Different brightness calibration between C4D and Max? (Solved)

[Rhodesy]

Hi Im a long time C4D/Corona user but starting to bite the bullet and learn max. Just installed the corona demo and trying out some materials. I to get the right brightness calibration for a scene I have put a plane in and a simple cube, a corona sun and sky and a camera with -3EV and 3 highlight comp. I have put on a white material to both the objects with level 1 and RGB value 180. Also a reflection gloss of 0.4. I have set up the same scene in C4D with a white value of 70% whit equates to RGB 179, so close enough.

Anyway when rendering and right clicking on the face of the cube in direct sun in C4D I get values between 230 and 240 RGB which looks about right to me but in max they are burnt hard up against 255. Both these scenes are set up as close as I can but its hard to get a specific sun angle in MAX (is there a degree gizmo for rotation and height in the max version?)

Anyway, any clues on this and which is correct would be helpful as I want to get an accurate start on these materials and both to look the same in C4D and Max.

Thanks

[PROH]

Hi. Don't know is this will help, but personally I would avoid the highlight comp. and set it to 1 and EV to something around -4,5 (for Corona Sun & Sky), or EV -5,6 + Kim Armland Photographic LUT.

[Rhodesy]

Interesting tip thanks. How do you control the highlights then or do you always under expose a bit? Do you save out as 32bit and have a 32 bit workflow in PS? I find 32bit files absolutely huge if I've got 8-10 element passes and an 8K+ image size.

[PROH]

Hmmm... maybe some would think I underexpose, but I don't think so. I do use highlight comp if absolutely needed, but I don't set up my lighting and materials with it on.

Regarding PS workflow: I does as much of the job as possible in the renderer, and seldom uses 32bit to PS.

[romullus]

Both these scenes are set up as close as I can but its hard to get a specific sun angle in MAX (is there a degree gizmo for rotation and height in the max version?)

Yes, there is. Uncheck "targeted" in the sun object and go to select and rotate mode. Now with transform type in (located under timeline, or can be summoned with F12), you can control sun position precisely. X controls zenith angle and Z controls azimuth angle.

As for brightness mismatch, i would try to check if there's something wrong with gamma settings in either C4D or 3ds max. The easiest way to check this, would be as follows: reset all tonemapping controls to its default settings, turn off sun and sky (and any additional light) and set pure white colour as enviroment lighting, also turn off reflection for your material. Now render your scene and sample colour from your object, if it matches exactly to what you have entered at material level, then everything is fine with gamma and the problem is somwhere else.

[Rhodesy]

Thanks for the tip on the sun Romullus. Seems to work fine.

Re the brightness or gamma issue. I will have a go at setting up those identical scenes again but actually the material balls tell a story. Please see the attached material screen grabs from c4d and max. both of these are just diffuse 100 RGB. The c4d one is significantly darker than the max one of the same value and to be honest I would say the c4d one is correct for 100/255 (or really 100/200 useable range). The max one is still very bright to my eyes for such a low value.

System setup is c4d natively has LWF on by default and something I've never changed. Max is also default and looks to be 2.2 gamma but im still new to max. using Corona 2 demo.
Does that max preview ball at 100RGB look odd to anyone else?

Thanks

[Rhodesy]

So in C4D the default option is LWF on and input colour profile as sRGB. You can change this input colour to linear and all the shader balls lighten up so the RGB100 diffuse ball looks the same as max.

We've never been told to change any of the default C4D options for corona as far as I know so if the two systems are working on different principles its something that should be flagged. Also in photoshop 100RGB looks the same as we get in C4D so I would guess C4D is more correct but I could be wrong? From what I understood was Corona does all the thinking under the hud - we just put our regular sRGB textures and colours in the slots. Unfortunately I need to crack on with another task just now but I'll be revisiting this later.

[romullus]

My 3ds max shader ball at 100 RGB is as bright as yours and i think it is correct. From your description, it looks that C4D default settings are correct too. Don't know why it renders darker though.

P.S. shader ball isn't absolute reference - in 3ds max  it is possible to set material previews darker to pre-linear workflow look, yet still get correct rendering.

EDIT: could you show two rendered examples from 3ds max and C4D to see how they are different?

[sprayer]

My shader ball the same as your in c4d =)
http://imagizer.imageshack.com/img921/9933/7bF7N7.jpg
Did you set gamma 2.2 in settings 3ds max and c4d?

But after choosing 100 color is save as 101 o_O i though this issue only for 0-13 range

[romullus]

Actually, your shader ball displaying material with sRGB 100 and Rhodesy explicitly mentioned RGB 100. If you'd set colour to 100 RGB, your shader ball would be much brighter.

[sprayer]

Ok, maybe Rhodesy have the same convertion in c4d?
http://c4d.cn/help/US/pics/030151.jpg

[Rhodesy]

Thanks so much Sprayer and Romulus. The issue was simply related to just using the native max colour picker instead of the corona one which allows srgb values like we get in c4d. C4d natively has srgb input activated but with max it's linear by default so the two values look different. I didn't realise corona for max had to come up with their own colour picker for this to work and it's not on by default which is confusing.

So now I can have 70% white again for my white walls and they will look the same in both max and c4d. I'm guessing everyone uses the corona picker? Hence the recommended 180 rgb value (or 70%) is actually srgb? and should look like it's in the same range as any correct textures? Previously in testing, just using the Max picker at 180rgb the white was too bright for the surrounding textures so I had to clamp too much and the DR was reduced more than I would like.

Question is should I be using standard 180 rgb and brightening up all my textures and using more clamp (4/5 rather than 2/3 range for sunny outdoors)? I'm hoping not but I'm here to learn! Thanks

[romullus]

Actually if we're talking about whites, then i think that 180 is RGB. My whites usually are in 210-230 sRGB range.

[Rhodesy]

This is interesting and I've started a thread in the c4d forum so maybe there might be some input from the devs there. I just think there should be some clarification. There are only a few rules in corona so it's important both platforms have the same guides.