Ektar lens spectral transmission chart

vceinc01

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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.
 

AgX

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

Mustafa Umut Sarac

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But Color MTF graph vary very much but they are for infinity and I found only once or twice.
 
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vceinc01

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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 ƒ2 would be so far off transmission-wise to the ƒ2.7 lens?
Thanks,
Pete
 

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AgX

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vceinc01

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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 ƒ2 than with an ƒ2.8 lens, or is that wrong? The chart I uploaded seems to indicate less transmission with the 63mm ƒ2 lens vs the 63mm ƒ2.7. Does that make sense?
 

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.
 

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.
 
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vceinc01

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transmission

Thanks AgX,

So the chart that I put up probably indicates the the 63mm ƒ2 lens is a much older lens with inferior coatings? The ƒ2.7 63mm lens is an improvement but the chart you posted shows the most modern lens transmission improvements over the better 63mm ƒ2.7 lens. Is there a way to establish the transmission differences in terms of ND or ƒ/stops?
 

AgX

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Maybe a missing coating. Maybe elements with neutralizing colour hue, as I refered to above.
We got some old-lens experts here. They would know better.


A reduction in transmission from 85% to 65% as in your Ektar chart would be 1/2 stop.
 

AgX

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The transmission of lenses is the topic of this thread.
And this is dependant on the characteristic of the medium (typically optical glasses), but also on a anti-reflection coating employed.
 
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