What does "too deep" mean WRT an adapter?

Discussion in 'Digital Photography' started by Paul Ciszek, Nov 18, 2012.

  1. Paul Ciszek

    Paul Ciszek Guest

    For reasons that I will skip in the interests of brevity, I am looking
    for a T-mount adapter for my micro-four-thirds that is shorter than it
    "ought" to be. I see reviewers complaining that this adapter is "too
    deep". Does "too deep" mean "too short"?

    http://www.amazon.com/gp/product/B0036YWB40

    Actually, one reviewer does complain that it is "too long", but I
    find that hard to believe when every other version of the T-mount
    adapter for MFT is much longer, such as this one:

    http://www.amazon.com/Fotodiox-Adapter-T-Mount-Panasonic-AG-AF100/dp/B003EAVUO8

    In short, I want to buy this poorly reviewed item IF the reason that
    it is so poorly reviewed is that the length is too short.


    --
    Please reply to: | No nation is drunken where wine is cheap.
    pciszek at panix dot com | --Thomas Jefferson
    Paul Ciszek, Nov 18, 2012
    #1
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  2. Paul Ciszek

    Martin Brown Guest

    On 18/11/2012 17:07, Paul Ciszek wrote:
    > For reasons that I will skip in the interests of brevity, I am looking
    > for a T-mount adapter for my micro-four-thirds that is shorter than it
    > "ought" to be. I see reviewers complaining that this adapter is "too
    > deep". Does "too deep" mean "too short"?
    >
    > http://www.amazon.com/gp/product/B0036YWB40


    What they appear to mean is that the drift length it adds to the lens
    prevents it from reaching a good focus in the camera. As to whether
    their assessment is correct is anybody's guess. Might be worth
    communicating directly with the owner of the fisheye lens - he may even
    sell you the thing he considers to be defective.
    >
    > Actually, one reviewer does complain that it is "too long", but I
    > find that hard to believe when every other version of the T-mount
    > adapter for MFT is much longer, such as this one:
    >
    > http://www.amazon.com/Fotodiox-Adapter-T-Mount-Panasonic-AG-AF100/dp/B003EAVUO8
    >
    > In short, I want to buy this poorly reviewed item IF the reason that
    > it is so poorly reviewed is that the length is too short.


    Why?

    --
    Regards,
    Martin Brown
    Martin Brown, Nov 18, 2012
    #2
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  3. Paul Ciszek

    Paul Ciszek Guest

    In article <PJ9qs.23688$>,
    Martin Brown <|||newspam|||@nezumi.demon.co.uk> wrote:
    >On 18/11/2012 17:07, Paul Ciszek wrote:
    >>
    >> In short, I want to buy this poorly reviewed item IF the reason that
    >> it is so poorly reviewed is that the length is too short.

    >
    >Why?


    According to my local telescope shop, the only relector telescope
    that you can hook a camera up to is a Cassegrain, because for every
    other design "an SLR can't get close enough". This is a shame,
    because there are some Newtonians that have a focal length in the
    range I am looking for (no more than 1000mm) and a low f number.
    Well, I says to myself, my u4/3 camera is NOT an SLR, and the sensor
    is closer to the great outdoors than on an SLR. If the u4/3 with
    this "too deep" adapter can put the sensor at the focal plane of
    a Newtonian--score!

    --
    Please reply to: | No nation is drunken where wine is cheap.
    pciszek at panix dot com | --Thomas Jefferson
    Paul Ciszek, Nov 18, 2012
    #3
  4. In article <k8ba7t$9m2$>,
    (Paul Ciszek) wrote:

    > In article <PJ9qs.23688$>,
    > Martin Brown <|||newspam|||@nezumi.demon.co.uk> wrote:
    > >On 18/11/2012 17:07, Paul Ciszek wrote:
    > >>
    > >> In short, I want to buy this poorly reviewed item IF the reason that
    > >> it is so poorly reviewed is that the length is too short.

    > >
    > >Why?

    >
    > According to my local telescope shop, the only relector telescope
    > that you can hook a camera up to is a Cassegrain, because for every
    > other design "an SLR can't get close enough". This is a shame,
    > because there are some Newtonians that have a focal length in the
    > range I am looking for (no more than 1000mm) and a low f number.
    > Well, I says to myself, my u4/3 camera is NOT an SLR, and the sensor
    > is closer to the great outdoors than on an SLR. If the u4/3 with
    > this "too deep" adapter can put the sensor at the focal plane of
    > a Newtonian--score!


