General Lens ZOOM question....

Discussion in 'Digital Photography' started by advid, Jun 25, 2004.

  1. advid

    advid Guest

    .... I've got a Canon D30 and a Canon 300D that my wife and I enjoy
    using for mainly birds/wildlife....

    We've been using a Canon 75-300 usm (sometimes with a 1.4 extender)
    for close ups of birds etc...

    I've just got a Tamron 28-300 XR and at full 300mm it gets nowhere
    near as close as the Canon at 300mm.... Even with the 1.4 on it's only
    just about the same as the Canon wothout the 1.4 on - why should there
    be such a difference ????

    Surely 300mm is 300mm no matter what make of lens..... ?
    advid, Jun 25, 2004
    #1
    1. Advertising

  2. advid

    leo Guest

    "advid" <> wrote in message
    news:...
    > ... I've got a Canon D30 and a Canon 300D that my wife and I enjoy
    > using for mainly birds/wildlife....
    >
    > We've been using a Canon 75-300 usm (sometimes with a 1.4 extender)
    > for close ups of birds etc...
    >
    > I've just got a Tamron 28-300 XR and at full 300mm it gets nowhere
    > near as close as the Canon at 300mm.... Even with the 1.4 on it's only
    > just about the same as the Canon wothout the 1.4 on - why should there
    > be such a difference ????
    >
    > Surely 300mm is 300mm no matter what make of lens..... ?



    I can't answer you what makes the difference bettween lenses. I just sold my
    Canon 75-300 IS lens ($400) and replaced it with 300mm f/4 IS prime lens
    ($1100). I compare the picture quality of the same images I took at 300mm.
    The advantage of a good prime lens is not only the sharpness but the color
    and contrast are much, much better.
    leo, Jun 25, 2004
    #2
    1. Advertising

  3. advid

    Jeff Durham Guest

    That is an interesting observation. I too thought 300 was 300 per my
    observations. I had a ~270mm telephoto on an old 35mm. I compared what I
    saw with my Rebel using 270mm factoring in the 1.6X conversion number for
    35mm and the picture information was darn near identical. That old lens was
    more than twice the size so I was really curious if they would be the same.
    I also compared my Kodak P&S digital to my Rebel and found similar results.

    Maybe some of the experts in this group can explain what you are seeing.

    Jeff


    "advid" <> wrote in message
    news:...
    > ... I've got a Canon D30 and a Canon 300D that my wife and I enjoy
    > using for mainly birds/wildlife....
    >
    > We've been using a Canon 75-300 usm (sometimes with a 1.4 extender)
    > for close ups of birds etc...
    >
    > I've just got a Tamron 28-300 XR and at full 300mm it gets nowhere
    > near as close as the Canon at 300mm.... Even with the 1.4 on it's only
    > just about the same as the Canon wothout the 1.4 on - why should there
    > be such a difference ????
    >
    > Surely 300mm is 300mm no matter what make of lens..... ?
    Jeff Durham, Jun 25, 2004
    #3
  4. advid

    leo Guest

    "Jeff Durham" <> wrote in message
    news:gAXCc.158680$...
    > That is an interesting observation. I too thought 300 was 300 per my
    > observations. I had a ~270mm telephoto on an old 35mm. I compared what I
    > saw with my Rebel using 270mm factoring in the 1.6X conversion number for
    > 35mm and the picture information was darn near identical. That old lens

    was
    > more than twice the size so I was really curious if they would be the

    same.
    > I also compared my Kodak P&S digital to my Rebel and found similar

    results.
    >
    > Maybe some of the experts in this group can explain what you are seeing.
    >
    > Jeff
    >
    >
    > "advid" <> wrote in message
    > news:...
    > > ... I've got a Canon D30 and a Canon 300D that my wife and I enjoy
    > > using for mainly birds/wildlife....
    > >
    > > We've been using a Canon 75-300 usm (sometimes with a 1.4 extender)
    > > for close ups of birds etc...
    > >
    > > I've just got a Tamron 28-300 XR and at full 300mm it gets nowhere
    > > near as close as the Canon at 300mm.... Even with the 1.4 on it's only
    > > just about the same as the Canon wothout the 1.4 on - why should there
    > > be such a difference ????
    > >
    > > Surely 300mm is 300mm no matter what make of lens..... ?


