Specify Focus changes brightness massiv

[Komposer]

Hi,
Im playing around with physical camera.
Vray2, 2.004.

There is a big difference in brightness between specify focus on and off.
As u can see - DOF is disabled.

Could this be normal or is it a bug?
For me its strange.

Cheers

[t.petrov]

Hi,

Can you send us the scene or another simpler scene, so we can check if it is a bug or a feature?
You can attach the scene here in the forum or you can send it to vraymaya@chaosgroup.com

/Teodor

[Komposer]

I´ll do that.
thanks

[Komposer]

hi Teodor,

I sent a simpified scene to vraymaya....
I don´t know why, but the difference between ON an OFF is now much smaller than I send as image yeasterday.
But there is a difference!
Hmmm...

Perhaps you can explane me another thing in physical cam!?

When I set Specify FOV to default - to OFF...
Then I define Focal lenght to 34 (gate is default 36)...
The FOV slider now shows a value from ca. 54 !

Then I switch on SpecifyFocus with a value from 20 (which is the pefect distance for focus)...
In this moment, the camera zooms into the scene...
(I dont whant that but it happens)
The FOV value automaticly jumps to ca 47,5!
When I switch off SpecFoc, the cam zooms back a bit but not where it started!
Now FOV value is ca 48,5 - not 54 as it beginns.

I´m not able to understand this and I can´t find anything which helps me to understand these mystery things.

The only way for me working with phys cam is, to set Specify FOV to Specify...
Then I can set Focus distance without automaticly changing the zoom of my camera...

But FOV isn´t the same as foacal lenght....
What is the right FOV when I whant to use a 55mm standart optic?

I hope to get some clearing hints from You.

Thanks,
Jörg

[VI_MOVE]

I've noticed the same strange brightness behavior in Vray for 3ds Max as well, as posted in this thread:
http://www.chaosgroup.com/forums/vbu...732#post450732

[vlado]

I think it may be a slightly different issue - your problem was with the "specify focus" parameter, not "specify fov"

Best regards,
Vlado

[Zdravko]

I don´t know why, but the difference between ON an OFF is now much smaller than I send as image yeasterday.
But there is a difference!

We added your issue to our "to do" list.

Then I switch on SpecifyFocus with a value from 20 (which is the pefect distance for focus)...
In this moment, the camera zooms into the scene...

This is expected, actually this is how the real cameras are acting.
When you change the focus the FOV is also affected.

But FOV isn´t the same as foacal lenght....
What is the right FOV when I whant to use a 55mm standart optic?

If you want to simulate a real camera you don't need to take into account the FOV, instead use only real camera parameters as focus distance, focal length, F-stop, etc and turn off Specify FOV.