Accurate Light Intensity & Camera Exposure (pdf tutorial)

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JQL
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Thanks for the tutorial Patrick!

For some time I have some comments on how exposure works in Thea. It's a bit confusing specially for beginners, and for people used to photography it seems crippled until we find out that the settings in two different places affect different stuff.

Unless those visual features like grain and dof would be able to be controled on those Darkroom sliders dynamically, I'd like to be able to turn them 3 into a single exposure slider for easiness of use. This would be particularly useful for beginners.

Sometimes I don't see the sense of having those 3 camera related exposure controls, as they all do the same thing. They are good for fine tuning each other, but people do tend to get lost and a direct way would be intuitive for people who know not much about photography. For those who do though, the idea of loosing control, is not good, but this could be fixed with an advanced exposure toggle or checkbox that would make the 3 settings available again.

I also honestly don't see the point of having the 3 settings on two places (camera settings and darkroom) unless there would be a way of binding those values between render settings and darkroom. Changes in one would affect the other and this would really help us get realistic results by default and it would be easier to create DOF effects (and possibly some fake grain).

This would truly make Thea realistic but if we would want to override the values for "artistic sake", there could exist a checkbox for that or a lock icon so we could break the relation between darkroom and studio.

I would personally love if thea would be able to focus dynamically as we are rendering if we'd use f-n. Would it be doable?

I know we can create fake DOF with a pinhole rendering, a depth mask, and blur, on post pro, but Thea's blur is a different kind.

So I'm imagining DOF, could be used on Darkroom, with some accurate post-pro method, over the base render, wich would be faster to render if it would be rendered in Pinhole as Thea wouldn't have to calculate blur at render stage. It could work as vignetting or glare wich give way more realistic results than traditional post pro methods.

It would also be cool if this DOF could be saved into a movie like relight.
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Hi JQL

I am sure we will revisit exposure for Thea and see how we can make it more elegant. but the reason we have the exposure setting split is because if you where to create DOF or Motion blur,
you would also affect the exposure at the same time and this can get frustrating. imagine you just want to ad a bit of dof but doing so your image get lighter or darker.
the only way I see for the moment is to have some kind of "Auto" switch that binds shutter speed and f number in a way that when you alter one, the other adapts to always keep the same exposure. we may also add some kind of "simple" exposure slider for beginners inside the darkroom.
about post pro Dof ... I am not so sure if we are going to spend effort on that as there are other areas in Thea we would like to concentrate our forces. but who knows, maybe in the future :)

now ... if you just copy past the exposure settings from one place to the other, you get exactly what you would get with a real camera. so ones you have a good exposure, just copy past your settings to the camera properties panel.
I would personally love if thea would be able to focus dynamically as we are rendering if we'd use f-n. Would it be doable?
this should be possible right now using interactive render and the focus tool or auto focus.
I know we can create fake DOF with a pinhole rendering, a depth mask, and blur, on post pro, but Thea's blur is a different kind.
Thea's blur is a different kind as its the real thing which you can not "fake" with post pro.
the post pro version with z depth map has known limitations like its unable to create correct DOF when transparent objects like glass are present and other important limitations.

Greetings Patrick
" Poets say science takes away from the beauty of the stars - mere globs of gas atoms.
I too, can see the stars on a desert night, and feel them. But do I see less or more ? "

Richard P. Feynman
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JQL
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patricks wrote: about post pro Dof ... I am not so sure if we are going to spend effort on that as there are other areas in Thea we would like to concentrate our forces. but who knows, maybe in the future :)


That would be nice. Though I also think there would be things more important. We have DOF already after all.
now ... if you just copy past the exposure settings from one place to the other, you get exactly what you would get with a real camera. so ones you have a good exposure, just copy past your settings to the camera properties panel.
That is the sort of manual labour I think software should automate... hence the lock/toggle/auto question.
I would personally love if thea would be able to focus dynamically as we are rendering if we'd use f-n. Would it be doable?
this should be possible right now using interactive render and the focus tool or auto focus.
That restarts render.
I know we can create fake DOF with a pinhole rendering, a depth mask, and blur, on post pro, but Thea's blur is a different kind.
Thea's blur is a different kind as its the real thing which you can not "fake" with post pro.
the post pro version with z depth map has known limitations like its unable to create correct DOF when transparent objects like glass are present and other important limitations.

