses do it diffraction-
    >> >> >limited without stopping down! Multi-element lens systems based on
    >> >> >spherical lenses are DINOSAURS.

    >>
    >> >> You need to compare the MTF of those telescopes with the MTF of top
    >> >> quality fixed focus DSLR lenses of comparable focal lengths. I
    >> >> suspect that will give you the answer you need.

    >>
    >> >A top quality 400mm DSLR lens is about $10,000 and still won't be
    >> >diffraction-limited wide open.

    >>
    >> Then let's all shoot through telescopes and see how good they are.
    >>
    >> If this was such a good idea, people would be doing it already ...

    >
    >Kowa is the first to turn what is a basic, 2-element ED telescope into
    >a telephoto lens. However, in order to have a flat photographic
    >field, you need an extra element and you need some elements to achieve
    >an erect, correctly orientated view. This can be accomplished with
    >lenses, or (ideally) prisms. Selectively aspherizing just one
    >surface of one element also allows the nullifying of residual
    >aberrations in lens systems. I suggested that William Optics
    >(company from Taiwan who make high-performance but reasonably priced
    >apochromatic telescopes) go into that realm 3 years ago, but at the
    >time, they said it wasn't part of their mandate. But they may jump in
    >once Kowa does. As may Zeiss, Leica, even Nikon.



    Modifying a telescope so it can be used as a telephoto lens on a DSLR,
    as you say Kowa has done, means that it is no longer a telescope.

    At the risk of repeating myself, if this was such a good idea, people
    would be doing it already ...
     
    Bruce, Mar 3, 2011
    #10
  11. In rec.photo.digital Paul Furman <> wrote:

    >> The Takahashi and Pentax 400mm are slightly longer than say a Nikon
    >> lens, but by avoiding a severely curved negative element (as the Nikon
    >> needs to achieve that f.l. in a slightly smaller package) the optics
    >> can be made to a considerably higher standard for less cost.


    > If they are telephoto designs, I believe that means more elements and
    > more compact. Non-telephoto designs are huge.


    Or catadioptric.

    --
    Chris Malcolm
     
    Chris Malcolm, Mar 3, 2011
    #11
  12. RichA

    Bruce Guest

    RichA <> wrote:
    >On Mar 3, 8:38 am, Bruce <> wrote:
    >> RichA <> wrote:
    >> >On Mar 2, 7:44 pm, Bruce <> wrote:
    >> >> RichA <> wrote:
    >> >> >They must eliminate the multi-element lens. It is too heavy. It is
    >> >> >too complex inside therefore TOO expensive. 14-17 elements? Why, in
    >> >> >this day of hybrid aspherics and ED glass? Pentax makes a 400mm f4
    >> >> >telescope with 4 elements that produces a highly-corrected (colour,
    >> >> >astigmatism, spherical aberration) FLAT image across an entire medium
    >> >> >format film plane. With FOUR elements! WHERE is the Nikon or Canon
    >> >> >lens that can do that with so few elements? For about $3k. Takahashi
    >> >> >(Japanese) has a similar lens. And those lenses do it diffraction-
    >> >> >limited without stopping down! Multi-element lens systems based on
    >> >> >spherical lenses are DINOSAURS.

    >>
    >> >> You need to compare the MTF of those telescopes with the MTF of top
    >> >> quality fixed focus DSLR lenses of comparable focal lengths. I
    >> >> suspect that will give you the answer you need.

    >>
    >> >A top quality 400mm DSLR lens is about $10,000 and still won't be
    >> >diffraction-limited wide open.

    >>
    >> Then let's all shoot through telescopes and see how good they are.

