The thing is to position the glasses so that the angle is such that the light reflects harmlessly off into space. Doesn’t really matter where.

这变成了:

“你需要做的是掌控光线从眼镜反射回来的角度，让它反射到相机以外的任何地方”

上面的例子里reflect变成反射了

另外一个：

If you already know how to do a portrait without having to worry about reflections in peoples’ glasses, just scroll down to the bottom and move on.

这变成了:

“如果你在拍摄头像照时已经有了对付眼镜倒影的方法，请跳过本篇内容，继续浏览闪卓博识网站的其他文章”

这里是倒影的意思，具体是光源的倒影。其实实际上“倒影”都是反光的效果，如果光源的光线要从镜片反光到你的眼球，你就会看到它的倒影

不过个人理解在这里作“反光”讲似乎更讲得通一些，尤其前面《跟眼镜打光的技巧》那篇，根据上下文看，如何调整角度以避免镜片的反光，“倒影”的话倒似乎不大好理解了。

“A blinding reflection from the glass windows across the way made it difficult to concentrate”

另外一个意思是倒影：

“When I looked in the lake, I saw my reflection, but couldn’t believe how old I looked”

有一点翻译的问题供参考：
relection应该是指反光，前面一篇讲拍摄戴眼镜的也是。