HDR lightning vs. EV number (phisical camera setup)

[kontrolermpl]

Hello everyone!

I decided to write a couple words about my problem with HDR map lightning. So what`s the core? In the real world the photographer has no problem with the light environment settings, because it just exist! He has a photometer (light meter), and it just give him a correct EV value (f-number, & shutter speed) with respect to existing light power. My problem and question is, which value of light intensity must be to achieve correct value for HDR light (no mater if it is measure in lumens, default units or watts)? In my opinion most tutorials shows not correct way to achieve good results, because they setup first camera settings, and then change light of hdr value. Correct way is to change camera setup with respect to existing light power. Right? When we have of course natural light.




(we can see, that the wall next to shover has green color from grass - is that correct?)

Work-flow for this render is:

I made a simple environment lightning with OpenfootageNET_Plainfeld_medium.hdr in background and HEMI light as a texture. In the same time I opened the HDR image in HDRshop. I setup camera settings F-number: 5.6, Shutter speed: 60 - this is EV = 11. Maby for this map EV must by higher? I don`t know. So I change the intensity of HDR light from 1 to 60 (default values). The result from render looked like the same in image in HDRshop. Then I made interior scene and applied the same value to HDR map intensity (60) and now I just change the camera settings. This is complicated, but I want to keep the real settings.

From where can I get the correct value of HDR light intensity?

[Dariusz Makowski (Dadal)]

U might want to keep in mind that u need a true HDR image with full dynamic range of sun... - I havent come across one in commercial world yet... except for a lab test... Also u should use GI with brute force only model.

[andybot_cg]

I wish I understood a bit more the science behind real world light values, but alas, I don't. Basically, for me, if it looks correct with the default values, that's great. If not, I adjust it as I need it, keeping in mind real world camera exposures for interior shots. Your interior shot looks good, so keep going! For interiors with irradiance map, I would bump up the Hsph subdivision values to something like 70 or 90.

The green from the shower glass is probably from the fog value in the default glass. In my opinion the default is pretty strong - you can reduce this value and get less of that affect.

Andy

[kontrolermpl]

Thanks for reply. So I must try brute force method and check the result.

andybot_cg, you write:
"The green from the shower glass is probably from the fog value in the default glass. In my opinion the default is pretty strong - you can reduce this value and get less of that affect."

In my opinion the green on the wall is from GRASS (not glass) HDR map color. So I have a problem, and not just me, because grass from HDR image give a light. In real world grass and all around give just diffuse light from the sun and sky. In this situation grass take so much light as sky! So correct is make some big plane with mid-tone gray color around interior, right?

Can anybody share with us his HDR spherical lightning work-flow?

[kontrolermpl]

The previous image was done with plane with gray color around, and this image is done without it:



See the green bleeding at the white wall.

[andybot_cg]

doesn't sound like a good HDR! I've only used ones that are half-dome with only sky, no ground, just black below the horizon. I see what you mean about the color, I though the affect shadows through the glass was where you were directing attention. Have you tried testing any other HDR's for lighting?

[kontrolermpl]

Yes, I tried to used other HDR image from Openfootage website. For example: fielditalien_low.hdr. This map has more contrast. Thats mean using HDR shop for brows image and increasing EV value - sky is much more brighter than a grass, so green no bleeding at wall so much. More satisfied results give add middle tone gray plane around interior.

I repeat my request: Can anybody share with us his HDR spherical lightning work-flow?

[Dariusz Makowski (Dadal)]

My workflow... its quite simple. Go out to field snap 5x9 exposure usint my d800 and 8mm fisheye. Stitch it using ptgui or process to 16bit tiff to remove fring/process in pt gui. Load in HDR light studio in maya/other app and adjust the sun power and other parts of hdr to the moment when I'm happy with it...