If all else was equal the 5 element would be a little bit brighter but
not enough to notice. Say each element transmits 980f the light
passing through. Then the fraction of light making it right through to
the back is 0.98 raised to the power of the number of elements: 0.87 for
7 elements and 0.90 for 5 elements. So the 5 element only lets in 4%
more light than the 7 element - definitely too small to be noticable in
the viewfinder.
Roger
> Here lies my confusion. I have a 5 element and a 7 element doubler. When
> taking the same picture with each doubler, I would expect the 5 element to
> be a bit brighter (less glass?). Yet they are pretty much the same to my
> eye.
>
> Thanks.
>
> John Cwiklinski
>
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