> On a side note I sometimes wonder if other animals have a quicker “refresh rate” on their eyes.
Indeed, to the housefly, an incandescent-bulb-lit house slowly pulses from light to dark, so probably too with cheap line voltage choppers.
Indeed, to the housefly, an incandescent-bulb-lit house slowly pulses from light to dark, so probably too with cheap line voltage choppers.
This sounds amazing to me, but also confusing. My understanding is that an incandescent bulb works entirely by heating up the filament. There should be no way that the filament is cooling down and heating up in anywhere close to the rate that it would require to get some kind of wagon-wheel effect, which is what it sounds like you're describing.
The varying current through the tungsten will result in a varying power consumption (varying at a 60hz rate). The varying power consumption will result in a small amount of varying temperature on the filament.
Now, the filament does not cool down instantly, so the result is its temperature will vary by a few degrees, but likely not enough to ever be perceptible to human eyes. But with a sensitive enough (and fast reacting enough) temperature probe, one could likely measure the temperature rise/fall of the filament that is synchronized with the line frequency.
I'm not sure you've shown that this would be visible to a housefly as a "slow pulse from light to dark," as the post I was replying to claimed. First of all, you said the power consumption will vary at a 60hz rate, but it seems to me it will vary at a 120hz rate, since the current will be at its max magnitude twice per cycle (as you say in the first paragraph). But more to the point, I don't know whether the temperature/lumens will decrease enough in 1/120th of a second to be visible to houseflies or anything else.
Trying to research the answer, I found this physics lab worksheet [1] from Pasco (the makers of sensors), for a high school lab measuring the output frequency of incandescent bulbs vs fluorescent bulbs, but without doing the lab I don't know the results.
The numbers here show a >25% difference for an example bulb.
Also, even ignoring how the cooling starts off at its fastest, with radiation scaled to the fourth power of temperature... incandescent lights switch off in about a tenth of a second. Even if that was completely linear, it would be very visible. Even a 1% flicker would be visible.
https://www.youtube.com/watch?v=eUprJS9sXYU
https://www.youtube.com/watch?v=jXx5eEzMmYo
It's not an extreme brightness change, but it's possible to do a lot better.
Anecdotally from my experience as a macro photographer, the threshold for flies is lower than for dragonflies; flies often startle in response to movements almost too tiny to perceive having made, while dragonflies are relatively easy, usually requiring only a few minutes to approach from a distance of a meter or so to the ~12cm minimum focus distance of my best macro lens. (It's hard to know; the passage of time isn't of much interest in the focused flow state that's required for this sort of activity.) It helps that disturbed dragonflies tend much more often to return to the same perch, but with some practice it's possible to make the entire approach without disturbing them at all. The only really tricky part about it is that, when you're moving slowly enough, they also tend to land on you, which can be somewhat distracting if you're ticklish.
In any case, the existence of a minimum rate of change for perception of motion suggests that flickering light below a certain frequency might well be perceived as strongly discontinuous.
(It also merits mention that my macro rig includes three very powerful flash heads mounted around the lens front element. I've never observed dragonflies, wasps, bees, flies, or spiders to react to these in any way, even when firing from a distance of six inches; the only reaction I've seen has been from fall webworm caterpillars, which displayed a communal defensive response, and that may have been as much due to the shadow I cast, or to the polistid wasps hunting nearby, as to my flashes firing. The wasps notably did not care at all about me or my flashes, especially after they also found the nest and busied themselves with its rapid depopulation.)