    >
    >Modern Photography in 1977 tested a TeleVue (Pearl River, New York,
    >maker of high-performance apochromatic telescopes) Renaissance
    >telescope. This was a 4" aperture, 500mm f5.0 refractor retailing for
    >about $2000.00. It beat every lens they had EVER tested when it came
    >to contrast and resolution. TeleVue has had 6 interations
    >(improvements) of that scope since then, each of them providing better
    >performance. The scope is now called the NP101 and is similar to what
    >is called the Petzval design, 2 main elements up front, a smaller
    >doublet midway down the tube. And there are even better telescopes
    >than the TeleVue available from places like AstroPhysics, TEC, etc.
    >The average camera lens is corrected to about 1-2 waves (yellow-green
    >light). The average telescope is 1/4 wave, a high-end scope like
    >those mentioned is 1/10th wave. The mirror that went into the Hubble
    >was 1/100th wave. The reason telescopes have to be so accurate is
    >that unlike a camera lens that is used at what is called, Prime focus
    >(no extra magnificational elements) a telescope may be used in
    >conjunction with projection optics. Imaging trying to put a 10-20x
    >teleconverter on a camera lens and trying to get an image out of it.
    >They do it with telescopes all the time, to shoot planets.



    If all this is true, why aren't we all using telecopes instead of
    telephoto lenses?

    Perhaps because a telescope costing $2000 in 1977 would be way out of
    reach in today's money. Plus, it would produce an inverted image.
    Plus, there is a lot more to optical performance than resolution and
    contrast.

    You obviously have an obsession about telescopes. Don't worry, in a
    few days it will go away, and you will start ranting about something
    else that is completely unrelated, but equally implausible.

    Do try to smile. ;-)
     
    Bruce, Mar 4, 2011
    #12
  13. RichA

    Robert Coe Guest

    On Thu, 03 Mar 2011 20:20:42 -0600, Outing Trolls is FUN!
    <> wrote:
    : On Thu, 3 Mar 2011 10:19:12 -0800 (PST), RichA <>
    : wrote:
    :
    : >On Mar 3, 8:38 am, Bruce <> wrote:
    : >> RichA <> wrote:
    : >> >On Mar 2, 7:44 pm, Bruce <> wrote:
    : >> >> RichA <> wrote:
    : >> >> >They must eliminate the multi-element lens. It is too heavy. It is
    : >> >> >too complex inside therefore TOO expensive. 14-17 elements? Why, in
    : >> >> >this day of hybrid aspherics and ED glass? Pentax makes a 400mm f4
    : >> >> >telescope with 4 elements that produces a highly-corrected (colour,
    : >> >> >astigmatism, spherical aberration) FLAT image across an entire medium
    : >> >> >format film plane. With FOUR elements! WHERE is the Nikon or Canon
    : >> >> >lens that can do that with so few elements? For about $3k. Takahashi
    : >> >> >(Japanese) has a similar lens. And those lenses do it diffraction-
    : >> >> >limited without stopping down! Multi-element lens systems based on
    : >> >> >spherical lenses are DINOSAURS.
    : >>
    : >> >> You need to compare the MTF of those telescopes with the MTF of top
    : >> >> quality fixed focus DSLR lenses of comparable focal lengths. I
    : >> >> suspect that will give you the answer you need.
    : >>
    : >> >A top quality 400mm DSLR lens is about $10,000 and still won't be
    : >> >diffraction-limited wide open.
    : >>
    : >> Then let's all shoot through telescopes and see how good they are.
    : >>
    : >> If this was such a good idea, people would be doing it already ...
    : >
    : >Kowa is the first to turn what is a basic, 2-element ED telescope into
    : >a telephoto lens. However, in order to have a flat photographic
    : >field, you need an extra element and you need some elements to achieve
    : >an erect, correctly orientated view. This can be accomplished with
    : >lenses, or (ideally) prisms. Selectively aspherizing just one
    : >surface of one element also allows the nullifying of residual
    : >aberrations in lens systems. I suggested that William Optics
    : >(company from Taiwan who make high-performance but reasonably priced
    : >apochromatic telescopes) go into that realm 3 years ago, but at the
    : >time, they said it wasn't part of their mandate. But they may jump in
    : >once Kowa does. As may Zeiss, Leica, even Nikon.
    :
    : I suggest you read any "Optics 101" literature that is readily available
    : before you ever talk about anything even remotely related to the subject
    : again. Then you wouldn't so swiftly remove all doubts about your blatantly
    : obvious fool-troll status.

