We may as well put the graphical comparison for the same test from that thread here.
Left the original halogen, right the replacement HID, without realignment.
Check the alignment when you've replaced a light...!
If you don't, and it is out, and you don't correct for it, you may blind other traffic (and fail govt tests).
Of course, when the light source is misplaced in the lamp, or wider than the lamp housing design accounts for, that may cause trouble.
In the case of HIDs their 3x brightness would cause the stray light to be 3 times as bright too, even if the discharge area would align perfectly with the hottest part of the halogen filament.
Measures to reduce that stray light (caps, specially designed reflectors or projectors) might be necessary.
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2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut.
lifetime FE over 0.2 Gmeter or 0.13 Mmile.
For confirmation go to people just like you.
For education go to people unlike yourself.