Timeline for Why is there no strong contrast between inside and outside the tunnel in my Blender animation?
Current License: CC BY-SA 4.0
15 events
| when toggle format | what | by | license | comment | |
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| 16 hours ago | comment | added | Gordon Brinkmann | @MartynasŽiemys As I said to Markus, the values in my answer were never meant to be absolutely correct and expecially not about giving the various range of conditions daylight might have, just to give an idea how far away the default values might be from "real" values. As I said, I already went into too much detail in my answer, because basically the OP 1. was just wondering why there is no kind of auto-exposure happening in the Blender camera and 2. was surprised to learn that an HDRI with default Strength 1 is not real world lighting power. | |
| 16 hours ago | comment | added | Gordon Brinkmann | @MartynasŽiemys Good point, although one of the sites where I found a power value of around 1000 W/m² was explicitly mentioning that the power varies over the different wavelengths, but of course the light does not hit the surface split up but all at once etc., I'm not having the details in my head but to sum it up this 1000 W/m² was meant to be the visible light range. Anyway, I think the whole discussion you unfortunately missed was going much too much into physical detail, even my answer was too detailed for the original question :D | |
| yesterday | comment | added | Martynas Žiemys | I see you had a party here discussing Sun brightness. I regret I missed that. :D I think it's better to consider ground illumination. Easy to measure with 30 euro device. Also easier to find info Radiance is also very confusing in Blender. Blender lights consider radiance of only visible spectrum, which is not really what physicists talk about when saying radiance of the Sun, is it?.. Very confusing. | |
| yesterday | comment | added | Lutzi | @GordonBrinkmann I was just highlighting that Filmic shouldn't be used (according to the manual), just a precision for the OP. For the rest I haven't said anything about it so nothing to say there. | |
| yesterday | comment | added | Gordon Brinkmann | @Lutzi Or in mathematical terms: CM exposure of $x$ means a factor of $2^x$ times the scene's brightness whatever this is, while a Film exposure of $x$ means a factor of $x$ times the scene's brightness. And after rendering, the Film exposure setting cannot be altered, while the CM exposure can. | |
| yesterday | comment | added | Gordon Brinkmann | @Lutzi I know, I use Filmic because in some cases I like it more. I never said this is what the OP should use or anything, the answer was solely focusing on what the different exposure settings in Film (the submenu where you can also set the background transparent, not Filmic in CM) and Color Management mean for the image brightness and what their units are. No matter if Filmic or AgX, the Exposure of 0 there means 100% of brightness according to the scene lighting, -1 means 50%. And the Film exposure at 1 means 100% and 0.5 is 50%. This is not obvious to all. | |
| yesterday | comment | added | Gordon Brinkmann | @MarkusvonBroady The 1000 W/m² should be the reference, true - guess why that is the value I used in my example? 😉 And that's why I used 160 for the world strength because it's just a little less than 1/6 of 1000. But as I said, my answer was never about giving perfect physically correct values, just to show the large discrepancies between HDRIs at 1 and real world brightness. But this discussion can probably shine a little more light onto this topic ( see what I did there? 😁) for the OP as well. | |
| yesterday | comment | added | Markus von Broady | The 1360 is what you would experience on the International Space Station. The 1000 is the clear sky on the sea-level. So for a usual render, being on the ground, 1000 W/m² should be the reference, and also this value should be compared to the sky irradiation, because when you're on the top of the atmosphere you don't even see the sky, and shadows are much closer to black. | |
| yesterday | comment | added | Lutzi | @GordonBrinkmann Note that Filmic is deprecated and superseded by AgX docs.blender.org/manual/en/latest/render/…. | |
| yesterday | comment | added | Gordon Brinkmann | @MarkusvonBroady For the sky values it is the same as the sun, I tried to give an average value. For clear sky I found values like 160 to 200 W/m² on some pages or the factor 1/6 on some, and other sites stated 20,000 lumen with a sun having 120,000 lumen which is also a ratio of 1/6. After all, my goal here was not to give a reference table for all kinds of scenarios, weather, time of day, season etc. I was just trying to give an idea why the values in the question do not seem to be very realistic and what differences there are between Blender and real cameras regarding exposure. | |
| yesterday | comment | added | Gordon Brinkmann | @MarkusvonBroady Actually I found different sources with different values and tried to average them out. And although varying, they had often roughly the same values. The 1360 W/m² (it was 1361 on one site if I remember correctly) was given as average value for the average Earth-Sun distance at clear skies. Of course the brightness of the sun varies with season, daytime, weather conditions etc., and so does the brightness of the sky as well - but for that matter, I mentioned "clear sky" several times. | |
| yesterday | comment | added | Gordon Brinkmann | @MarkusvonBroady How darkness is related to JPG format? I'm not talking about general possible values in all kinds of images, I'm talking about downloaded HDRIs to use as environment lighting, as it seems the OP is asking about them. So it is related to JPG in such a way that usually HDRIs specifically created to light environments have brightness values that exceed the 0 to 1 range, which JPGs have not - so loading a JPG into an Environment Texture node will almost always result in a darker scene than using a dedicated HDRI when set to the same Strength value. | |
| yesterday | comment | added | Markus von Broady | So I think multiplying the higher value of the two by a ratio of sky-to-Sun strength doesn't make sense. BTW I find wildly different claims as for this sky/Sun relation, so it would be nice to know the source. Intuitively the difference is much greater but this is because eye response (brightness) isn't linearly correlated with real strength (irradiation). I think it's somewhere between ⅕ to ⅙ in perfect conditions down to as low as about 1⁄₂₀ | |
| yesterday | comment | added | Markus von Broady | "But the scene looks so dark as if it was just a JPG." - I don't follow, how is darkness related to JPG file format? "the sun at a power of about 1000 to 1360 W/m²" - I think it would be nice to link to Wikipedia here, as there's a lot of nuance to this: in particular, the higher end of the range is the irradiance at the top of atmosphere, and the lower end at ground level with perfect conditions (clear sky). The missing ~360 W/m² is what is attenuated and bounced both to cosmos and to ground as sky color. | |
| yesterday | history | answered | Gordon Brinkmann | CC BY-SA 4.0 |