    I guess it had to come to this eventually: the group's two preeminent
    bullshitters ready to square off. Maybe it'll be worth watching. :^)

    Bob
     
    Robert Coe, Mar 5, 2011
    #13
  14. RichA

    Robert Coe Guest

    On Thu, 03 Mar 2011 20:25:16 -0600, Outing Trolls is FUN!
    <> wrote:
    : On Fri, 04 Mar 2011 01:04:51 +0000, Bruce <> wrote:
    :
    : >RichA <> wrote:
    : >>On Mar 3, 8:38 am, Bruce <> wrote:
    : >>> RichA <> wrote:
    : >>> >On Mar 2, 7:44 pm, Bruce <> wrote:
    : >>> >> RichA <> wrote:
    : >>> >> >They must eliminate the multi-element lens. It is too heavy. It is
    : >>> >> >too complex inside therefore TOO expensive. 14-17 elements? Why, in
    : >>> >> >this day of hybrid aspherics and ED glass? Pentax makes a 400mm f4
    : >>> >> >telescope with 4 elements that produces a highly-corrected (colour,
    : >>> >> >astigmatism, spherical aberration) FLAT image across an entire medium
    : >>> >> >format film plane. With FOUR elements! WHERE is the Nikon or Canon
    : >>> >> >lens that can do that with so few elements? For about $3k. Takahashi
    : >>> >> >(Japanese) has a similar lens. And those lenses do it diffraction-
    : >>> >> >limited without stopping down! Multi-element lens systems based on
    : >>> >> >spherical lenses are DINOSAURS.
    : >>>
    : >>> >> You need to compare the MTF of those telescopes with the MTF of top
    : >>> >> quality fixed focus DSLR lenses of comparable focal lengths. I
    : >>> >> suspect that will give you the answer you need.
    : >>>
    : >>> >A top quality 400mm DSLR lens is about $10,000 and still won't be
    : >>> >diffraction-limited wide open.
    : >>>
    : >>> Then let's all shoot through telescopes and see how good they are.
    : >>
    : >>Modern Photography in 1977 tested a TeleVue (Pearl River, New York,
    : >>maker of high-performance apochromatic telescopes) Renaissance
    : >>telescope. This was a 4" aperture, 500mm f5.0 refractor retailing for
    : >>about $2000.00. It beat every lens they had EVER tested when it came
    : >>to contrast and resolution. TeleVue has had 6 interations
    : >>(improvements) of that scope since then, each of them providing better
    : >>performance. The scope is now called the NP101 and is similar to what
    : >>is called the Petzval design, 2 main elements up front, a smaller
    : >>doublet midway down the tube. And there are even better telescopes
    : >>than the TeleVue available from places like AstroPhysics, TEC, etc.
    : >>The average camera lens is corrected to about 1-2 waves (yellow-green
    : >>light). The average telescope is 1/4 wave, a high-end scope like
    : >>those mentioned is 1/10th wave. The mirror that went into the Hubble
    : >>was 1/100th wave. The reason telescopes have to be so accurate is
    : >>that unlike a camera lens that is used at what is called, Prime focus
    : >>(no extra magnificational elements) a telescope may be used in
    : >>conjunction with projection optics. Imaging trying to put a 10-20x
    : >>teleconverter on a camera lens and trying to get an image out of it.
    : >>They do it with telescopes all the time, to shoot planets.
    : >
    : >
    : >If all this is true, why aren't we all using telecopes instead of
    : >telephoto lenses?
    : >
    : >Perhaps because a telescope costing $2000 in 1977 would be way out of
    : >reach in today's money. Plus, it would produce an inverted image.
    : >Plus, there is a lot more to optical performance than resolution and
    : >contrast.
    :
    :
    :
    : I suggest you read any "Optics 101" literature that is readily available
    : before you ever talk about anything even remotely related to the subject
    : again. Then you wouldn't so swiftly remove all doubts about your blatantly
    : obvious fool-troll status.

    Twice in the preceding five minutes you said exactly the same thing about
    Rich. I guess you really are nothing but a mindless trolling machine.

