Author Topic: AUTO-Exposure please!  (Read 8179 times)

2016-09-09, 17:05:48

tony_morev

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VERY handy when it comes to complex fly through animations, when camera travels through areas of different lighting

Insight render had it :)

super simple
1) pre-render a frame at a set low res and arrive at a average exposure number, before rendering production size and quality
2) give users a multiplier to manipulate the resulting desired EV up or down
3) to prevent flickering in the animation pre-render (-2, current, +2 frames) and average the EV value out

there may be a smarter way of doing it, but that's how it was handled in Insight, and worked like a charm

thank you!

PS there's always a chance that i'm missing something, and there's already a way to accomplish autoexposure, in which case please point me in the right direction
 

2016-10-03, 16:42:35
Reply #1

Ondra

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Sorry, it does not seem to be that useful, compared to the relative complexity it would take (prerendering animation at low res), so we will not implement it
Rendering is magic.
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2016-10-14, 19:14:05
Reply #2

tony_morev

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may be there is a smarter way to do it? i just gave you a brute force approach

right now there is no easy way to control exposure if the camera travels through areas of drastically different lighting conditions, say between lit and unlit spaces or exterior to interior

manual animation of exposure will never look right and is a paint to set up

2016-10-14, 20:50:25
Reply #3

lolec

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There might be a way to adjust exposure dynamically for animation, the same way Timelapse triggers (who don't know the future) adjust exposure dynamically.

It's called automatic BULB RAMP, in real life photography we change the exposure time over time, and the only way to do that easily is to set the camera into BULB mode and let the trigger control the exposure time by how long in presses the shutter, anyway, that's why it's called BULB RAMP. Of course corona could much easily change the exposure.

Here is an example of a sunset simulator and how the automatic BULB RAMP feature adapts over time. http://firmware.timelapseplus.com/sunset/

This will only require to look an the previous rendered frames, and adapt future exposure slightly over time using a PID filter.

2016-10-14, 20:56:33
Reply #4

lolec

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http://www.timelapseplus.com/blog/2014/10/1/firmware-20141001-released

look at the video of the sky here to see how well this approach works.




2016-10-14, 21:41:54
Reply #5

tony_morev

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well, the real cameras have an advantage of metering before taking a shot
obviously for a rendering engine to "meter" it would have to generate a preview of a sort, even if strictly internally

that's why, i think, Ondra is dismissing it as complicated

but, the size of that preview can be very small and there is no need for AA
considering the sheer speed of corona even on heavy scenes it's a shame not to take advantage of it

even max itself has an option of auto-exposure, albeit not supported by Corona, let alone any real photo and video camera

it seems odd that developers are inclined to bring in all the complicated settings of real wold cameras letting out the convince features

ever tried shooting a non-stationary video with locked exposure? probably not, because it'll be garbage :)

2016-10-14, 22:50:40
Reply #6

lolec

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I'll be the first to admit that I'm not an expert on how Corona works, but if I'm able to change the exposure while it's rendering, shouldn't Corona be able to do the same ?

Also, if you are rendering a video, you don't want abrupt changes in exposure, so even if you transition from a dark place to a very bright one ( getting out of a tunnel ) It would be acceptable for Corona to take some time to get used to it. I don't think a 1 frame delay is a big deal, but as I said, Maybe exposure can be set just before saving.


2016-10-18, 00:02:50
Reply #7

tony_morev

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there should be a separate section for DENIED feature requests :)
cause this is hardly RESOLVED

2018-05-27, 04:32:47
Reply #8

JViz

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Sorry, it does not seem to be that useful, compared to the relative complexity it would take (prerendering animation at low res), so we will not implement it

Vray next got it now. AND auto white balance.
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2018-05-27, 10:24:05
Reply #9

Dionysios.TS

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Sorry, it does not seem to be that useful, compared to the relative complexity it would take (prerendering animation at low res), so we will not implement it

Vray next got it now. AND auto white balance.

Auto White Balance and Auto Exposure are completely 2 different things. The first one is easier to do, Photoshop does it, Lightroom as well and even better. The second one is more difficult and I understand the complexity.
Personally I prefer the White Balance to be done manually in post production, much more professional move and more control.
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2018-05-27, 16:42:43
Reply #10

Jpjapers

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I can totally see the need for this for animations...

2018-05-28, 01:17:22
Reply #11

peterguthrie

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one of the joys of Corona is that you can just tweak the exposure once you have started rendering, so no need to try to guess the EV level like in Vray. For animations perhaps, but normally I'd just quickly check it using interactive and then keyframe the camera exposure.

2018-05-28, 10:26:22
Reply #12

romullus

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I can totally see the need for this for animations...
I can totally see how hundreds of hours of rendering goes in to a bin, if something goes wrong with either AE or AWB or both of them :] Both features could be nice for still images, but i'm not sure if i would dare to use them on animations.
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2018-05-28, 11:30:33
Reply #13

Jpjapers

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one of the joys of Corona is that you can just tweak the exposure once you have started rendering, so no need to try to guess the EV level like in Vray. For animations perhaps, but normally I'd just quickly check it using interactive and then keyframe the camera exposure.

My bad I misunderstood. I thought OP was saying that the corona camera EV wasn't keyframeable. My bad!

2018-05-28, 14:13:03
Reply #14

maru

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We have manual white balance in the vfb by the way. It's a bit hidden, but I am sure it will be properly exposed after the VFB ui overhaul in v3.
See: https://coronarenderer.freshdesk.com/support/solutions/articles/12000039650

I saw a video showing V-Ray's auto exposure, and I think it makes sense in many cases (especially in animations where the camera moves between interior and exterior). I am sure we can expect it in Corona soon as well.