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03-10-2011, 05:04 AM   #1
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DA 35 f/2.4 T-stop?

I'm sorry to bring up an old discussion, but I am a little curious...

Does anyone know the T-stop value of the DA 35 f/2.4? I was comparing it to the Nikkor 35 f/1.8, and realized that 8-element lens actually has a T-stop (light transmission capability) of T/2.2, while the DA 35 f/2.4 has six elements, so according to my understanding it should have better transmission characteristics. My theory is that the difference in shutter speed at the same aperture between these two lenses should be absolutely negligible.

03-10-2011, 05:59 AM   #2
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The number of elements has some impact (more accurately, the numberr of interfaces) but the density of the glass, the thickness of it, will also have a strong impact.

But this measurement is not really useful for photography because differences are marginal when compared to the effect of the focal length and aperture.
03-10-2011, 07:09 AM   #3
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What is important is that the 35 2.4 exposes brighter than your average lens at 2.4.

You lose DOF control, but you don't really lose that much light, compared with the FA 35 2.0.
03-10-2011, 07:35 AM   #4
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Going to use this thread for another thing, too:

My DA40 seems to consistently give the exact same shutter speeds and exposure whether I set aperture to 2.8 or 3.2. What's up?

03-10-2011, 07:57 AM   #5
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because there is only 1/3 stop between f2.8 et f3.2, so if you set incremental at 1/2 stop instead of 1/3 stop, the body won't do anything. if you go from 2.8 to 3.5 (so decrease exposure of 2/3 stop), the body will do some change.

am i clear ? i'm not really sure ...

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