    Bob
     
    Robert Coe, Mar 5, 2011
    #14
  15. RichA

    PeterN Guest

    On 3/5/2011 9:12 PM, Eric Stevens wrote:
    > On Sat, 5 Mar 2011 16:41:57 -0500, "Neil Harrington"<>
    > wrote:
    >
    >>
    >> "RichA"<> wrote in message
    >> news:...
    >>> They must eliminate the multi-element lens. It is too heavy. It is
    >>> too complex inside therefore TOO expensive. 14-17 elements? Why, in
    >>> this day of hybrid aspherics and ED glass? Pentax makes a 400mm f4
    >>> telescope with 4 elements that produces a highly-corrected (colour,
    >>> astigmatism, spherical aberration) FLAT image across an entire medium
    >>> format film plane. With FOUR elements! WHERE is the Nikon or Canon
    >>> lens that can do that with so few elements?

    >>
    >> With such a narrow field of view and modest aperture it's relatively easy.
    >> Leitz made the legendary 400mm f/5 Telyt for the 1936 Olympics -- they made
    >> longer Telyts too, and I think they were all two-element lenses.

    >
    > See http://www.edbuziak.workzsites.com/lenses_Leica_Telyt_400_p3.html
    >
    > "Today, a couple of decades on, would I choose to use a Leitz Telyt
    > 400mm again... probably not as I’m now enjoying digital working,
    > and a recently purchased Nikon 70-200mm Vibration Reduction zoom
    > lens is getting far more use than all my long Leica lenses ever
    > did."
    >>


    The 70-200 has rapidly won first place in my bag. I often couple it with
    the 1.7 tele extender and have not observed any loss in quality. I have
    friends who use it with the new 2x Apo tele extender with favorable
    reports.
    Another interesting use for that lens is with extension tubes, for close
    up work.



    --
    Peter
     
    PeterN, Mar 6, 2011
    #15
  16. RichA

    Rich Guest

    On Mar 5, 4:41 pm, "Neil Harrington" <> wrote:
    > "RichA" <> wrote in message
    >
    > news:...
    >
    > > They must eliminate the multi-element lens.  It is too heavy.  It is
    > > too complex inside therefore TOO expensive. 14-17 elements?  Why, in
    > > this day of hybrid aspherics and ED glass?  Pentax makes a 400mm f4
    > > telescope with 4 elements that produces a highly-corrected (colour,
    > > astigmatism, spherical aberration) FLAT image across an entire medium
    > > format film plane.  With FOUR elements!  WHERE is the Nikon or Canon
    > > lens that can do that with so few elements?

    >
    > With such a narrow field of view and modest aperture it's relatively easy..
    > Leitz made the legendary 400mm f/5 Telyt for the 1936 Olympics -- they made
    > longer Telyts too, and I think they were all two-element lenses.
    >
    > > For about $3k.  Takahashi
    > > (Japanese) has a similar lens.  And those lenses do it diffraction-
    > > limited without stopping down!  Multi-element lens systems based on
    > > spherical lenses are DINOSAURS.

    >
    > OK, show us a nice f/1.4 four-element aspherical, or better yet an
    > ultrawide.


    That is a different matter, but, if you want wide coverage that has
    decent edges at f1.4 you KNOW aspherics are the only solution. They
    also reduce element counts.
     
    Rich, Mar 6, 2011
    #16
  17. RichA

    Rich Guest

    On Mar 3, 8:04 pm, Bruce <> wrote:
    > RichA <> wrote:
    > >On Mar 3, 8:38 am, Bruce <> wrote:
    > >> RichA <> wrote:
    > >> >On Mar 2, 7:44 pm, Bruce <> wrote:
    > >> >> RichA <> wrote:
    > >> >> >They must eliminate the multi-element lens. It is too heavy. It is
    > >> >> >too complex inside therefore TOO expensive. 14-17 elements? Why, in
    > >> >> >this day of hybrid aspherics and ED glass? Pentax makes a 400mm f4
    > >> >> >telescope with 4 elements that produces a highly-corrected (colour,
    > >> >> >astigmatism, spherical aberration) FLAT image across an entire medium
    > >> >> >format film plane. With FOUR elements! WHERE is the Nikon or Canon
    > >> >> >lens that can do that with so few elements? For about $3k. Takahashi
    > >> >> >(Japanese) has a similar lens. And those lenses do it diffraction-
    > >> >> >limited without stopping down! Multi-element lens systems based on
    > >> >> >spherical lenses are DINOSAURS.

