Hello,
When working to an interior scene lighted from the windows by a (natural) HDRI (Dome or Env), the extra (artificial) light added to the scene have to be boost incredibly (like a 50w IES by 5000% or even more).
The relation between the HDRI (natural)/vray light (artificial)are not matching the reality at all. A 50W bulb 20 cm away from a wall, such wall under shadow, with a large open windows, even on a shinny day, will be visible on the wall, but not in vray.
On such scene, you start to play with incredible numbers and more light you have (IES, Vray IES, Plane, vraylightmatl…) and more difficult it is to have the lighting balance properly because we lost the roots of physical rules.
I didn’t try yest but I guess a vray sun may raise the same problem.
Maybe a solution will be to lower the HDRI intensity around 0.01!
whatever looks right… since you are not trying to do a simulation.
you can start backward…put all the lights like is a night shot(at 100%), use your camera exposure to get the light that you want and turn on the dome invisible… use a copy of your hdri for the background so you can control it independently
thanks, we share the same approach. But then to get enough light out of the dome, you can’t get it too low and them again you have to crank up all artificial light by a big amount.
But again, the main idea of using a physical cam, is to stick as much as possible to the physic, so at least there (from my point of view) the work is done with real ref from the real world.
usually I like to have diffuse light coming from the windows if I have artificial lights on. HDRIs are not physical accurate in my opinion, it’s a representation of an specific hour of the day with multiple exposures but you still need to move gamma or intensity to looks like you want. the backplates that come with the HDRI help to calibrate them as well as the cameras. if you see professional pictures and you have a lot natural light coming in you rarely see the artificial lights (the cone) … specially if it’s white light.
That depends and the end goal, I’ve had a number of jobs over the years where the client inisted in seeing what a shop will look like with a specific light fitting, from that they would know to add more lights or not…
If you ever have to choose between using crazy unrealistic values for either your VrayLights or your HDRI, choose the HDRI. I would always keep my VrayLights to proper values. Makes managing things far simpler and the way the lights work with materials and the camera will be far more reliable and consistent.
Doesn’t make a bit of difference. If the light is twice as bright as the rest of the things in the scene it doesnt matter what numbers are in play to make it so.
But if you’re trying to work with real kelvin temps and light power etc. then it’s going to be a nightmare if they’re all out of whack. It’s far simpler to keep them all within real-world values then tweak your overall lighting and/or HDRI etc. to get the general levels correct. It also means that when you bring in other lights and models from your library which also have real-world values, they will work perfectly in the scene. In a typical interior scene with perhaps 10 different real lights and one HDRI, it’s a lot quicker and simpler to play around with the HDRI and your camera/exposure than starting to fiddle with those 10 lights.
How will it be a nightmare if they’re out of whack? If it’s too bright, drop the number, if it’s too orange, raise the temp etc. everything else is irrelevant, it’s just about as simple as it could possibly be.
Because if you keep things in real-world values, or at least close, initially, then it’s much easier to spot when something’s looking wrong down the line. If all your lights are between 800 and 100000 watts and kelvin temps equivalent to 200 or 9000 then it’s going to be harder to spot when there’s an issue and much harder to balance things. Same with the temperatures. It’s much easier to diagnose exposure and white balance issues if you keep things simple and realistic as a base. You can then obviously start moving things around to make it look good, but if you start from a base of unrealistic values it’s more likely that you’ll run into trouble later. This sort of workflow avoids those issues. Just my opinion on my own workflow.
I still think it’s easier to just look at the image and use my eyes to see if anything looks wrong. it’s pretty easy to see if something is twice or half as bright as it should be.
i am definitely in the “if it looks good” camp, but i wholeheartedly agree about starting from a realistic base being a timesaver.
if youve got everything cranked to unrealistic values, then try to do another view of the scene, suddenly you find it doesnt work..
example: interior with lights adjusted to look right, try camera outside, windows are unrealistically bright for a daylit scene. pain in the arse cos you need 2 light setups.
this is exactly the issue im dealing with now.
having said that, i suspect that using sun and sky, and physical values for lights, plus physical camera, will be the right balance - dont think for a second chaos would allow their physical system to be so out of whack.. its more likely the materials and exposure/burn are not physically correct or something.
