〜ところを見ると
judging from (the fact that)
Plain form + ところを見ると / ところからすると
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ところを見ると draws a conclusion from what you can observe: 笑っているところを見ると、試験はうまくいったようだ, "judging from the fact that he's smiling, the exam must have gone well".
The first half is a visible fact, and the second half is a guess, so it almost always ends with ようだ, らしい, のだろう or に違いない.
It's close to から判断すると and からすると (N2), but ところを見ると focuses on a specific, observed situation right in front of you. It pairs naturally with とみえる (N1).
Don't confuse it with ところに (N2), "just then", which is about timing.
Examples
笑っているところを見ると、試験はうまくいったようだ。
Judging from the fact that he's smiling, the exam must have gone well.
返事がないところを見ると、留守らしい。
There's no answer, so they must be out.
何も言わないところを見ると、彼は反対ではないのだろう。
Since he isn't saying anything, he probably isn't against it.
あわてているところを見ると、何かあったに違いない。
Judging by how flustered she is, something must have happened.
行列ができているところを見ると、人気の店なのだろう。
Seeing the queue, it must be a popular place.