    >
    > >> >> You need to compare the MTF of those telescopes with the MTF of top
    > >> >> quality fixed focus DSLR lenses of comparable focal lengths. I
    > >> >> suspect that will give you the answer you need.

    >
    > >> >A top quality 400mm DSLR lens is about $10,000 and still won't be
    > >> >diffraction-limited wide open.

    >
    > >> Then let's all shoot through telescopes and see how good they are.

    >
    > >Modern Photography in 1977 tested a TeleVue (Pearl River, New York,
    > >maker of high-performance apochromatic telescopes) Renaissance
    > >telescope.  This was a 4" aperture, 500mm f5.0 refractor retailing for
    > >about $2000.00.  It beat every lens they had EVER tested when it came
    > >to contrast and resolution.  TeleVue has had 6 interations
    > >(improvements) of that scope since then, each of them providing better
    > >performance.  The scope is now called the NP101 and is similar to what
    > >is called the Petzval design, 2 main elements up front, a smaller
    > >doublet midway down the tube.  And there are even better telescopes
    > >than the TeleVue available from places like AstroPhysics, TEC, etc.
    > >The average camera lens is corrected to about 1-2 waves (yellow-green
    > >light).  The average telescope is 1/4 wave, a high-end scope like
    > >those mentioned is 1/10th wave.  The mirror that went into the Hubble
    > >was 1/100th wave.  The reason telescopes have to be so accurate is
    > >that unlike a camera lens that is used at what is called, Prime focus
    > >(no extra magnificational elements) a telescope may be used in
    > >conjunction with projection optics.  Imaging trying to put a 10-20x
    > >teleconverter on a camera lens and trying to get an image out of it.
    > >They do it with telescopes all the time, to shoot planets.

    >
    > If all this is true, why aren't we all using telecopes instead of
    > telephoto lenses?
    >
    > Perhaps because a telescope costing $2000 in 1977 would be way out of
    > reach in today's money.  Plus, it would produce an inverted image.
    > Plus, there is a lot more to optical performance than resolution and
    > contrast.
    >
    > You obviously have an obsession about telescopes.  Don't worry, in a
    > few days it will go away, and you will start ranting about something
    > else that is completely unrelated, but equally implausible.  
    >
    > Do try to smile.  ;-)


    Obsession with instruments that have superior optical quality. Some
    microscopes meet that spec. Some telescopes do. Virtually no camera
    lenses do. But the use of a lens at an equivalent f.l. of
    25,000-50,000mm and getting quality results is so alien to camera
    users that there is little point in trying to educate them as to how
    such a thing is possible.
     
    Rich, Mar 6, 2011
    #17
  18. RichA

    Rich Guest

    On Mar 5, 10:06 pm, PeterN <> wrote:
    > On 3/5/2011 9:12 PM, Eric Stevens wrote:
    >
    >
    >
    > > On Sat, 5 Mar 2011 16:41:57 -0500, "Neil Harrington"<>
    > > wrote:

    >
    > >> "RichA"<>  wrote in message
    > >>news:....
    > >>> They must eliminate the multi-element lens.  It is too heavy.  Itis
    > >>> too complex inside therefore TOO expensive. 14-17 elements?  Why, in
    > >>> this day of hybrid aspherics and ED glass?  Pentax makes a 400mm f4
    > >>> telescope with 4 elements that produces a highly-corrected (colour,
    > >>> astigmatism, spherical aberration) FLAT image across an entire medium
    > >>> format film plane.  With FOUR elements!  WHERE is the Nikon or Canon
    > >>> lens that can do that with so few elements?

    >
    > >> With such a narrow field of view and modest aperture it's relatively easy.
    > >> Leitz made the legendary 400mm f/5 Telyt for the 1936 Olympics -- theymade
    > >> longer Telyts too, and I think they were all two-element lenses.