    I misread the question. The focal length are not exactly the same. My new
    300mm f/4 IS is slightly longer than the 75-300mm IS at 300mm. Only very
    slightly though. If the difference is huge, somebody's cheating...
    leo, Jun 25, 2004
    #4
  5. advid

    George Guest

    As you may have guessed, there is some "rounding" (by marketing) of the
    actual focal length on virtually all lenses. I believe the industry allows
    about 5%...I don't believe that it is a deliberate attempt to mislead, more
    likely a convenience (to the customer) for comparison and remembering the
    lens. Sounds like your Tamron is rounded "up" on the high end while your
    Canon may be rounded "down" a bit. But, I wouldn't expect it to be so
    noticeable unless your subject to camera distance is changing as well and
    one lens focuses closer as well (from your comments, that would likely be
    the Canon).

    "advid" <> wrote in message
    news:...
    > ... I've got a Canon D30 and a Canon 300D that my wife and I enjoy
    > using for mainly birds/wildlife....
    >
    > We've been using a Canon 75-300 usm (sometimes with a 1.4 extender)
    > for close ups of birds etc...
    >
    > I've just got a Tamron 28-300 XR and at full 300mm it gets nowhere
    > near as close as the Canon at 300mm.... Even with the 1.4 on it's only
    > just about the same as the Canon wothout the 1.4 on - why should there
    > be such a difference ????
    >
    > Surely 300mm is 300mm no matter what make of lens..... ?
    George, Jun 25, 2004
    #5
  6. advid

    Tony Spadaro Guest

    In general there is a 10% fudge factor on lenses. (ie anything between
    270 and 330 would be a 300, but believe me now one ever called a 325mm lens
    300. It could be that for these "super" zooms, a lot of the range has more
    to do with advertising than fact. I would say that if you need a 1.4 TC to
    get 300mms out of it, it's a good lens to send back.

    --
    http://www.chapelhillnoir.com
    home of The Camera-ist's Manifesto
    The Improved Links Pages are at
    http://www.chapelhillnoir.com/links/mlinks00.html
    A sample chapter from my novel "Haight-Ashbury" is at
    http://www.chapelhillnoir.com/writ/hait/hatitl.html
    "advid" <> wrote in message
    news:...
    > ... I've got a Canon D30 and a Canon 300D that my wife and I enjoy
    > using for mainly birds/wildlife....
    >
    > We've been using a Canon 75-300 usm (sometimes with a 1.4 extender)
    > for close ups of birds etc...
    >
    > I've just got a Tamron 28-300 XR and at full 300mm it gets nowhere
    > near as close as the Canon at 300mm.... Even with the 1.4 on it's only
    > just about the same as the Canon wothout the 1.4 on - why should there
    > be such a difference ????
    >
    > Surely 300mm is 300mm no matter what make of lens..... ?
    Tony Spadaro, Jun 26, 2004
    #6
  7. "Tony Spadaro" <> wrote in message news:<Iv5Dc.74672$>...

    > In general there is a 10% fudge factor on lenses. (ie anything between
    > 270 and 330 would be a 300, but believe me now one ever called a 325mm lens
    > 300. It could be that for these "super" zooms, a lot of the range has more
    > to do with advertising than fact. I would say that if you need a 1.4 TC to
    > get 300mms out of it, it's a good lens to send back.


    > > Surely 300mm is 300mm no matter what make of lens..... ?


    You will find that the Sigma lenses are the most accurate in terms of
    focal length accuracy. I conducted some very thorough testing in this
    area last year. My photography students learned quite a bit from the
    study. Unfortunately, my sponsors prevented me from publishing the
    results due to corporate politics.
    Giorgio Preddio, Jun 26, 2004
    #7
  8. In article <>, Giorgio
    Preddio <> wrote:

    > You will find that the Sigma lenses are the most accurate in terms of
    > focal length accuracy. I conducted some very thorough testing in this
    > area last year. My photography students learned quite a bit from the
    > study. Unfortunately, my sponsors prevented me from publishing the
    > results due to corporate politics.


    Put down the crack pipe, George.
    Randall Ainsworth, Jun 26, 2004
    #8
  9. advid

    Guest

    In message <>,
    (Giorgio Preddio) wrote:

    >My photography students learned quite a bit


    Did you ask the toddlers if they really wanted the lessons?
    --

    <>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
    John P Sheehy <>
    ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
    , Jun 26, 2004
    #9
  10. (advid) writes:

    >Surely 300mm is 300mm no matter what make of lens..... ?


