Gamma Issues again i think

[Dave Buckley]

Just converted to vray and when i create scenes from scratch, i have max preferences gamma set at 2.2 along with the input gamma set at 2.2 (i change the input gamma to 1 when using hdr) i also set my gamma in my colour mapping gamma setting to 2.2 regardless of which colour mapping method i use. with this all is well and good renders look nice vibrant and how they should do.

 

however when i open some of the evermotion interiors, i delete all lights and environments and apply the method i mention above with my own lights and cameras that i would expect to work as it has been like mentioned above.

 

but it doesn't, the scenes become really washed out.

 

i have done a bit of reading and i think it might be something to do with the textures when the evermotion scenes were created. do i need to colour correct (gamma correct) the textures in the scene or am i way off???

 

i just don't understand why my method works when creating scenes from scratch and why it doesn't work when i open scenes that have been create by others.

 

the same also happened with a scene i downloaded from the web. i had been following the hdri tutorials on aversis website. when i creat a scene from scratch like they do and follow the instructions it looks great, however i open a scene i downloaded, and go back through the instructions on the aversis website to apply the same technique using the same hdr etc, and hey presto it looks washed out again. if i then change the gamma in the colour mapping settings back to 1 then the scenes look how they should. which tells me it is something to do with textures maybe???

 

i'm slightly confused. please shed some light

[Dave Buckley]

ok so for the following tests my max preferences gamma is set to 2.2, the input is set to 2.2 and the output is set to 1.0 as i have changed the output in my tests.

 

on the top of each window where it says gamma ??? this is referring to the value that i have set in the vray colour mapping rollout, colour mapping on each 1 is set to linear.

 

hdr in environment and reflect with default values. ir +lc for gi adaptive dmc and catmull rom, basically all settings are same for each render - the gamma settings

 

it seems to me that i can leave the colour mapping gamma setting at 1 and then just save out at 2.2

[Dave Buckley]

also the bottom 2 images in that series of 4 is how it looks in the vray frame buffer

[Stephen Thomas]

In your max gamma settings the input should be set to 2.2 since textures will most likely have been created in gamma corrected colour space i.e. by eye on your monitor. If you are using the vray hdri map the gamma is automatically set to 1.0 for this map, there is no need to mess with the max gamma controls.

 

Output gamma I normally set to 2.2 as I always save my images as an 8-bit format i.e. jpeg or targa. On the rare occasions I save to exr, I override this to 1.0 in my file save dialogue.

 

Gamma correction should not be applied in the colour settings if you are trying to implement a linear workflow. However in the latest vray builds you should set it to 2.2 and check the adaption only box. This means that you are telling vray that a gamma correction is going to be applied when saving the image and it will do more sampling in the shadow areas to compensate for this.

[Dave Buckley]

so why would the gamma settings in the vray colour mapping ever be set to 2.2 as described here???

 

http://www.aversis.be/tutorials/vray/index.htm

 

is this not linear workflow

[Stephen Thomas]

He does suggest this as another option, though strictly speaking if you are applying a gamma correction during the rendering then no, it is not a linear workflow. Also things get confusing when you save out your image. Because the correction has already been applied you would need to save as a jpeg with a gamma setting of 1.0.

[Dave Buckley]

cheers so stef, so i guess its a case of either or really, all i want is for when i open the image in photoshop, it looks like it did in the vray frame buffer, which in this case is what happened with my bottom 2 images.

 

thats how they looked in the frame buffer also.

 

i think tho that i have achieved better results when applying the gamma correction at render time through the colour mapping as you can see there is more noise when the gamma correction has been applied afterwards at the time of saving

 

but i think you have answered my question anyway stef, cheers

[Dave Buckley]

just tried the gamma adaptation checkbox, when opened in photoshop it still doesn't look like it does in the vray frame buffer however it isn't as washed out

[Dave Buckley]

and i'm guessing that the workflow on the aversis tutorials would be a case of saving the image out as jpeg with a gamma of 1 as he doesn't explain it that far but i'm guessing thats what he does.

 

so i think i'm going to opt for a gamma of 2.2 and then saving as tif with output gamma value of 1.

 

i guess this is correct in a way.

 

its exactly the same as rendering with vray colour mapping gamma set at 1, and then saving out as tif with output gamma of 2.2

 

my results in my first post show that these do the same thing, but the result is smoother when adding the gamma correction at rendertime through the colour mapping.

 

sorry i'm doing a lot of repeating myself, but i'm just trying to help it sink in

[Dave Buckley]

However in the latest vray builds you should set it to 2.2 and check the adaption only box. quote]

 

If doing it that way, would you then save out with a gamma output of 1.0 or 2.2??

 

because when i tried doing it this way as you described i saved out as tif with gamma of 2.2 and it washed it out like in my first post

[Stephen Thomas]

Yeah, you can do it either way really, as long as you only apply the gamma correction once. The reason you get less noise when using colour mapping gamma is because the shadow areas are lighter and getting sampled more.

 

If, like I do, you keep your colour mapping linear and add the gamma correction when saving the image, you would tick the adaption only box so that vray doesn't apply the correction but still does the extra sampling.

