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Thank you for these infos, and your time experimenting. It's extremely useful.
Unfortunately, there's still no extensive wiki about studio.
Guess what? I have it! I was thinking there was a product that found lights but I couldn't think of it's name. Just too many products in my runtime. Thanks for pointing it out, I've added it as custom action so I remember it.
That turned out really well. I feel like I'm sitting in a typical waiting room.
Good point, I haven't noticed that myself but see what you mean.
Good tip, I learn something new again.
Just letting you know I updated the title of this discussion by adding the words "for Low Light Scenes" to make it clear what these experiments were about.
That looks really good.
Sorry I went a bit OT with the hard edges thing but also I'm glad I did because of your excellent tip. As happens a lot these days, I know I have been given that tip before but I forget things all too often. I shall make a note of it (and then promptly forget that the note exists).
...OK since it cooled down here (finally) been performing some render tests and even at an exposure value of 4 it looks like a nuclear blast just went off. I have no environmental lights and am using only the Scene environment, no dome.
I have two coloured 40w bulbs in sconces on a wall three 75 w lights in teh ceiling (two of which are behind the camera) all shining downward, a light above a door with two 60 W bulbs, and a photometric spot light with a 20% spread at 300 lumens as a flashlight trained on a key card panel.
GPU is a Maxwell Titan-X.
ETA: removed the three ceiling lights and only a marginal improvement.
ETA 2: Found the culprits, two wall lights that were buried behind part of the framework not seen from the rendering camera POV that were set pretty high luminance and efficacy settings. . Reset them to 60w at default efficacy and much, much better. Now refining a few things like needing to get more light on the character to make her stand out better without affecting the surrounding area.
Currently running at EV 3 using ISO 64..
Did another experiment, this time an outside night scene.
Experiment 10: Ultrascenery Campfire
This is a night scene with no dome so the only light comes from the campfire. I set the campfire to 600 lumens and varied Exposure Value alone (other Iray settings at default).
Exposure Value = 1. Although this value was enough for an interior room, for this exterior scene the campfire reach is not far and so the scene is overly dark. Render time 1 min 56 sec.
Exposure Value = 0. Not sure what significance a zero value has but the slider has no lower limit. It does leave more light in and you can see more trunks.
Exposure Value = -1. Since there was no lower limit, I tried -1 and it works. Now needles in the woods to the right are becoming visible. Render time 2 min 54 sec.
Exposure Value = -3. You can see further into the background and there is a reasonable balance between light in the forest and deep shadows. Render time 6 min 32 sec.
Exposure Value = -5. Much of the adjacent woods are now lit. Render time 21 min 1 sec.
Exposure Value = -10. What the heck, let’s go for it. I jumped to -10 and got a very bright scene. Too much but look at how the needles shine. This led to much longer render times: 29 minutes 20 seconds
Conclusion: Don’t assume 1 or even 0 is as far down in Exposure Value you can go. It seems to be a continuous function and I’ve tested to a negative 10. Render times do get longer as the value decreases. I could have left Exposure Value alone and modified the intensity of the one light, but in a multi-light scene, changing EV is faster.
Brilliant! So useful.
Thank you.
Thank you! Thank you! Thank you!
I've added it to my toolbar, so I can access it with one click, since I use it often.
I've recently gotten into tonemapping and using real-world principles, and I've had a lot of success with it.
You do have to think like a camera. A movie camera, specifically. You need to light your night scenes the way Hollywood... err, would.
Here's a render with Aiko (using material settings stolen from a bluejaunte figure) inside Stonemason's Abandoned Interior. She's lit by a simple three-point lighting setup, all tinted blue with high temperatures to get a rich nighttime feel. I did my research and found real softboxes are typically 18x24 inches and emit 8,000 lumens, so I created rectangular spotlights lights to match that. I turned the key down to 6,000 and the fill down to 1,000 to make it moodier and more directional. The environment is lit by a single point light, set to Sphere 50cm and with 120,000 lumens.
For the exposure, I mimicked a real-world camera and set the render shutter speed to match the camera's focal length (70) and the render f-stop to match the camera's (32). Then I turned the ISO up until there was enough light, which in this case was 8,000.
And voila. Looks great.
