Thanks Kalon.
I think one of the big challenges in camera trapping is trying to plan a shot when you don't know how much ambient light there will be; I went down a rabbit hole trying to use ttl flash and camera metering, but it's never worked. I shy away away from intentional daytime shots because the limitations of camera x-synch speeds. Unless I'm in heavy shade, I have to set ~ ISO 200, f11 to not overexpose at 1/200s, then my flashes have to be at 1/2-1/1 power (especially since most waterproofing seems to steal about a stop of light) and fairly close and I'm left with limited options for lighting and the downsides of high power flash (loud, drains battery, can overheat flash, motion blur for small fast critters). I'd be OK with all that if I got more triggers during the day and in certain situations I do, but in this case I figured I'd go with a night shot cause the nights are long and I guessed that carnivores would be more nocturnal here because they get a fair bit of hunting pressure (had hounds tree a cat next to me last year while scouting a site)
I think the hardest thing is to set for a twilight shot -- if you go for night stars you're gonna blow out that beautiful blue hour shot just before/after sunset. I've tried to target this time of day using aperture-priority metering, but if you get a critter in the frame the camera often meters a really long exposure (even if you dial in exposure compensation), so you get a blown out sky and a motion blurred critter, even at like -2ev exp. comp. I've had Av mode work OK sometimes, but got burned bad too. Had a black bear sow and YOY cubs fill the whole frame and then blur out cause of a 6s exposure or something like that.
Cause of all this, I usually just risk it and go for the full darkness long exposure. This is crazy too though because of subtle differences in light levels. The safest bet is to shoot in a closed canopy forest so you know your critter will be in the shade, then you can burn in the sky only. I shot a gray fox under a supermoon in a conifer forest (in a canyon) and was OK even at like ISO 3200, f8 30s, the sky looked like daytime but fox was sharp and in the shade. But I blew it bad a month ago and got several big mystery critters in the snow under a full moon, tortured by those, can just barely make out areas where show up in front of dark tree trunks but otherwise they are see through.
In my experience, setting long exposures greatly reduces odds of success, brings up like 3 more damn things that have to go right, plus you only get one shot so if the flashes don't wake or the position is bad, you're done. However, if I'm targeting a critter that I've already gotten a good shot of; I'm willing to take some pretty bad odds for the opportunity to get something new.
Also, I find that the surprise and uncertainty of long exposures is pretty thrilling; same sort of thrill for me as not knowing what animal you'll get. Once I set with a cascade volcano in the background and in the long exposure it was ringed in fire by controlled burns -- there was no critter in the shot, but it's those sort of surprises that keep me hooked.
I use a full frame camera usually for high ISO stuff, but I did some with a D3200, and with my old 7D I've shot a lot of underwater shots at 1600 and printed them, so I think it's OK wth a crop sensor too, particularly the newer ones. Plus with moonlight you can probably go ISO 800 30s f8 and get lots of ambient.
One other strategy I do is zero ambient, but still high ISO to get flash power so I can light large areas with a speedlight. In these instances, it's not that I want to make everything bright and lose the sense of night, but I want to cast a low level of light evenly.
Hope that helps. Good luck this winter!
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