I downloaded DAZ Studio 4.8 late last night and did my first scene this morning. (My first try at 3D since using Poser 2 briefly many, many years ago)

I set up two spot lights as the only light sources hoping for a high-contrast render. In the Viewport pane it looked right; high contrast dramatic lighting, with one of the spots having a red color.

When I rendered (NVIDIA Iray) the lighting was very flat, bland and dark, and the red coloration of the main spot wasn't evident. Is the viewport pane more contrasty than the final render as a rule? Do I need to exaggerator any effects in viewpoet? Or am I just doing something wrong?

Any suggestions would be deeply appreciated.

Check the lights-you should have Photometetric lighting on if they are for Iray. If the package wasn't, that would be part of the issue. Also it would behoove you to use a HDRI environment map in the Render options in the Environment tab, along with checking to see in that tab if the selection for "scene and Dome" is selected so the render engine recognizes the other lights in your scene. Usually it defaults to Dome only for the Environment map that comes with the default option.

You're not doing anything wrong, in general the viewport is just an approximation of the actual render. As your renders use more and more sophisticated effects, the viewport becomes more and more approximate. That's how it's always been.

If you have the GPU power then you can set the main viewport to Iray rendering and get that accurate feedback you're after. For those of us with weaker GPUs... stick a small 'Auxiliary' viewport in a corner and it will show an Iray render at a size that your GPU can manage.

Check your Environment settings on the render tab. I believe by default the 'Environment Mode` maybe set to 'Dome and Scene' or 'Dome only' with a default low resolution HDRI on the dome. The 'Draw Dome' property is probably set to 'Off' so you don't see the dome in the render.

I suspect most of the light in your scene is coming from this default HDRI and your spot lights are probably not bright enough to add much light to the scene.

If you set the 'Environment Mode' to 'Scene Only' that will turn off the HDRI dome. Don't be surprised if your scene then renders very dark.

http://docs.daz3d.com/doku.php/public/software/dazstudio/4/referenceguide/interface/panes/render_settings/engine/nvidia_iray/environment/start

You can turn up the intensity of your lights, but make sure you do this in the photometric sections. A simpler way is to change the 'Tone Mapping' on the render tab. You can turn the ISO up until your get a render you like. You can use the "Nvida Iray" display style rather than the default 'Texture shaded' in the preview window to show you the actual lighting rather than doing a render. You can then change light intensities or Tone Mappings settings and see the results quickly, even it you do not have a Nvida graphics card. Just switch back to texture shaded once you get things setup.

http://docs.daz3d.com/doku.php/public/software/dazstudio/4/referenceguide/interface/panes/render_settings/engine/nvidia_iray/tone_mapping/start

Thank you everyone for your information. I have only been at this for a couple hours, so there's obviously a lot to learn. I wondered about the existence of a sky dome because I had patch of blue specular reflection on an object in the scene that looked for all the world like reflected sky. I "fixed" by messing with the object's surface properties. Now I know what to look for.

Thanks. again.