    >
    > > Seehttp://www.edbuziak.workzsites.com/lenses_Leica_Telyt_400_p3.html

    >
    > >    "Today, a couple of decades on, would I choose to use a Leitz Telyt
    > >     400mm again... probably not as I m now enjoying digital working,
    > >     and a recently purchased Nikon 70-200mm Vibration Reduction zoom
    > >     lens is getting far more use than all my long Leica lenses ever
    > >     did."

    >
    > The 70-200 has rapidly won first place in my bag. I often couple it with
    > the 1.7 tele extender and have not observed any loss in quality. I have
    > friends who use it with the new 2x Apo tele extender with favorable
    > reports.
    > Another interesting use for that lens is with extension tubes, for close
    > up work.
    >
    > --
    > Peter


    There is a simple way to check the quality. Are the images giving
    you exactly 1.7x or 2.0x the linear resolution with the extenders
    attached? Is the contrast the same as with the bare lens? I've used
    a Nikon 70-200mm f2.8 with and without a 1.7x extender. While the
    images were pretty decent, I would not say the telextended lens was as
    good proportionally as the bare lens. If someone can do this
    comparison, that would be good, but with resolution targets and not
    shots of birds, cats, etc., because there is no way to control those
    conditions. Also, using extension tubes is likely introducing
    spherical aberration, if the object is less than about 10ft away from
    the 70-200mm and you are using the 200mm at f2.8. In order to fix
    that you'd have to stop-down the lens or use an optical corrector
    specifically designed for close-up shooting.

    http://toothwalker.org/optics/spherical.html
     
    Rich, Mar 6, 2011
    #18
  19. RichA

    RichA Guest

    On Mar 3, 9:20 pm, Outing Trolls is FUN! <> wrote:
    > On Thu, 3 Mar 2011 10:19:12 -0800 (PST), RichA <>
    > wrote:
    >
    >
    >
    > >On Mar 3, 8:38 am, Bruce <> wrote:
    > >> RichA <> wrote:
    > >> >On Mar 2, 7:44 pm, Bruce <> wrote:
    > >> >> RichA <> wrote:
    > >> >> >They must eliminate the multi-element lens. It is too heavy. It is
    > >> >> >too complex inside therefore TOO expensive. 14-17 elements? Why, in
    > >> >> >this day of hybrid aspherics and ED glass? Pentax makes a 400mm f4
    > >> >> >telescope with 4 elements that produces a highly-corrected (colour,
    > >> >> >astigmatism, spherical aberration) FLAT image across an entire medium
    > >> >> >format film plane. With FOUR elements! WHERE is the Nikon or Canon
    > >> >> >lens that can do that with so few elements? For about $3k. Takahashi
    > >> >> >(Japanese) has a similar lens. And those lenses do it diffraction-
    > >> >> >limited without stopping down! Multi-element lens systems based on
    > >> >> >spherical lenses are DINOSAURS.

    >
    > >> >> You need to compare the MTF of those telescopes with the MTF of top
    > >> >> quality fixed focus DSLR lenses of comparable focal lengths. I
    > >> >> suspect that will give you the answer you need.

    >
    > >> >A top quality 400mm DSLR lens is about $10,000 and still won't be
    > >> >diffraction-limited wide open.

    >
    > >> Then let's all shoot through telescopes and see how good they are.

    >
    > >> If this was such a good idea, people would be doing it already ...

    >
    > >Kowa is the first to turn what is a basic, 2-element ED telescope into
    > >a telephoto lens.  However, in order to have a flat photographic
    > >field, you need an extra element and you need some elements to achieve
    > >an erect, correctly orientated view.  This can be accomplished with
    > >lenses, or (ideally) prisms.   Selectively aspherizing just one
    > >surface of one element also allows the nullifying of residual
    > >aberrations in lens systems.   I suggested that William Optics
    > >(company from Taiwan who make high-performance but reasonably priced
    > >apochromatic telescopes) go into that realm 3 years ago, but at the
    > >time, they said it wasn't part of their mandate.  But they may jump in
    > >once Kowa does.  As may Zeiss, Leica, even Nikon.

