HDR/EXR lighting setup - Overbright results

[Jcaddy]

I've followed Peter Guthrie's tutorials on setting up a scene using his HDRI files (which I am using) and my scene is constantly over bright. He recommends using a value of 1.0 as your starting point in the output of the map as well as the strength of the light source and he gets great results....for me, I have to compensate the exposure as well as the values (.005) to get, what seems to me, a very incorrect result.

This is one of those things that I have used in Mental Ray before and it works very easily, but with VRay I have had very little success throughout my tests.

Below are some images of what is going on and the settings that I am using.

My setup is as follows:
-VRay physical camera
-VRay light set to be a dome with Peter Guthrie's high resolution sky in the texture slot.
-The texture is set to environment and spherical environment mapping
-Camera settings - F4, ss200, ISO100

Can anyone help or maybe point out if I am missing one small step to get this to work properly?
Thanks!

[Jcaddy]

I forgot to ask if units have anything to do with the way that the values might effect the scene? For instance, Peter is probably working with meters, correct? If I'm following his tutorial in feet, should I be calculating the difference between the two in order to use it properly? Or should a generic value of 1.0 in the output of the map be sufficient no matter what the units are set at?

[Distorted_Imagery]

Hi Jcaddy,

Looking at your settings it will be your Camera settings, Try raising your F number (4 being a bit low as I tend to use that in low light condtions) and use possibly 16 or 8.

You should notice an imediate change

[Jcaddy]

Thanks for the quick reply. I ran tests with F8, F16, and F32 all of which got darker of course, but they still don't render properly. Blotchy and overbright...

Is there some obvious setting that I am missing when using the Vray dome light?

[Distorted_Imagery]

Thanks for the quick reply. I ran tests with F8, F16, and F32 all of which got darker of course, but they still don't render properly. Blotchy and overbright...

Is there some obvious setting that I am missing when using the Vray dome light?

No worries, are using a vrayhdr map or are you using the bitmap loader, also do you have anything assigned in the vray environment override?

I personally would use the vrayhdr map and nothing in the overrides, another thing could be your ir settings are too low, so try just the standard 50 hsph an 20 interpolation samples on a medium preset.

[Jcaddy]

I was using the bitmap loader but i'll give the HDR map a shot and see if that helps. Thanks again!

[Jcaddy]

Does the target radius and emit radius on the vray dome have any effect on the scene? How about the check box for spherical (full dome) ?

[Jcaddy]

Alright, so here is the result when taking the output value of peter's sky to .001 and upping my Fnumber to 16. It renders correctly but seems so unnatural to have to knock a value down that low, right?

[pg1]

is your dome light set to a value of 1?
it defaults to a value of 30 when you first make it.

[jacksc02]

your shutter speed of 200 is fairly low. If its a bright sunny day with a clear sky a shutter speed of around 1600-2000 is probably closer to reality if you are using an F-stop of 5.6

[Pictor2]

I've had a similar problem to this too since switching to Max 2010. A scene with a similar setup to how Peter does it worked fine in Max 2009 but went splotchy and overbright in 2010 even though the settings were the same. I supect it's something to do with .exr format because converting it to a .hdr in photoshop solved the problem. Haven't got time to investigate further at the moment but in the meantime try converting it to a .hdr and see if that helps.

[peterguthrie]

this seems strange, can you email me your test scene? Or tell me which sky you are using and I'll make a quick scene and share it here

[peterguthrie]

what version of max are you using?

I know some people have had issues with max's handling of exr files

try using the hdr instead and see if it works

[Jcaddy]

Hey everyone, thanks for the replies.

Peter - I'm using 1123 Sun Clouds and Max 2010 with all service packs / productivity plugins installed. Attached is my test scene without the EXR in question so that I am not giving your skies out to everyone for free

Chris J - I've tried just about every setting with the camera, and when I finally decided to set the output value on the exr to .001 they seemed to make sense.

From here, I've tried running Max in metric mode rather than inches, but that seems to do absolutely nothing different.

Any other ideas?

[rivoli]

I know some people have had issues with max's handling of exr files

as peter says, max's exr loader can cause problems. try to convert the exr in hdr and load it via the vrayhdr map.