Setting power multiplier- Newbie questions

[likesdalmations]

My 10'x15' kitchen is lit by 8 par30 lamps ceiling downlights (about 800 lumens each). The adjacent 7'x7' breakfast area is lit by 1 semi flush ceiling fixture with a diffuser also about 800 lumens output. The resulting render shows an unexpectedly large difference is the surface illumination created by these lights. I do realize there is a large difference in lumens being generated in the kitchen but the breakfast area looks abnormally dark. I am using ies files for all sources and a power multiplier of 1 for all. I also placed several virtual gray scales in the rooms for uniform comparison. They verified my observations that the kitchen is very much brighter than the breakfast area. Sunlight is off since there are many windows. This is a very useful app and thanks in advance for your advice!

Questions:
1) What is the intended purpose of the power multiplier and why would I use it or not use it?
2) Is it best to leave power multiplier at 1 always and use post tools to improve the appearance of the render?
3) If I am using ies sources and light sources without ies files in the same scene can I expect the illumination to be comparable?
4) Is there an incident light meter tool in Twilight Render or another app that would measure illumination levels?

[Chris]

Your image is not attached by I can address your questions.

1 & 2, Generally if you are trying for a realistic appearance, you should leave the multiplier at 1 so that it correctly represents the lumen intensity of the original IES.
3, Yes the light intensity is all on the same scale (lumens)
4. TWR does not have such a tool.

If I understand your description correctly, your kitchen is 8x more brightly lit than your dining area. So.... that would be a considerable difference!

[likesdalmations]

Original verbose reply disappeared!

Kitchen-0-6C REV 2.2_Scene 1.jpg (699.68 KiB) Viewed 3691 times

Bottom line: I did find an error in my ies file settings for the kitchen. The attached image seems more true to life after the fix. Kitchen is dimmed to 80% in the image. Note the gray scales (made from Sketchup paints) I wish I new more about how to quantitatively how to interpret the results. Qualitatively I feel that if I can see all the steps and they are distinct from adjacent steps then I am in the right ballpark. Thanks again for your help.

[Fletch]

If I understand correctly, I agree with Chris, you have 8x800lumens in RoomA, and 1x800lumens in RoomB, so, naturally, 8x brighter in RoomA. Unless you have outside light entering RoomB?

Do you think 800 Lumens is very low for a dining room? (1300 Lumens is a single 100w incandescent light bulb.)

You could do a little test like attached, placing different lights in the 2 spaces and rendering to see results. Try with Spots, setting power in Lumens and remember to try setting proper Kelvin Color, then try with IES, open both test renders to see if the lumen output of the IES test and the lumen output of the Twilight Spot-set-by-lumen output compare in a photo editing program.

It is CRUCIAL to use the right exposure setting in the Twilight Render Dialog under "Post-process". Play with the settings when your render is done and see what a difference it makes in your scene.