Also... I'd argue that there's a bigger deal being made about reciprocity than is really necessary. I'm not saying it's not a thing. But at relatively short exposure times (like 10 seconds), I don't know that it's as much a concern as it would be at longer exposures (like 1-5 minutes). When I've shot at night with over-exposed film (I always shoot CineStill 800T at night rated at 400), I've never even compensated for reciprocity and my stuff turns out fine. For your night stuff, I'd shoot at one stop over-exposed (set your ISO in your camera or hand-held meter or phone meter or whatever to 200 if you're shooting Portra 400) and then shoot at whatever shutter speed it tells you. If it's more than like 30 seconds, maybe add a stop by opening up your aperture one click or throw in another 15 seconds or whatever, but since you're already over-exposing by a stop, you're kind of accounting for reciprocity in that adjusted exposure calculation.