This pic is literally the exact same scene, with the frame size lowered to 16 and the ISO turned up to 32,000. That's it. Like a real camera, you increase your ISO to increase the brightness, although unlike a real camera Iray doesn't seem to replicate the increased noise of a high ISO, so you can crank it up quite high.
Then I changed the ISO back to 8,000, since I wanted to be (somewhat) more physically accurate, and instead lowered the f-stop (on both the camera and the render settings) to 16. As you can see, the light level is exactly the same as 32,000 but the DOP is much higher due to the decreased f-stop. If I wanted to be super accurate while maintaining the same DOF, I would've just brightened the lights instead, but either way it turned out fine.
tl;dr
Ignore the Exposure Value. Set your shutter speed to match the camera's focal length and your f-stop to match the camera's f-stop, then increase the ISO (and/or your lumens) until it's bright enough.
...I spent many years with 3DL and loved the relative simplicity compared to Iray. For rendering I like the EV method because it keeps it simple and I can use "real world" light values (in watts or lumens) which I am used to from my theatrical lighting days.
I also did a fair amount of photography in the past.
In my photography days the fastest film I ever used was Ektar Professional 1000 ISO. My normal "go to" for outdoor daytime shooting was good old Kodachrome 64 and Ektachrome 64T. I also would push film ISO, but that tended to introduce increased graininess (and the entire roll had to be shot and processed at that speed)..
So I am used to camera settings, but Iray doesn't exactly behave the same way as physical film and real lenses. For example I've used the exposure setting tables for say Kodachrome 64 to set the tone mapping in Iray for an outdoor scene, but it doesn't quite give the same results as I'd get with actual film without fiddling around with various adjustments like white point, crush blacks, and saturation (something I never needed to worry about with a camera). If I waned a different "effect" there that's what filters are for (I used to do a lot of aerial photography so a skylight filter was always in the kit when I travelled). The only saving grace with 3D rendering is I'm not wasting expensive film on bad renders.
@margrave thanks for sharing your approach. There are many ways to accomplish something in Daz Studio and you show one (matching camera f/stop and focal length was new to me).
First, I agree that you need to add sufficient lights for a scene. I think of it more in terms of what I would do at my house rather than what Hollywood or Broadway would do as they use much brighter lights. If I want to light a room, I know having just one 60 watt light bulb won't be sufficient, unless I'm purposely modeling only having one light on.
Second, I did try setting the Shutter Speed to the focal length (which in my case is 65) and f/stop to match the camera (which is 22). I left ISO at the default of 100. Exposure Value automatically changes as you change shutter speed and f/stop, resulting in a value of 14.94. I knew this would be too dark but rendered it anyway. (I'm using the bedroom as it was setup for experiment 5).
I next upped ISO in stages. It was around 100,000 that I had something lit about as I did for Exposure Value=4.
I wanted something brighter yet and found I had to go to 400,000 ISO to match Exposure Value = 2.
My experiments were run with shutter speed and f/stop at default values. So I set them to 65 and 22 with ISO at 100. I then decreased Exposure Value to 4. This automatically changed Shutter speed to 0.033. I compare this to one of the renders at ISO of 200,00 and they are a close match.
At least in this scene, I can get similar results by simply reducing Exposure Value. I could change shutter speed, f/stop and ISO but that's extra steps for me and it's easier to type in a 4 instead of 200,000. I could add more light or change their intensity but I prefer setting them to real world values and vary EV. This is not to say that there aren't other reasons to change various tone mapping parameters.
I think Iray was just designed to mimic what Hollywood or Broadway would do, since that's given me the best results.
A higher f-stop will darken the image, so 22 is too high for a low-light scene. When Stanley Kubrick was filming Barry Lyndon, he had to order special lenses from NASA with an f-stop of 0.7 so he could film in candlelight.
This scene was rendered with a single point light set at 10 lumens. The tonemapper has a shutter speed of 70, an f-stop of 0.7, and an ISO of 6400. Generally, I set the shutter speed and f-stop first, based on the needs of my scene, and then I increase the ISO last in order to compensate. (Not that shutter speed matters, since Iray doesn't have motion blur, but I like to be accurate).
This is the scene with DOF Enabled. As you can see, there's quite a lot of it, which is probably why people don't film in candlelight too often.