    Not exactly true.

    http://www.youtube.com/watch?v=cYTmsfpL0M4

    There's also the option to either move the secondary and focuser down
    closer to the primary, or the the primary mirror up the tube closer the
    the focuser.
    Mark Storkamp, Nov 18, 2012
    #4
  5. Paul Ciszek

    Martin Brown Guest

    On 18/11/2012 18:43, Paul Ciszek wrote:
    >
    > In article <PJ9qs.23688$>,
    > Martin Brown <|||newspam|||@nezumi.demon.co.uk> wrote:
    >> On 18/11/2012 17:07, Paul Ciszek wrote:
    >>>
    >>> In short, I want to buy this poorly reviewed item IF the reason that
    >>> it is so poorly reviewed is that the length is too short.

    >>
    >> Why?

    >
    > According to my local telescope shop, the only relector telescope
    > that you can hook a camera up to is a Cassegrain, because for every
    > other design "an SLR can't get close enough". This is a shame,


    It is also not true provided that you choose wisely. I have taken plenty
    of photographs using a Newtonian f5 scope with an SLR. It all depends on
    how much back focus the scope permits.

    SCTs have enormous back focus range which allows a lot more latitude but
    some Newtonian reflectors can be used with 35mm cameras.

    > because there are some Newtonians that have a focal length in the
    > range I am looking for (no more than 1000mm) and a low f number.
    > Well, I says to myself, my u4/3 camera is NOT an SLR, and the sensor
    > is closer to the great outdoors than on an SLR. If the u4/3 with
    > this "too deep" adapter can put the sensor at the focal plane of
    > a Newtonian--score!


    You should be bale to measure where the focal plane actually is and then
    do the sums. Even if you can't do it as you would like afocal
    photography looking into a eyepiece and focussed at infinity will work.

    --
    Regards,
    Martin Brown
    Martin Brown, Nov 18, 2012
    #5
  6. Paul Ciszek

    Paul Ciszek Guest

    In article <PJ9qs.23688$>,
    Martin Brown <|||newspam|||@nezumi.demon.co.uk> wrote:
    >On 18/11/2012 17:07, Paul Ciszek wrote:
    >> For reasons that I will skip in the interests of brevity, I am looking
    >> for a T-mount adapter for my micro-four-thirds that is shorter than it
    >> "ought" to be. I see reviewers complaining that this adapter is "too
    >> deep". Does "too deep" mean "too short"?
    >>
    >> http://www.amazon.com/gp/product/B0036YWB40

    >
    >What they appear to mean is that the drift length it adds to the lens
    >prevents it from reaching a good focus in the camera. As to whether


    What does this mean in layman's terms? Is the adapter too short, bringing
    the camera too close to what it is attached to?

    --
    "Remember when teachers, public employees, Planned Parenthood, NPR and PBS
    crashed the stock market, wiped out half of our 401Ks, took trillions in
    TARP money, spilled oil in the Gulf of Mexico, gave themselves billions in
    bonuses, and paid no taxes? Yeah, me neither."
    Paul Ciszek, Nov 20, 2012
    #6
  7. Paul Ciszek

    Martin Brown Guest

    On 20/11/2012 05:11, Paul Ciszek wrote:
    > In article <PJ9qs.23688$>,
    > Martin Brown <|||newspam|||@nezumi.demon.co.uk> wrote:
    >> On 18/11/2012 17:07, Paul Ciszek wrote:
    >>> For reasons that I will skip in the interests of brevity, I am looking
    >>> for a T-mount adapter for my micro-four-thirds that is shorter than it
    >>> "ought" to be. I see reviewers complaining that this adapter is "too
    >>> deep". Does "too deep" mean "too short"?
    >>>
    >>> http://www.amazon.com/gp/product/B0036YWB40

    >>
    >> What they appear to mean is that the drift length it adds to the lens
    >> prevents it from reaching a good focus in the camera. As to whether

    >
    > What does this mean in layman's terms? Is the adapter too short, bringing
    > the camera too close to what it is attached to?


    Possibly. It is impossible to tell for certain what they mean.

    But if the film plane is physically too close to the lens there will
    never be any object distance where an image can be made in focus.

    If it is too far away then for a sufficiently close in object an in
    focus image can be formed at the film plane but objects at infinity (or
    beyond some fixed distance will be forever out of focus).

    What I suggest you do it get the moon in the scope and use a piece of
    tracing paper to find out where the prime focus plane is in relation to
    the eyepiece focusser mount. This will give you some idea how much
    distance you have to play with. Small Newtonians tend not to have a lot
    of back focus although you might be able to engineer some more at the
    expense of a higher magnification by using a Barlow lens.

    --
    Regards,
    Martin Brown
    Martin Brown, Nov 20, 2012
    #7
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