In 4.8 I used a distant light to get a decent light for rendering. I don't like the way Environment lighting looks - it washes out the image.

In 4.9 the distant light won't light the scene. Even at intensity 200%, if the Environment Intensity is 0, the render is dark.

What has changed? I don't like it!

The Intensity dial doesn't really work on Iray photometric lights and if you don't have 'Show Hidden' checked for the parameter option you won't even see it

Oops! Just checked and the Intensity dial is still visible with 'Show Hidden' checked in the latest Studio, however it doesn't seem to much impact on the light. It may change the fall off distant at rendering which would show in large scene. To truly increase the amount of light adjust the lumens.

You should use "Luminous flux" instead of intensity.

Lighting an Iray scene is a combination of the scene lighting and render settings which act like a real world camera & lighting setup. If you find the scene is to dark it will either be the amount of light or the the Render settings you need to adjust to bring it up further.

Adjusting the luminous flux is the obvious way of boosting the light in the scene, but it's easy to overdo and putting a large bright light on your scene may effect the realness of your render. You can also change the light measurement system for Luminous flux from Lumens to watts with which we all seem to be a bit more familiar with due to home light bulb measurements.

Another thing to adjust is in the Render settings and is the Tone Mapping panel, here you will find many normal photographic type controls Iray needs adjustment the same way a DSLR camera does. Settings that work great in a cosy fireside nook of an old house are just not going to work on bright sunny day at the beach the same as a real camera.

The main option to look at is the Exposure setting: "Each increment or decrement in this value corresponds to halving or doubling, respectively, the effective exposure as expressed in the resultant change in the Shutter Speed value. Higher values yield darker images, and lower values yield brighter images."

Adjusting this setting is basically adjusting your virtual camera to be more or less sensitive to the light, just as you would with a real camera.

Thank you for the replies. After some more tinkering, I see the iray lighting in 4.9 is better - not sure what changed. The types of adjustments folks mentioned do wonders.

There were no changes to lighting between 4.8 and 4.9.

Distant Lights should be, mostly, relegated to the trash bin of history.

An example of what you are trying to accomplish would help others to help you.

OK, I will provide some examples.