4.19 Physical Lights

[rosegoldslugs]

@A-J-K

That means a value of 1Lux for the directional light “moon” is correct? The problem i have with the current physical lighting setup in Ue4 is, 1Lux gives me no lighting at all in my scene.
I also have a problem with this data charts, i don’t really know how to match the terms in the charts with the editor ones, f number is a clear thing, it’s the f-stop in the editor… values like 1/125, 1/100 or 1/30 are the shutter speed values… but where are the ISO numbers ? I guess they are always the same like the shutter speed? And what is EV ? Exposure Values… Is it the Min and Max Brigthness in the Exposure tab ? or the Exposure Compensation value ?

The chart gives me also shutter speed values like 1 or 2 or 60, without the 1/ , the same goes for 2m, 4m, 8m, up to 256m and so on… how should i use this values ?

And for the simple sunny 16 rule setup like from Daedalus51’s video, Lumen and Candela values are still absolutely not working for me.

1 Lux will only be visible if your exposure is correct. Night time can get into the negative EVs, so 1 Lux will absolutely be visible then. EV is a simplified way of talking about exposure. Just gonna quote myself here cause I’m lazy

@rosegoldslugs

It’s a single unit based on shutter speed, ISO(generally 100), and f/stop to where any combination that has equal exposure to another combination would use the same EV. Instead of worrying about the individual settings, you can use the EV input. Plus, it provides a real-world measured reference that can get you 90% of the way there just like other physical units. For instance, interiors will likely be around 4 - 8 because of the average luminance found in interiors, but with Auto-Exposure now directly using EVs, we can also adjust for the exposure outside if you get near a window, like up to 13 for the overcast day outside in my scene…

…An EV of 5 is identical to a shutter speed of 1/4s with an f-stop of 2.8 at ISO 100. It’s also identical to a shutter speed of 1s, ISO 100, and a f-stop of 5.6 because both combinations of settings will result in identical exposure. EV5 is just a simpler way to put it.

They’re used in the engine by default as the viewport exposure override, unless you enable the extended range option in the Project Settings, which will replace the Min/Max Exposure values for EVs in the Post-Process Volume. Regardless, the Manual mode can achieve identical results, you just have to convert the single EV value to the individual camera settings.

To use the chart for matching EV to manual settings, just set your Post-Process Volume’s Metering Mode to Manual and set the correct values down in the Camera section. Most measurements will be based on ISO 100, that chart included. So because of that, and because the Shutter Speed input is limited to 1/1(1 second), some of the chart is irrelevant. You could do some math to get the required Shutter Speed and F-Stop for a different ISO, but since the manual settings don’t really change anything else it doesn’t matter imo.

Considering that the Sunny 15/16 rule is targeted towards exposing for a subject in direct sun on a clear day, I wouldn’t expect your every day light to be visible then. It’s the same concept of your car’s headlights not visible during the day, excluding the actual light emitting surface since that is always waaaaay brighter. Or your phone screen not being visible out in the sun or it blinding at night.