Greetings Patrick
Maybe with a combo of other channels it could be done fairly better than with the traditional basic post pro dof workflow...
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patricks
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there exist no way to do 100% accurate dof in post pro and that's also why Thea has to restart when changing dof in interactive render. even one of the best post pro tools for dof can not do it correctly and has the common issues (its probably the best plugin you can buy for post pro dof). read the Issue section at their page ;)

http://www.frischluft.com/lenscare/


Greetings Patrick
" Poets say science takes away from the beauty of the stars - mere globs of gas atoms.
I too, can see the stars on a desert night, and feel them. But do I see less or more ? "

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JQL
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You are a perfectionist Patrick...:D

I wouldn't mind keeping our current real DOF and also have a lousy fake and inaccurate yet better than what I can achieve with my post pro workflow and inside darkroom, DOF for fast results and control or even animations.

This makes me think of AO. If you consider AO it is a fake way of simulating light and shadow, yet Thea is using it. That is the same kind of philosophy we could use with an optional fake interactive DOF. It would never be as accurate as the real deal, but it surely would be very handy sometimes...
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saurus
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Thank you fot the tutorial.
To make it short, the process could be explaned in 3 steps:
1 DOF UP - setting f-number DOWN. Fixed.
2 Motion blur UP - Shutter speed number DOWN. Fixed.
3 Adjust exposer with ISO value. Fixed.
...
4 A button to lock the exposer could be introdused here. Fixed.

Is this ok?
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jc4d
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Such a great reading, thank you. :thumbup:
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patricks
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spot on saurus! :)

another thing I wanted to add ... if you use real light values, then the exposure settings you use will always be right. I mean if you adjust the exposure setting until you see your scene nicely exposed, this settings will be correct if you keep the values in realistic camera values (for example don't use ISO settings above 6400 and keep them more at 800 and lower as this is what a real camera would use). you could use those settings later with a real camera and would get a good exposure with similar light setup. or the other way around... you can use real camera settings you used for taking a photo and then try to recreate a similar light setup in Thea and it should work.

Greetings Patrick
" Poets say science takes away from the beauty of the stars - mere globs of gas atoms.
I too, can see the stars on a desert night, and feel them. But do I see less or more ? "

Richard P. Feynman
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JQL
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Patrick,

There's a scenario that hasn't been covered up with this pdf:

You have a material for light fixtures at 60W.
You have 10 light fixtures created with a square of 0.1m2 and that material instead of a point light/ies/spot light.
Those mesh lights are physically separated from each other. How will that work:

1 - As the mesh material is 60W it emitts 60W total. Will each of the 10 light fixtures emit only 6W?
2 - As point point or spot lights are not possible to insert into proxies, the only way we have to insert lights inside proxies is with mesh lights. So what if those light fixtures are inserted as proxies? Will each of them emit only 6W also?

That seems to also be a recurrent issue around here that could be interesting to explain along with the simple and effective mesh light explanation you there.
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patricks
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JQL wrote:Patrick,

There's a scenario that hasn't been covered up with this pdf:

You have a material for light fixtures at 60W.
You have 10 light fixtures created with a square of 0.1m2 and that material instead of a point light/ies/spot light.
Those mesh lights are physically separated from each other. How will that work:

1 - As the mesh material is 60W it emitts 60W total. Will each of the 10 light fixtures emit only 6W?
2 - As point point or spot lights are not possible to insert into proxies, the only way we have to insert lights inside proxies is with mesh lights. So what if those light fixtures are inserted as proxies? Will each of them emit only 6W also?

That seems to also be a recurrent issue around here that could be interesting to explain along with the simple and effective mesh light explanation you there.
I am about to finish a tutorial that will cover this ;)

Greetings Patrick
" Poets say science takes away from the beauty of the stars - mere globs of gas atoms.
I too, can see the stars on a desert night, and feel them. But do I see less or more ? "

Richard P. Feynman
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