Making sense of exposure...

[benjamin9999]

...meaning, can anyone?

There's no shutter speed, and I assume f-stop, ISO, and 'exposure' are all just accumulated into the same multiplier, or very similar.

I wonder about:

Why is the Linear/Off response-curve so much darker than any profile - I'd guess that any of those curves would create their effect by reduction, not amplification.

Why are material preview scenes so bright? If I adjust exposure for them then my scene is underexposed by 4 stops at least, even in daylight.

Is there any reason for the daylight environment to have a power > 1.0 ? (Assuming one isn't trying to render a scene on another planet)

Since the material preview scene was made by OR-team, I assume they know The Right Way. My exposure is usually something like Exp=1, ISO=200, f=2.8 -- which makes the material-preview scene blown out completely -- I assume they would not intend for users to adjust their camera when flipping between a scene and a preview, or how useful would they be.


And if each of those factors are just multiplied together, then what reason is there to have all three? Maybe I should just set ISO=1, f=1(or whatever gets x1.0 as it's inverse) and only adjust 'exposure.'

Discuss.

[matej]

Why are material preview scenes so bright? If I adjust exposure for them then my scene is underexposed by 4 stops at least, even in daylight.

As you said, this is especially annoying if you are setting your materials up on the ball and need to jump back & forth between the ball & actual scene. The reason its brighter is that the preview scene contains a fixed emitter, which lighting gets added to the environment lighting set by the user. Maybe we should have an option to toggle off this emitter. Anyway, I got accustomed to not use the ball at all, and just set the materials on the actual model.

About the tonemapping: I never touch ISO or fstop, just exposure, cause it seems to me that those parameters do exactly the same thing. But I don't have much photographic background, so this discrepancies with real photo camera settings never really bothered me.

[ROUBAL]

this is especially annoying if you are setting your materials up on the ball and need to jump back & forth between the ball & actual scene.

- For my own, I never use the ball as well. I prefer adjusting the material directly in the real scene.

- In an actual camera, the F-stop value has an effect on the depth of field. In Octane, it hasn't. Curiously, this parameter is adjusted by the Aperture slider... which has no effect on the brightness ! I already asked the reason why a long time a go, and I have to say that I don't remember the answer !

These two parameters must be adjusted separately to fake the proper setting. It may allow more flexibility/control from an artistic point of view, but doesn't match the behaviour of an actual hardware camera.

[benjamin9999]

Well, I've been experimenting some more.

I built my room piece by piece, roof last...

Trying to imagine what the space would look like (given the same exposure settings in a camera) when the roof was removed in the summer - and I decided that the Daylight Environment must not be calibrated to 1.0 ? Or maybe it isn't even expected to be a physical reference in that way.

If I push the d.env power up to 30-40 then I feel like I get the intensity I'd expect in real life.

Put another way:
A small 40w tungsten bulb, uplighting an interior wall would be barely noticeable in daylight, but this isn't the case until d.env is at those levels.

I originally assumed that 1.0 was a calibrated value of some kind.

I thought to mess with it after loading my scene in the Thea Render demo and noticed right away that sunlight entering the space was far more intense than in Octane.

[pixelrush]

>Aperture in Octane is f-stop/DOF.
Something that has always seemed to me quite odd or incorrect in the way its done.
I think this should be changed to be logical for those who are familiar with cameras.
The aperture and f-stop should be realistically linked/combined.
If people don't want to balance/trade off playing with ISO/shutter etc as they would with a real camera then it should be simplified ie f-stop should be the DOF control and the other stuff removed.
If people do want to play photographer then they should add shutter and make everything work as expected.
IMHO

[benjamin9999]

It may be coincidence, but....

With the Day-Env power @ 100.0, it seems to me that everything works in a reasonable way.

For example - The Sunny-16 Rule "works" @ f/16, ISO 100, Exp=1.0 ....

...and the difference between interior & exterior (and lighting) all seems much more like I would expect.


Maybe it's all been handled very well by the developers and it's just a documentation failure. (although, the default Day-Env is initialized at 1.0... perhaps there is a pwr/=100.0f; that needs to be removed somewhere)