Yep this is basically my approach. Ultimately it’s all about whatever looks right, of course, but the way you get there is important because it can save a huge amount of head scratching and issues down the line when working with other assets, other people, other studios or just trying to diagnose issues with your scene. I just don’t see any sense in beginning your scene with crazy values when you’re trying to avoid issues. You will always minimise the chances of issues arising if you try to keep everything within real-world values. You can then start playing around with things once you have a good balance. A good example is neon light - it just never looks right with real world values. But if your surrounding scene is also chock full of crazy values then it’s going to be super tricky to get the neon to work properly.
My job is to do renders before construction for client approval in very short deadlines. Museums, expos, pavilions, planetariums etc Most of the times I just try to make it look good, but there are hundreds of times that we need to find an approximate lighting scheme that works to feed in the the work of the real life light designers. When they suggest to us a specific light fitting I would love to test it easily in Lumens or something like that. I usually work with a vray sun, hdri, vray lights plus loads of lightboxes, LED strips video projections, frosted glass etc. Things can go out of hand really early on, I would love to have an easy way to unify all these. For our practice we don’t need 100% photoreal behaviour but an easy way to test real life lights would be really helpful. I am not even sure what a realistic value for the sun and the HDRI are. I usually have the sun at 1 the HDRI multiplied by 100 ? and then my lights start from 60 to 120. The same goes if i use sun 1 and vray sky 1. Which is obviously not right because a 60 multiplier is 37000 lumens almost a football stadium light.
I have been of the camp ‘make it look right’ but some times i need more than that.
i think the default values for sun and sky are based on physically correct values. hence the “physical” tag. in theory if you use those, the physical camera, ies lights with correct values, set vray to not do any fancy colour correction, and get your *materials* physically correct, the result shoulnt be wide of the “physically correct” mark.
OK, I’m happy to see that I’m not facing alone this nightmare. Seems that there is no physical accurate process at the moment.
This thread was not about physical accurate lighting vs non accurate tweak lighting. It was about trying to find out if there is a way to match as much as possible the real word to gain time. I know what means 60w spot, I have now idea what means 6000w or 60000w, or even worst lumens (thanks to Alexnode, now we know what mean 37000 lumens).
It will be great to get somebody from Chaos to give a feedback on this subject.
The balance between internal and external lighting has always been something i’ve tried to find a solution/workflow for. I definitely try and go down the physically accurate route setting up the internal lights to realistic (or close to realistic) values. But before i worry about that i setup my camera to settings i would expect to use as a starting point in a real world scenario. Those of you that have heard of the sunny16 rule will know that there are fairly specific guides to a range of lighting scenarios. (See attached a chart that i knocked up for the studio).
These are obviously guides, not law, but they’re a good starting point! I start off with these settings, so for an internal something like F2.8, shutter speed 1/125 and ISO 100. Since the level of light you get from your HDRI can differ entirely depending on who has shot it and what number of stops have been used to capture it, therefore there is never a truly accurate value to set it at as per the values of the vray lights. Therefore i boost the render output value of the HDRI (leaving the vray dome light on 1.0) until i a level of light in the scene i’m happy with. I’ll then turn on my internal lights individually or in groups depending on how i want to go about lighting the room. 9 times out of 10 they’ll only need minor tweaks if any.
Thank you Matt this table looks great i already put it on the wall !
In the previous century : ) is used to buy 400 iso to 1600 iso film for interiors depending on the lighting conditions … There was no way that you could capture a dark interior in a 200 iso film. Never used flash in my entire life!
I have to say that I still find all these settings a bit of an anachronism in DSLRs and in Vray. You don’t have silver crystals in film because there is no film.
You shoot ‘gigapixels’ you touch your point you focus and from time to time you adjust the exposure if the setting is unusual or you want to darken it or to burn the shot. Rule of thumb for me is to do that in post-processing and capture as much information as possible.
From my point of view there is only exposure and geography. The ideal workflow for my type of work would have been to have an exposure 1 is something like midday, summer 30th parallel north and south. So you set up time - day - place - atmosphere you define north in your drawing. Automatically you have a suggested exposure. Mental ray tried that and it wasn’t that bad. The feature that would make my life much easier though would have been to have light materials, multi- sub object self illuminated materials and vray lights to behave the same way. All being displayed in the light lister with three quality presets. When i usually break my scene is with self illuminating materials. Small peculiar led strips, led walls with frosted effect, video projections, colour printed lightboxes . Things change so quickly as we design that spending time turning multi-subobject material meshes to lights becomes a no go. So i usually fiddle with it until it looks right and after a while I start using all sort of values that have nothing to do with reality. In the middle of this mess a light designer comes in and starts throwing light fittings in lumens …
