AAK. For your 1774 Vs 1758 chapter.

Started May 17, 2007 | Discussions thread
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tyampel
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AAK. For your 1774 Vs 1758 chapter.
May 17, 2007

Alan.

You mentioned that the 1774 lens brings more light being larger.
So I did some measuring and made some calculation.

The diameter of the glass portion of the outer native lens on the H5 is 33mm. On the H9 it is 37mm.

The diameter of the bottom lens of the DH1758 is 35mm.

Projecting a 35 mm circle onto the 37mm lens of the H9 will result in an area loss of 11%, the are of a circle being proportional to the square value of the diameter. 35*35 / 37*37 = 0.89.

However the whole circle of the projected area is not used by the camera as the sensor is a 3x4 rectangle. We have proof of this in seeing the effects of improperly installed lens hood, where the petal's shadow is visible.

So taking that into effect, my estimate is that the loss is closer to 5%.

The camera's metering system should not even pick it up when set to Center Or Spot metering.

Can you, please, confirm this when doing experiments with both TC adapters - 1774 and 1758.

Thanks and good luck.

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Tod Yampel

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