[Dave Buckley]

ok so your saying have it as linear, light and dark 1 gamma 1 with adaptation checked, then save out as an 8bit file format jpeg/bitmap/tif etc with an output gamma of 2.2???

 

i think this is where i was going to end up

[Dave Buckley]

well i just tested that method and when opened in photoshop it still looks washed out.

 

in the vray frame buffer it looks really nice and crisp and clean like i want ti to look, this is with linear colour mapping at 1 for light dark and gamma and i want it to look like this when i open it in photoshop

 

sorry if your getting frustrated with me, i'l get it soon enough i promise, i just don't understand why i can't just save it as it is in the vray frame buffer and thats it

[Dave Buckley]

very very shamfully i think i found my problem

 

i wasn't using a vray camera in my tests, will this make a difference???

 

do i need to be using one if i am taking into account all this gamma stuff??

[Stephen Thomas]

Brainwave! Think I've figured out your problem, you're not using any textures in your scene are you? What you need to do is under the max gamma settings check the boxes for 'Affect colour selector' and 'affect material editor'. This means that your colour swatches will be linear as well and won't be washed out in the final image.

 

Also re: your previous post, my colour mapping settings are linear; light=1.0, dark=1.0; gamma=2.2; 'adaption only' checked. If you have the gamma set to 1.0 vray won't perform extra sampling in the shadow areas as I mentioned.

 

Hope this sorts it out for you!

[Stephen Thomas]

very very shamfully i think i found my problem

 

i wasn't using a vray camera in my tests, will this make a difference???

 

do i need to be using one if i am taking into account all this gamma stuff??

No you don't need to be using a vray camera, this is just about having max and vray set up to deal with your bitmaps and colours correctly to give you the correct output.

[Dave Buckley]

erm i was using vray materials and i already have the two checkboxes for the colour swatches checked.

 

hmm

 

i guess it may have been because i was just rendering the perspective views rather than through a camera.

 

and i think the problem with the older scenes that i was trying to render is that there textures may not have been run through the linear process when they were first created maybe???

 

with those settings that you have described, do you still save the output with 2.2 and also when you open the render up in photoshop ,does it look like the same as in the vray frame buffer

[Dave Buckley]

oh and i'm lighting using hdr only in gi evironment override only, you reckon this may have something to do with it

[Stephen Thomas]

This is all getting a little confusing! I've set up a simple test scene and attached a screen grab of my settings as well as the render saved from the frame buffer using default gamma. Both look the same. Try a similar scene with these settings and see what you get.

[Dave Buckley]

yeh i'm confused too as always with this whole rendering lark, see yours is doing exactly what i want mine to do. what format did you save to??

 

i have been saving to tif as i don't want to lose any quality

 

maybe my photoshop settings???

 

who knows

 

i'l do exactly the same test scene and see what my results are

 

oh how did you light this and is it through a camera

[Stephen Thomas]

Hey dude, it's friday - everyone's brain's a bit melted! No camera, just lit by default vray environment override. Saved to jpeg, but I sometimes save to targa or tif without any problems.

[Dave Buckley]

you are right it is friday, its my day off today and all i have been doing is learning vray determination for you that is

 

you can give yourself a big pat on the back for the help you have given me stef, but its amazing how the simplest things catch you out.

 

please don't hate me but i found my problem.

 

you know on the vray frame buffer itself

 

i didn't have the sRGB button depressed.

 

that has now leiminated my problem.

 

just to confirm, that sRGB button should be pressed in at all times right???

 

but i don't know why

[Stephen Thomas]

you are right it is friday, its my day off today and all i have been doing is learning vray determination for you that is

 

you can give yourself a big pat on the back for the help you have given me stef, but its amazing how the simplest things catch you out.

 

please don't hate me but i found my problem.

 

you know on the vray frame buffer itself

 

i didn't have the sRGB button depressed.

 

that has now leiminated my problem.

 

just to confirm, that sRGB button should be pressed in at all times right???

 

but i don't know why

The sRGB button on the frame buffer is just a preview button to show you what the render will look like once the gamma correction is applied to the saved image. If however you are applying the correction in your colour mapping settings, i.e. gamma=2.2 and 'adaption only' off, and not when saving the image, then having the sRGB button off is the correct thing to do.

[Dave Buckley]

ok everything is clear again now, cheers for the help, i was doing a mix of both technically hence why i was getting confused.

 

well at least my one jumbled mess has now become to clear messes

 

cheers again stef.

 

i'm gonna bookmark this post to save further confusion

 

i guess i could hve just altered in photoshop to look like the frame buffer but that takes the fun out of vray's learning curve

[Dave Buckley]

last question is . . .

 

colour mapping gamma 2.2, adaptation on, sRGB on, output gamma 2.2

 

AND

 

colour mapping gamma 1 adaptation off sRGB on, output gamma 2.2

 

are technically the same

 

AND

 

colour mapping gamma 2.2, adaptation off, sRGB off, output gamma 1.0

 

is also technically the same assuming that the settings in Max preferences are set at 2.2 with the input gamma at 2.2????