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Tone mapping problems

MendomanMendoman Posts: 404
in The Commons

It's been a while since I last rendered indoors images, and probably something has been changed since then, but I think I used to change tone mapping values like Exposure, Film ISO etc. to brighten my indoor environments. My current light setup is sun-sky and some ghost lights in the room with windows. I'd rather not increase ghost lights luminance, since they tend to wash details away, so I tried it with tone mapping. I made some tests, and it looks really good, but as soon as I brighten the room by lowering exposure or increasing Film ISO, my render time increased a lot immediately. Anybody else is experiencing this, and is there a way around this like tone mapping combination that does not increase render times? Of course I can take my images to Gimp and increase brightness, but I was hoping there was some trick to do it in DS.

Comments

  • L'AdairL'Adair Posts: 9,479
    edited October 2019

    @Mendoman, Try it the other way around. Use the lights to make the image too bright, and then use Tone Mapping to darken the image.

    Iray renders faster with more light. I don't know why it would take longer to render the same image with the same lighting by using Tone Mapping to make the image lighter, though.

    Post edited by L'Adair on
  • fred9803fred9803 Posts: 1,565
    L'Adair said:

    ...... I don't know why it would take longer to render the same image with the same lighting by using Tone Mapping to make the image lighter, though.

    The more light that gets to the canvas the less passes it will take to reach 100% convergence and the higher your convergence is at the end of a render, the less noise will reamain in your image.

    The amount of light will not change the time that your GPU takes per itteration, but it will generate higher quality itterations in the same time.

  • MendomanMendoman Posts: 404

    @L'Adair Good idea, but I couldn't quite pull it off. I had to increase the light intensity of my sun-sky so it wouldn't look so dark, but then shadows outside went bonkers. As a positive note, with little tweaking I still managed to lower render times by increasing light source values and making the image darker in tone mapping, but only to a degree. Too much, and then it went much slower again. It was still a bit of a surprise that those tone mapping values actually effect render times, since I thought they are more like a image manipulation post effects. Oh well, you live and you learn, so I suppose it's easier to just use gimp to brighten the images in post. Thanks for the help though.

  • JonnyRayJonnyRay Posts: 1,744

    Basically, anything you ask the rendering engine to do is going to have a performance impact. To get the absolute fastest rendering, turn Tone Mapping off completely. But you'll want to use Iray Canvases and be ready to adjust exposure post-rendering if you do that because your render is going to look pure white.

    While I completely agree with L'Adair that starting with more light and toning it down is generally better, there can be issues there too. One of the reasons people complain about how much light they have to add to interior scenes is because the default Exposure tone mapping setting is designed for an outdoor scene. Just as photographers have to adjust when they move to shoot indoors (or these days their cameras probably adjust for them), we need to tell Studio that it should brighten our indoor images.

    On a related note, when adjusting the exposure in the Iray Render Settings, I normally recommend people only worry about the Exposure slider. Since you don't have to worry about tradeoffs like depth of field and motion blur like you would in a real camera, the Film ISO, f-stop, etc. settings can be more hassle than they're work. Just slide the Exposure setting until it looks about right and let Studio do whatever weird stuff it wants to your shutter speed. :)

  • SevrinSevrin Posts: 6,313
    JonnyRay said:

    Basically, anything you ask the rendering engine to do is going to have a performance impact. To get the absolute fastest rendering, turn Tone Mapping off completely. But you'll want to use Iray Canvases and be ready to adjust exposure post-rendering if you do that because your render is going to look pure white.

     

    Another benefit of using canvasses is that, since you're going to adjust exposure and lighting in post anyway, you might as well turn up the lights to speed up your render.  Exposing for the shadows and developing for the highlights, and all.  Even if all you ever use is a single beauty canvas, having a high dynamic range image to work with gives you a lot of options in post work.

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