The Exposure Value by itself doesn't seem to do anything besides change the shutter speed. That's why I think it's kind of useless; why use an abstracted value for the shutter speed when you could just set the shutter speed directly?
...upping ratings like luminosity or ISO to ludicrous levels is ridiculous and usually involves a lot of guesswork. This is why I prefer basing lighting on exposure value and using "real world" lighting values. Again in 3DL, lights have a value range of 0% to 100% which is just like theatrical lighting, very simple.
Prosumer cameras can have an ISO range up to 12800 or 25600, specifically meant for filming in low-light conditions.
I did some more tests, all using the same 10-lumen point light. The "reciprocal rule" I mentioned (the shutter speed should equal the focal length) is meant to reduce hand tremors in handheld camerawork. If I presume the camera is mounted on a tripod, filming a totally static scene, I can bump the shutter speed up to 1.0 (one second of exposure) while leaving the focal length at 70. That let me take this shot with an f-stop of 1.4, the typical lowest f-stop on a camera, and an ISO of 800.
For this one, I upped the f-stop to 2.8 and turned the ISO up to 3200 to get the same light level. Double the f-stop, quadruple the ISO.
Sure enough, putting the f-stop up to 5.6 and the ISO up to 12800 produces the same light level with less blur (assuming you match the camera f-stop and the render f-stop, as I did).
Finally, here's an f-stop of 8.0 with an ISO of 25600, which is the highest prosumer ISO setting I've seen used in my research.
Don't want to de-rail this interesting thread, but this is far from correct. If you use a standard spotlight with the default settings (no fall off) 100% might be sufficient. However, if you use a physically correct fall off you will need to use the intensity scale slider, often in the thousands, to make it useful. AoA lights are limited to 200% intensity, but I often find myself having to remove limits to get enough light. The OmUberarealight shader also needs intensities in the thousands range to work with physically correct fall off. Wowie's excellent PT Area light shader uses EV for intensity, although it has a light intensity slider for fine tuning. I could go on, but you get the picture;)
The reason to use Exposure Value is it's simplicity. In Daz Studio, EV and SS are related. Each time you halve SS, EV drops 1 unit. Halve again and another 1 EV drop. Increasing light sensitivity by reducing shutter speed requires using values between 128 (default) and 0.031 in ever smaller increments. So for myself, I can make even number changes in a small range and quickly get to a good lighting value (usually an EV around 1 or 2, sometimes -4 to 4), For those who know how to use camera settings and want to reapply that knowledge, they can use f/stop, shutter speed, and ISO. For others who are happy to point and shoot with their phone, they can use EV changes as an easier solution.
I agree with this.
EV is the easy way to adjust exposure with Tone Mapping in Daz Studio. On a real camera, different combinations of SS, ISO, and f/stop, which result in the same exposure, do make a difference in DOF (f/stop), motion blur (SS), grain (ISO). In Daz Studio, Tone Mapping settings don't affect any of that.
Also note that there is a strange behavior in Daz Studio Tone Mapping that calculates the displayed EV number differently when you adjust the ISO manually. I reported it to Daz as a bug years ago. Customer Service said it wasn't a bug.
So, you can adjust the overall exposure with either EV or SS, ISO, f/stop, but be wary about using both methods in combination. You may get unexpected results if you just go by the numbers.
Here is an example of the EV displaying a different value, for the same exposure:
This is the default tone mapping. It shows an EV of 13 for this exposure.
This is an adjusted tone mapping that results in the same exposure, but it displays an EV of 15.
Compare the viewport with the previous image. They look the same, because the equivalent exposure is the same. I doubled ISO and halved the exposure time by doubling the SS value. (1/256 is half of 1/128). EV is now displayed as 15, not 13, even though the scene exposure is identical. I find this confusing!
That's the other reason why I don't bother with Exposure Value. I have no idea how that value is calculated since, as you said, it gives completely different values if you change ISO or f-stop.
This explains EV.
https://en.wikipedia.org/wiki/Exposure_value
...hmm I never had that issue with 3DL lights, even when they added falloff to Point Lights. I did encounter having to pump up percentage values with UE in the few times I used it (which I thought was ludicrous) but rarely used UE because of it's appetite for system resources (particularly when I was still working on a 32 bit system).