Auto exposure like real consumer physical camera

[fraggle]

I wondering why there is no auto exposure in vray? Even the most basic and cheapest physical camera make perfect photography from the first shoot, even in very difficult lighting situation!
It takes really to long to set up vray when looking for the right vray physical parameters (infinite number of try consume a lot of hours).
So a feature that allow to get the right exposure in a single click will be a must.
Thanks

[joconnell]

You'd almost have to do a pre render to get your levels, then a second render afterwards for the proper frame. If you let every frame auto expose like a dslr, you'd end up with lots of very flickery exposure changes per frame and you'd have to stabilize it in post. Better off rendering a really low res, low quality sequence first and finding the extreme points, then animating your exposure between each of the appropriate settings.

[JezUK]

I used to think this would be neat, but don't suffer this problem at all anymore. What tipped things in my favour was a) really understanding how VRay works, understanding that it is trying very hard to mimic reality, so the user also must understand 'reality' as well and b) coming from a traditional photographic background.

There are only 3 types of lighting I'm ever interested in;

Exterior, Interior and Studio.

Exterior, there is Kodak's "Sunny 16's Rule" (for ISO 100, on a bright, clear sunny day with sun on your back and shutter 1/100, use f/16).

Interior, f/8, 1/50.

Studio, f/8, 1/10.

That's it and your starting point.

Where people get confused (in my experience) is that they don't understand or are aware of what an f-stop in terms of exposure is, i.e. one full stop equals halving or doubling the amount of light in the exposure.

Furthermore, a lot of people aren't aware of the traditional camera shutter speeds / apertures (1/30, 1/60, 1/125, 1/250, 1/500 etc, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f16). These numbers all have a significance with regards to a FULL STOP of light.

FAO VLADO;

What I'd MUCH rather prefer to have in V-Ray Physical Camera ARE these ACTUAL shutter speed and aperture numbers, rather than an ability to spin through anything and which is stepless - this will help us all so, so much more (in fact I'll ask if Vlado can add this idea as I think it's really worth having).

At least a checkbox in V-Ray Physical Camera to enable/disable traditional shutter speeds/apertures like those I've listed above) which could be further enhanced with either 2 more checkboxes, 1) to allow 1/2 stop increments and another to allow 1/3 stop increments or better still a dropdown allowing for 'steps' (i.e. full, 1/2, 1/3).

[tsvetan.geshev]

Hello fraggle,

For faster exposure setups you can override all your scene materials and use V-Ray RT for instant feedback.

Real world cameras have few different modes of metering the lighting, for example they have matrix /which is measurement of the lightness of the entire frame/ and spot /which is metering the lighting in specific spot/. These spots are autofocus points.
Our camera does not have focus points, also adding all this things will confuse even more users.

Let's imagine this situation, you have dark background and small object, that is lithen with spot light, if you use matrix metering you object will appear overbright, because the bigger part of your frame will be dark and V-Ray will try to compensate, so you
need to use spot metering. There are lot more lighting situation, that will require some understanding, so I think the settings of our camera for the moment are quite good blend of capability and user friendliness.

[fraggle]

Well, from an architect point of view and not a 3D artist point of view, when I have to shoot something to add it into a presentation, I just pickup the iphone and snap it. 99% of the time, whatever the lighting situation, the result is more than acceptable to be added into the presentation right away.
The point is: less time we spend on 3d, then more we can spend into creativity.

[JezUK]

Fraggle,

You can't approach the world of 3ds Max / V-Ray with the automation of an iPhone. Nice idea but the possibilities with our software are too huge.

I'll re-iterate (for your benefit) - if you really want to understand what's going on and not, in your words, use an "infinite number of try consume a lot of hours", you really need to have a grasp of photography and photographic principles. See my above post and you'll not be consuming more than a couple of minutes at the very most.

