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Thread: What is the meaning of the red words?

  1. #1
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    Default What is the meaning of the red words?

    on the focus distance window of these two lenses there are additional red etchings indicating different focal lengths. how is one supposed to read the scales?




    thanx in advance!

  2. #2

    Default Re: what is the meaning of the red words?

    White line - the focus distance of the lens. If it points to the white "5", it means the lens is focused at 5m away.

    The red lines indicate the depth of field at the various focal lengths. For example, if it points at "5", and your lens is at 70mm focal length, that means that anything between 5-10m is "in focus". If you lens is at 135mm focal length, it means the DOF extends from 5m to ~7-8m. The short line beside the "135" mark is probably for the 100mm focal length (not enough space to engrave it on the lens, I suppose).

    I'm assuming that the engravings for the DOF are marked at the lens' largest aperture.

    Same thing for your 80mm lens.


    EDIT: Nope, it's not DOF scales (as the later posts shows). For IR film focus shift instead.
    DOF scales are marked both sides of the focusing scale for all the different apertures, usually on prime lenses. Got mixed up.
    Last edited by Ah Pao; 5th May 2006 at 10:33 AM.

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    Default Re: what is the meaning of the red words?

    ah! so it is the DOF scales. thanx so much. strange the 80-200mm only show DOF for 80mm.

  4. #4

    Default Re: what is the meaning of the red words?

    I suspect for your 80-200mm lens, the DOF at 200mm is so shallow that it will be around the same point as your focus distance.

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    Default Re: what is the meaning of the red words?

    Quote Originally Posted by Ah Pao
    White line - the focus distance of the lens. If it points to the white "5", it means the lens is focused at 5m away.

    The red lines indicate the depth of field at the various focal lengths. For example, if it points at "5", and your lens is at 70mm focal length, that means that anything between 5-10m is "in focus". If you lens is at 135mm focal length, it means the DOF extends from 5m to ~7-8m. The short line beside the "135" mark is probably for the 100mm focal length (not enough space to engrave it on the lens, I suppose).

    I'm assuming that the engravings for the DOF are marked at the lens' largest aperture.

    Same thing for your 80mm lens.
    DOF at which Aperture? And usually DOF put a scale with white colour at nearer and farther distance. This one only at farther distance.

    I am not sure about this, but last time I know the red colour indicate focus distance for InfraRed Photography.

    Regards,
    Arto.

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    Default Re: what is the meaning of the red words?

    mmm… anyone has a manual of that 28-135mm lens to refer?

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    Default Re: what is the meaning of the red words?

    Quote Originally Posted by Ah Pao
    I'm assuming that the engravings for the DOF are marked at the lens' largest aperture.
    Ups..., I didn't see your mention about the largest aperture.... .

    Regards,
    Arto.

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    Moderator catchlights's Avatar
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    Default Re: what is the meaning of the red words?

    is for compensation of Infrared Wavelength Focusing when doing Infrared Photography

    if it is for DOF indication, should be indicate f-stop, not focal length.

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    Default Re: what is the meaning of the red words?

    mmm… not tremendously useful for me then (IR I mean).

    for a zoom lens, DOF indication would require focal length as well right?

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    Default Re: what is the meaning of the red words?

    Quote Originally Posted by hwchoy
    mmm… not tremendously useful for me then (IR I mean).

    for a zoom lens, DOF indication would require focal length as well right?
    and Aperture as well...

    Regards,
    Arto.

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    Default Re: what is the meaning of the red words?

    Quote Originally Posted by Artosoft
    and Aperture as well...

    Regards,
    Arto.
    yes, or assuming widest aperture as postulated by Ah Pao.

  12. #12
    Moderator catchlights's Avatar
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    Default Re: what is the meaning of the red words?

    if it is for DOF, why is on one side only and not both side?

    best is you check on the lens manual.

  13. #13

    Default Re: what is the meaning of the red words?

    Quote Originally Posted by catchlights
    is for compensation of Infrared Wavelength Focusing when doing Infrared Photography

    if it is for DOF indication, should be indicate f-stop, not focal length.
    From the scale, it looks more like DoF. If it were for infrared focus, it would not shift so much more the wider you go. Plus, if the 80-200 is APO, then there shouldn't be another focus for IR.

  14. #14

    Default Re: what is the meaning of the red words?

    Quote Originally Posted by catchlights
    if it is for DOF, why is on one side only and not both side?

    best is you check on the lens manual.
    More like for indicating the hyperfocal distance I presume. I'm not a Canon user..

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    Default Re: what is the meaning of the red words?

    Quote Originally Posted by lsisaxon
    More like for indicating the hyperfocal distance I presume. I'm not a Canon user..
    Hyperfocal distance need aperture value also.

    Hmmm.... must do RTFM. I am also non CANON user.

    Regards,
    Arto.
    Last edited by Artosoft; 3rd May 2006 at 09:32 AM.

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    Default Re: what is the meaning of the red words?

    DOF scale is explained here

    http://jimdoty.com/Tips/Depth_of_Fie..._of_field.html

    pictures as well

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    Default Re: what is the meaning of the red words?

    Quote Originally Posted by lsisaxon
    From the scale, it looks more like DoF. If it were for infrared focus, it would not shift so much more the wider you go. Plus, if the 80-200 is APO, then there shouldn't be another focus for IR.
    Are you sure? If I am not wrong, the wider, the more Ir focus shift.

    Regards,
    Arto.

  18. #18
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    Default Re: what is the meaning of the red words?

    I bought all my lenses second hand, no manual leh.

    what do you mean "if the 80-200 is APO" ?

  19. #19
    Moderator catchlights's Avatar
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    Default Re: what is the meaning of the red words?

    Quote Originally Posted by lsisaxon
    More like for indicating the hyperfocal distance I presume. I'm not a Canon user..
    I agreed with you of both, it looks strange to me as a IR indication mark, normally is only 0.25% shift, it wouldn't be that much.

    I'm not a canon user too, don't have a manual to check out.

  20. #20

    Default Re: what is the meaning of the red words?

    Quote Originally Posted by Artosoft
    Are you sure? If I am not wrong, the wider, the more Ir focus shift.

    Regards,
    Arto.
    I think you are right. Doesn't quite make sense for the DoF to be marked this way and yes, IR would have shifted more the wider you go because of the shorter focal length.

    Edited: Checked with a Canon user. It's for IR.
    Last edited by lsisaxon; 3rd May 2006 at 09:46 AM.

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