    >
    > I suggest you read any "Optics 101" literature that is readily available
    > before you ever talk about anything even remotely related to the subject
    > again. Then you wouldn't so swiftly remove all doubts about your blatantly
    > obvious fool-troll status.


    Here is some optics 101, bone-head. Read the second line.

    http://en.wikipedia.org/wiki/Aspheric_lens

    The asphere's more complex surface profile can reduce or eliminate
    spherical aberration and also reduce other optical aberrations
    compared to a simple lens. A single aspheric lens can often replace a
    much more complex multi-lens system. The resulting device is smaller
    and lighter, and possibly cheaper than the multi-lens design. Aspheric
    elements are used in the design of multi-element wide-angle and fast
    normal lenses to reduce aberrations. They are also used in combination
    with reflective elements (catadioptric systems) such as the aspherical
    Schmidt corrector plate used in the Schmidt cameras and the Schmidt-
    Cassegrain telescopes.
     
    RichA, Mar 6, 2011
    #19
  20. RichA

    PeterN Guest

    On 3/6/2011 11:41 AM, Rich wrote:
    > On Mar 5, 10:06 pm, PeterN<> wrote:
    >> On 3/5/2011 9:12 PM, Eric Stevens wrote:
    >>
    >>
    >>
    >>> On Sat, 5 Mar 2011 16:41:57 -0500, "Neil Harrington"<>
    >>> wrote:

    >>
    >>>> "RichA"<> wrote in message
    >>>> news:...
    >>>>> They must eliminate the multi-element lens. It is too heavy. It is
    >>>>> too complex inside therefore TOO expensive. 14-17 elements? Why, in
    >>>>> this day of hybrid aspherics and ED glass? Pentax makes a 400mm f4
    >>>>> telescope with 4 elements that produces a highly-corrected (colour,
    >>>>> astigmatism, spherical aberration) FLAT image across an entire medium
    >>>>> format film plane. With FOUR elements! WHERE is the Nikon or Canon
    >>>>> lens that can do that with so few elements?

    >>
    >>>> With such a narrow field of view and modest aperture it's relatively easy.
    >>>> Leitz made the legendary 400mm f/5 Telyt for the 1936 Olympics -- they made
    >>>> longer Telyts too, and I think they were all two-element lenses.

    >>
    >>> Seehttp://www.edbuziak.workzsites.com/lenses_Leica_Telyt_400_p3.html

    >>
    >>> "Today, a couple of decades on, would I choose to use a Leitz Telyt
    >>> 400mm again... probably not as I m now enjoying digital working,
    >>> and a recently purchased Nikon 70-200mm Vibration Reduction zoom
    >>> lens is getting far more use than all my long Leica lenses ever
    >>> did."

    >>
    >> The 70-200 has rapidly won first place in my bag. I often couple it with
    >> the 1.7 tele extender and have not observed any loss in quality. I have
    >> friends who use it with the new 2x Apo tele extender with favorable
    >> reports.
    >> Another interesting use for that lens is with extension tubes, for close
    >> up work.
    >>
    >> --
    >> Peter

    >
    > There is a simple way to check the quality. Are the images giving
    > you exactly 1.7x or 2.0x the linear resolution with the extenders
    > attached? Is the contrast the same as with the bare lens? I've used
    > a Nikon 70-200mm f2.8 with and without a 1.7x extender. While the
    > images were pretty decent, I would not say the telextended lens was as
    > good proportionally as the bare lens. If someone can do this
    > comparison, that would be good, but with resolution targets and not
    > shots of birds, cats, etc., because there is no way to control those
    > conditions. Also, using extension tubes is likely introducing
    > spherical aberration, if the object is less than about 10ft away from
    > the 70-200mm and you are using the 200mm at f2.8. In order to fix
    > that you'd have to stop-down the lens or use an optical corrector
    > specifically designed for close-up shooting.
    >
    > http://toothwalker.org/optics/spherical.html
    >


    For catalog or scientific recordings, you may or may not be right. It
    simply doesn't matter to me. For me, the system I described works fine.
    I couldn't care less about distortion as i try to do an interpretative
    shot.


    --
    Peter
     
    PeterN, Mar 6, 2011
    #20
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