White spots when using LWF (Linear workflow)!!

[JayTee]

Hi,

 

I have used LWF for a short while and almost every scene I render I get these white spots with black outlines around bright areas.

 

Using clamp output takes care of the spots, but I don´t want to use clamp because the main reason I am using LWF is to get better exposure control in post production. So what am I doing wrong?? and is there any solution to this problem or is it better to go back to regular way of doing things? Please help!

 

I render with Vray 1.5 SP5. I use Vray frame buffer and save as EXR. I use normal cameras. Here are the setting I use:[ATTACH=CONFIG]43429[/ATTACH]

 

[ATTACH=CONFIG]43426[/ATTACH][ATTACH=CONFIG]43427[/ATTACH]

Edited June 22, 2011 by JayTee

[Nic H]

to fully sample those areas and get rid of the 'overbright spots' you will need very very high antialiasing - like almost universal settings (1/100 DMC, 0.005 etc..plus a non sharpening filter)

 

tbh no one will be able to tell if you have clamp output / subpixel on - it wont make a visible difference

use the 16bit range to be able to adjust your exposure and colours without banding and done worry about the overbright spots imo

 

we dont bother with that - other than a qucik few tests we did whcih realised no benefit for what we do plus much longer rendertimes

[JayTee]

Thank you so much for a quick reply!

 

So do I just select save as 16bit TIFF and clamp output? Do I have to change some other settings too? (to burn gamma to the image or something..)

[JayTee]

Can somebody explain me what this "Clamp output" really does?

 

I ask this because I rendered a Linear workflow 32bit EXR-image with Clamp output selected. I compared the clamped image and non-clamped in photoshop. I played around with exposure control and I saw no difference between the images. Only difference was that the clamped version didn´t have these white overexposed dots.

 

I thought selecting "clamp output" turns the colors to 8bit mode, but when I checked what mode was on in photoshop it turned out to be 32bit still?

[Jan]

the image still in 32 bit (you save it as exr 32 bit), but you lost any information above the clamp value (usually 1). In other words, in your image you will not differentiate the intensity of a 100w light from sunlight

Edited June 22, 2011 by Jan

[notamondayfan]

If you set clamp output to say 10 it will give you some control in post, so long as your render is some what already balanced.

 

Also, change your AA filter, its a sharpening filter so will exaggerate edges. Try something really soft like Area, and see what happens. I generally use the VraySync filter as it works in most cases.

[JayTee]

Thanks again for the answers! I will give them a try.

[archigem]

Thanks again for the answers! I will give them a try.

 

Hi Jussi, did u get what u wanted? I am also facing the same problem... and now I m trying to improve the things.. :-)

 

 

After changing the filter to area from catmull-Rom.. the problem is solved.. :-) thanks everybody.

Edited June 30, 2011 by archigem