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Over light then drop in post or light as is?


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#1 Gene Sung

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Posted 21 January 2015 - 11:45 AM

Hello everyone,

 

I wanted to see how you guys would approach creating a low light look. The camera is a Sony FS7, which has pretty good low light. This is just a test shot of my wife sitting on a couch as I was going through settings and testing the camera.

 

I just pointed a 1K open face, scrim’d down 1 stop with a silk in front to diffuse. The camera is at f2, native ISO of 2000

 

If you guys were trying to create a low light look, would you guys OVER LIGHT it like I did in the top picture? Or would you just try to create the low light look in camera?

 

I noticed on most cameras I’ve used, when there is not enough light there tends to be a lot of noise, so lately I’ve been over lighting and just pulling down in post. I’m able to get it very, very close to what it would look like if it had been lit for the finished look. 

 

How would you guys approach this? Over light a bit then pull down? Or just go for the actual look (and maybe a bit more noise)?

 

Thanks!

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  • beforeafter02.jpg

Edited by Gene Sung, 21 January 2015 - 11:46 AM.

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#2 Gene Sung

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Posted 21 January 2015 - 11:49 AM

FYI, the post time for something like this is very quick. Maybe takes about 1-2 minutes to pull the shot down, so post time isn't a huge issue.


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#3 Albion Hockney

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Posted 21 January 2015 - 12:03 PM

I think one thing that is throwing you off is that you are looking at a log picture as reference. Log is not supposed to be used as a repersenation of your final image ....generally because log images are so flat they appear much brighter and more milky then your final image.

 

so with that said I think your first image is "darker" then you think the underexposed parts of the frame are just lifted a lot. your final image appears pulled down a bit, but honestly it doesnt look far off from what it would be with a more standard curve applied to it.

 

When shooting on cameras that does LOG or RAW I generally look at LUT that has a curve that is closer to the final graded image and then I light for that. For example on the RED I will use "Red Gamma 3" with the knowledge that I have a bit more information then that in the raw. Some poeople use a "rec 709" curve and light for that when shooting log ....I find rec 709 too contrasty so I try to look at a LUT that is a little more wider ranged then that.

 

As far as the noise thing goes one thing you can do is shoot at a lower iso then native if you want really crisp shadow detail. this is similar to using more light and bring it down in post as you are basically overexposing when you drop the ISO. Every camera is different though I would run some tests with pushing the native iso of the camera with underexposure and see if it gets too noisy for you.

 

the last thing I would consider is that everything in images is viewed in relation to what else is there, but this I mean darker images usually appear dark because they are "low key" Meaning there is still bright parts of the frame that may read a stop or two over exposed but most of the image is below exposure. So if you want something to appear dark you may not want to just underexpose it but instead create contrast in your frame with the lighting


Edited by Albion Hockney, 21 January 2015 - 12:06 PM.

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#4 Tom Morrow

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Posted 21 January 2015 - 12:33 PM

I prefer the predictability of not over lighting. That way you see what you are getting in the camera. It really comes down to how much you want to work to avoid noise. When I was doing still photography I would over light and reduce in post to get fine art super low noise. With the camera on a tripod and static scene over lighting was just a matter of using a slower shutter.

But with video I don't because over lighting involves
- extra time for bigger lights
- easier to clip highlights
- lower dynamic range possible. If you are shooting a dark scene there is often a candle or flashlight or other bright light source in frame and not blowing that out may be more important than shadow noise.
Given that you only get one shot at the best performance with video I dont want to waste time obsessing with the waveform monitor.

It really comes down to your skill and trust of your end to end workflow. You can over light and get lower noise if you really have everything under control but I am not at that level.

Also reducing the lighting in post means you shift highlights that were in the nonlinear part of the curve down into the linear part of the output curve leading to more likelihood that things won't look the way they did on the camera monitor. If you are super knowledgeable about exposure curves you can work around or even straighten this out but for most folks easier not to try.
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#5 David Mullen ASC

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Posted 21 January 2015 - 05:19 PM

I think the term "over-lighting" is being used incorrectly here -- after all, there is just ONE light being used!  You take away that, and there would be NO lighting.  Just because you work at a higher level of illumination in order to use a lower ISO setting doesn't mean you are over-lighting.  Over-lighting is when you are using more lights than are needed to get the look you want, you've cluttered the scene with too many lights and there is often no contrast anymore to the scene and no directional feeling or sense of source to the light.

 

A single light would only be over-lighting a scene if it were being used to augment an on-camera practical source, but the added light was too bright and was clearly a second source, over-powering the on-camera source.


