What is the the irradiance (W/m^2) range of human vision?

Submitted by DeismAccountant t3_z4re36 in askscience

I’ve been putting something together that should graphically represent what an expanded human vision would look like, and while I have one axis (visible spectrum of 380nm to 700nm in wavelength) I’m not sure where the other axis falls, let alone how to directly convert lux to (W/m^2). The closest I can find is these two articles, with the second giving a minimum vision that seems equivalent to X-rays using the math I have. Even the conventional range of lux (100 microlux to 100 Kilolux) doesn’t feel like it’s expansive enough because it’s constrained to sunlight.

Edit: It specifically doesn’t feel sufficient because we can see stars in the night sky, as per the lux definition. the maximum is also too low because surfaces under the sun aren’t blinding.

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purpleoctopuppy t1_ixtgxg3 wrote

Going off this, nine photons in 100 ms at 510 nm is sufficient for people to see, which is 90 photons per second, or 3.5e-17 W. Pupil is about 8 mm across, so that's 5e-5 square metres, so on the order of e-12 W/square metre at the lower end.

Keep in mind our sensitivity to different wavelengths is different, so it's important that this is at 510 nm, and not generalisable beyond that.

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Bbrhuft t1_ixtmeue wrote

Replying to purpleoctopuppy (#680,150)

Researchers a few years ago discovered that humans can see single photons.

>Here we report that humans can detect a single-photon incident on the cornea with a probability significantly above chance. This was achieved by implementing a combination of a psychophysics procedure with a quantum light source that can generate single-photon states of light. We further discover that the probability of reporting a single photon is modulated by the presence of an earlier photon, suggesting a priming process that temporarily enhances the effective gain of the visual system on the timescale of seconds.

Tinsley, J.N., Molodtsov, M.I., Prevedel, R., Wartmann, D., Espigulé-Pons, J., Lauwers, M. and Vaziri, A., 2016. Direct detection of a single photon by humans. Nature communications, 7(1), pp.1-9.

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purpleoctopuppy t1_ixtmrws wrote

Replying to Bbrhuft (#680,798)

Oh cool! Last I read is that our eyes could detect a single photon, but our brain would filter it out, good to know there's been progress in this! Being a single-photon detector is a cool flex.

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Bbrhuft t1_ixvwxhc wrote

Replying to [deleted] (#690,307)

The energy carried by a single photon of 500 nm light is 4.0 × 10^−19 J.

The approximate conversion is 1 Lux = 0.0079 W/m^2 for sunlight that has a peak at 500 nm.

3.16 × 10^21 lux.

The brightness at noon at the equator is 111,000 lux, of which (albedo) for bright sand is 0.4. So sand in desert at the equator at noon, will be around 44,000 lux.

Which is a dynamic range of approximately 1.4 × 10^25 .

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