[snivlem]

Even the most basic and cheapest physical camera make perfect photography from the first shoot, even in very difficult lighting situation!
Thanks

Most photographers in arch viz will bracket because no camera in the world has decent dynamic range - they all suck.

The best way in V-Ray is to render 32bit float then tonemap in post which WILL make perfect exposure. I think V-Ray's tonemapping is not as powerful and is destructive unlike doing this in post. Maybe if V-Ray had a realtime tonemapper that would be awesome.

[glorybound]

I know you f-stop up and f-stop down; then merge them, but what is an f-stop in Photoshop? Or, do you just eye it?

Most photographers in arch viz will bracket because no camera in the world has decent dynamic range - they all suck.

The best way in V-Ray is to render 32bit float then tonemap in post which WILL make perfect exposure. I think V-Ray's tonemapping is not as powerful and is destructive unlike doing this in post. Maybe if V-Ray had a realtime tonemapper that would be awesome.

[snivlem]

I know you f-stop up and f-stop down; then merge them, but what is an f-stop in Photoshop? Or, do you just eye it?

In lightroom/photoshop they have a tool called exposure (in photoshop it is an adjustment layer/adjustment tool). It seems to be accurate in terms of a positive adjustment of 1 = 1 stop.

I tried once with a camera (taking a standard shot, then a shot overexposed by 1 stop) and the camera pretty much exactly matched photoshop/lightroom with an increase of 1 stop.

[samuel_bubat]

Most photographers in arch viz will bracket because no camera in the world has decent dynamic range - they all suck.

The best way in V-Ray is to render 32bit float then tonemap in post which WILL make perfect exposure. I think V-Ray's tonemapping is not as powerful and is destructive unlike doing this in post. Maybe if V-Ray had a realtime tonemapper that would be awesome.

They don´t suck, that how realworld works I used to do exposure in post but stopped because for every shader fine tuning you´ll need to save your image and open it in whatever software you use to make your color correction. Also when you use the Vray internal tonemapping like reinhard Vray knows in advance how bright your image will be and accordingly samples the scene much better.

[snivlem]

They don´t suck, that how realworld works I used to do exposure in post but stopped because for every shader fine tuning you´ll need to save your image and open it in whatever software you use to make your color correction. Also when you use the Vray internal tonemapping like reinhard Vray knows in advance how bright your image will be and accordingly samples the scene much better.

Of course. Probably shouldn't have used that expression.
What I mean is that if you take a photograph you only get a few stops to play with.

With vray you can render without tonemap and (in Maya) you can adjust slider so you get an unreal amount of fstops to like -10 and probably more. What I mean that instead of tonemapping in post like Photoshop, it would be sweet to have a tonemapper that is adjustable in the framebuffer which is a bit more real time than doing in post. Something like random control's.

[3LP]

If I'm not mistaken, you do have that option in the Vray VFB for a long time, or am I not understand you correctly.



Of course you should not use this exposure (although you technically could) for final renders as you should expose your camera the closest to what you will end up using, this is the best way to ensure you maximize the sampling process Vray will use to determine the noise.

IE : If you render completely blown out or underexpose and expose in post, chances are you will end up with a higher render-time than if you exposed it correctly in the first place.

I use the exposure slider to determine what exposure I should have once I trowed a light in the scene and then replicate that in my cam, and never touch it again after. A 3 minute task, and with RT, it's even faster, but I agree that a auto button would be great.

Back in the days, I was using lele matrix exposimeter.
http://www.scriptspot.com/3ds-max/sc...les-vray-tools
It works as a real cam exposimeter. It renders out a preview to calculate the exposure (and white balance if you wish so) and applies it to your cam.

Stan

[glorybound]

Also, Solid Rocks has the exposure control, although I never used it.

[3LP]

Yep I guess so but haven't found the need to buy it as I rather understand vray myself.
I wouldn't by solid rock if it's only for the exposure then

[glorybound]

I enjoyed Solid Rocks, but learned more from VRay's Quick Settings. SR changed almost everything to really wonky variables.