    It is. At most one of the lenses is marked accurately.
    Why not measure the actual lens focal length yourself?

    All you need is a pair of objects with clear edges a measured distance
    apart. Shoot them from a long way away so both are visible, and the
    distance between them is (say) 1/10 to 1/4 of the image width. Then
    look at the digital image and determine the distance between the two
    objects in pixels.

    The distance in pixels multiplied by the pixel pitch of your camera's
    sensor tells you the image distance between the two objects. You
    already measured the distance between the real objects. Now measure the
    distance from the front of the camera lens to the real objects. Given
    these three pieces of information, plug them into one of the standard
    lens formulas and solve for the lens focal length.

    Done carefully, this is very accurate. The focal length of a lens is
    *defined* by its on-axis magnification.

    Dave
    Dave Martindale, Jun 26, 2004
    #10
  11. On 26 Jun 2004 07:29:36 -0700, (Giorgio
    Preddio) wrote:

    >"Tony Spadaro" <> wrote in message news:<Iv5Dc.74672$>...
    >
    >> In general there is a 10% fudge factor on lenses. (ie anything between
    >> 270 and 330 would be a 300, but believe me now one ever called a 325mm lens
    >> 300. It could be that for these "super" zooms, a lot of the range has more
    >> to do with advertising than fact. I would say that if you need a 1.4 TC to
    >> get 300mms out of it, it's a good lens to send back.

    >
    >> > Surely 300mm is 300mm no matter what make of lens..... ?

    >
    >You will find that the Sigma lenses are the most accurate in terms of
    >focal length accuracy. I conducted some very thorough testing in this
    >area last year. My photography students learned quite a bit from the
    >study. Unfortunately, my sponsors prevented me from publishing the
    >results due to corporate politics.



    Hogwash.


    GK
    grant kinsley, Jun 26, 2004
    #11
  12. advid

    Tony Spadaro Guest

    George is, of course, lying. He owns no camera, has no students, has never
    tested anything, and is full of shirt.

    --
    http://www.chapelhillnoir.com
    home of The Camera-ist's Manifesto
    The Improved Links Pages are at
    http://www.chapelhillnoir.com/links/mlinks00.html
    A sample chapter from my novel "Haight-Ashbury" is at
    http://www.chapelhillnoir.com/writ/hait/hatitl.html
    "Giorgio Preddio" <> wrote in message
    news:...
    > "Tony Spadaro" <> wrote in message

    news:<Iv5Dc.74672$>...
    >
    > > In general there is a 10% fudge factor on lenses. (ie anything between
    > > 270 and 330 would be a 300, but believe me now one ever called a 325mm

    lens
    > > 300. It could be that for these "super" zooms, a lot of the range has

    more
    > > to do with advertising than fact. I would say that if you need a 1.4 TC

    to
    > > get 300mms out of it, it's a good lens to send back.

    >
    > > > Surely 300mm is 300mm no matter what make of lens..... ?

    >
    > You will find that the Sigma lenses are the most accurate in terms of
    > focal length accuracy. I conducted some very thorough testing in this
    > area last year. My photography students learned quite a bit from the
    > study. Unfortunately, my sponsors prevented me from publishing the
    > results due to corporate politics.
    Tony Spadaro, Jun 30, 2004
    #12
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Ronny Svensson

    Re: Difference between C-40 zoom [D-40 zoom] and c-4000 zoom

    Ronny Svensson, Aug 23, 2003, in forum: Digital Photography
    Replies:
    0
    Views:
    918
    Ronny Svensson
    Aug 23, 2003
  2. Stefan Patric

    Re: Difference between C-40 zoom [D-40 zoom] and c-4000 zoom

    Stefan Patric, Aug 23, 2003, in forum: Digital Photography
    Replies:
    0
    Views:
    771
    Stefan Patric
    Aug 23, 2003
  3. klausa
    Replies:
    9
    Views:
    415
    Nostrobino
    Jul 30, 2005
  4. Teamhair

    Olympus D-550 Zoom problems with zoom lens

    Teamhair, Aug 20, 2006, in forum: Digital Photography
    Replies:
    0
    Views:
    370
    Teamhair
    Aug 20, 2006
  5. asdf3b

    Traveling with DSLR & prime lens [non-zoom lens]

    asdf3b, Dec 17, 2007, in forum: Digital Photography
    Replies:
    4
    Views:
    843
Loading...

Share This Page