77mm 1.8 Limited - AF speed on K30 (or K5) in low light?

I find the 77 to be significantly faster to focus on the K-30 than it was on my K-r. I'm actually pretty surprised by the difference. In low light, it's not as fast but still not bad. I really don't know how much faster it could be in low light. That's a challenging situation. The DA*55 is hideously slow in low light.

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