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09-21-2011, 05:09 AM   #1
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TAv Mode and DA* 16-50mm

I've discovered that when using my K5 -w- my new DA* 16-50mm lens in TAv mode, the ISO setting will vary when zooming, even though the lens is a constant f2.8. Isn't the whole purpose of a constant aperture lens to avoid this? It seems the ISO should stay constant in this condition, or am I missing something?


09-21-2011, 05:39 AM   #2
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I would think that, unless you are pointing it at a white wall, the scene will be changing as you zoom and the metering will need to change the ISO to adjust the exposure. I suppose that if you were using spot metering that the ISO would be more likely to remain constant as you zoom.
09-21-2011, 05:41 AM   #3
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I think the metering is affecting the ISO. When you zoom in and out the camera meters differently as the scene changes. Try spot metering and zooming in and out. It should not change then.

Edit: oops I was beaten to it
09-21-2011, 06:35 AM   #4
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Zooming and panning are similar in changing the metering.......Tav is my most used mode, I don't worry much about the ISO, but then again, I am not as particular on the results as some. If I get a Squirrel, I'm happy!


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