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  1. #1

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    Ektar lens spectral transmission chart

    Does anyone have, or know where one can obtain a spectral transmission chart for Ektar lenses? Specifically the 63mm, 102mm and 152mm lens. This would be from the late 1940's and 1950's.

  2. #2
    AgX
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    I don't expect the transmission of lenses above the UV region to vary substantially.

  3. #3
    Mustafa Umut Sarac's Avatar
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    But Color MTF graph vary very much but they are for infinity and I found only once or twice.
    Last edited by Mustafa Umut Sarac; 04-26-2014 at 01:51 PM. Click to view previous post history.
    Can you please ask easier questions ? One Apug members request .

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    example chart

    I've uploaded a screen shot from a document that shows 3 lenses. So I'm looking for the same info on 102mm and 152mm lens. BTW, any thoughts on why the 63mm 2 would be so far off transmission-wise to the 2.7 lens?
    Thanks,
    Pete
    Attached Thumbnails Attached Thumbnails Screen Shot 2014-04-26 at 12.47.40 PM.png  

  5. #5
    AgX
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    Quote Originally Posted by Mustafa Umut Sarac View Post
    But Color MTF graph vary very much but they are for infinity and I found only once or twice.
    An MTF refers to image quality (resolution vs. contrast).
    The topic of this thread is spectral transmission.

  6. #6
    AgX
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    Quote Originally Posted by vceinc01 View Post
    BTW, any thoughts on why the 63mm 2 would be so far off transmission-wise to the 2.7 lens?
    The graphic is misleading at first sight. So it is 85% vs. 65%

    I assume the reason to be strong complementary colour casts of different elements. Resulting in a still neutral but darker image.



    As comparison charts of modern photographic lenses:
    http://spectroscopy.wordpress.com/20...00mm-f2-8l-ii/

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    transmission

    Thank you for this link to the Canon lenses. This makes sense to me that there would be greater transmission with an 2 than with an 2.8 lens, or is that wrong? The chart I uploaded seems to indicate less transmission with the 63mm 2 lens vs the 63mm 2.7. Does that make sense?

  8. #8
    AgX
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    You mix up things:

    -) the absolute amount of light going through a F 2.0 lens is of course larger than that of F 2.8 lens (granted identical sorts of glass and the same even light sorce covering the lenses)

    -) the relative amount of light (based on useful flux going through the front lens, as I understand transmission in this case) is identical with both lenses (again granted identical sorts of glass )


    -) the relative amount of light would of course be different if glasses with different scpectral or neutral density or different coatings are used.

  9. #9
    AgX
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    As you see in the modern Canon charts the difference between the two lenses is about 10%points at maximum, whereas the speed of lenses varies by factor 2.
    "Transmission" thus is used the way I did above.

    In general transmission refers to the ratio between in/out. If more goes in (larger front lens diameter), more should come out, the ratio being unchanged.



    So, basically from what goes in 85-95% must come out in modern lenses with few and coated elements.
    Last edited by AgX; 04-27-2014 at 09:12 AM. Click to view previous post history.

  10. #10

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    transmission

    Thanks AgX,

    So the chart that I put up probably indicates the the 63mm 2 lens is a much older lens with inferior coatings? The 2.7 63mm lens is an improvement but the chart you posted shows the most modern lens transmission improvements over the better 63mm 2.7 lens. Is there a way to establish the transmission differences in terms of ND or /stops?

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