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#6 David Mullen ASC

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Posted 21 January 2015 - 05:31 PM

As for exposing a dim or dark scene closer to normal brightness and "printing down" in post for the final effect, that is not uncommon, it certain keeps the noise down and gives you snappier blacks.  

 

The downsides are if by exposing normally, you cause a bright object like a lampshade to clip and lose detail that would been retained if the shot had been exposed a little darker, and if dailies are left bright, the shot is edited in bright, and by the time you get to color-correction, no one wants to bring it down to the correctly dark level.

 

This is one reason why sometimes when you get to a scene that is supposed to look dim, rather than underexposing to darken the shot, you lower the ISO of the camera to darken it, thus seeing a darker image on the monitor and recording it that way but with less noise.  This is useful when working with a director who wants things to look darker on the monitor but you are worried about noise problems in post.

 

I usually do a mix of techniques, exposing a little darker but also lowering the ISO on the camera a little to darken further.  Or I just darken it halfway and hope I will be allowed to finish darkening it the rest of the way.


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#7 Tom Morrow

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Posted 21 January 2015 - 05:51 PM

Interesting distinction between exposure and ISO.  That prompted me to look up the definition of exposure, which is basically the amount of light falling on the sensor.  So technically, and as Jim used the word, changing the ISO does not change the exposure. 


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#8 Stuart Brereton

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Posted 21 January 2015 - 07:44 PM

I always try to expose the scene as I want it to look. I have been burnt too many times, by colorists who were either overzealous or under skilled, to trust anyone to carry out my instructions in my absence. Of course, even when you do expose the way you want it to look, it can be altered, but at least your intent was there for all to see.


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#9 David Mullen ASC

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Posted 21 January 2015 - 10:42 PM

Interesting distinction between exposure and ISO.  That prompted me to look up the definition of exposure, which is basically the amount of light falling on the sensor.  So technically, and as Jim used the word, changing the ISO does not change the exposure. 

Yes and no.  If changing the ISO changes the image brightness as output to the monitor, which in turn affects your exposure choice, then the ISO setting is causing a change in exposure.

 

Also, if you are using a camera where ISO settings are baked into the recording, then the ISO may not be changing what is hitting the sensor, but it is changing the signal in terms of image brightness.

 

We tend to think of exposure as whatever affects the range of luminance that gets recorded and therefore controls what we will have to work with in color-correction.  So only defining exposure as what hits the sensor is a bit limiting, or exact to the point of being impractical. All that matters is the image that we have to work with in post.

 

Put it this way, if the director wants me to darken the shot by another stop so that it looks dark enough on the monitor to suite him, but I am already working at a fairly high ISO rating because of the low light levels involved, and thus am worried about noise in post should any attempt be made to pull detail out of the shadows or push a color around, then I could just reduce the ISO rating by one stop and be giving the sensor the same amount of light while reducing the brightness of the displayed (and possibly recorded) image, whereas if I hadn't adjusted the ISO setting, I'd have to stop down one-stop and thus reduce the exposure plus the displayed image, so in effect, the ISO setting is affecting my exposure decisions.


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#10 Tom Morrow

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Posted 22 January 2015 - 01:55 AM

Thanks Jim for the nuanced discussion of what exposure means.

 

I don't want to beat a dead horse, but want to close the loop and note that it was your comment:

 

...rather than underexposing to darken the shot, you lower the ISO of the camera to darken it,

 

That led me to think you were saying that changing ISO didn't change the exposure.  If I understand correctly, that statement could be rewritten as

 

... rather than reducing light on the scene, stopping down the aperture, or reducing the shutter speed, you lower the ISO of the sensor to darken it.

 

Anyway the point is well taken that darkening by decreasing the ISO is, all things equal, better for noise reduction than darkening by reducing the light falling on the sensor. 


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#11 Gene Sung

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Posted 22 January 2015 - 10:51 AM

Thanks guys,

 

I'm using CineEI mode where the ISO is just fixed at the native 2000, so I just rated it at 800 and it seems to work pretty well in that I have a better idea of the final picture from the Log, keeps the maximum dynamic range of the camera and keeps the noise down.


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#12 Ravi Kiran

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Posted 22 January 2015 - 05:35 PM

You'd have to make sure not to have shadows or bright/clipped highlights in the frame that likely wouldn't be in such a dark scene, and might give away that the it was "over-lit" and darkened later.


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#13 Mark Kenfield

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Posted 27 January 2015 - 07:28 AM

My personal preference is always to test a camera thoroughly in terms of over and underexposure latitude before using it on a production. I like to have a really clear idea of what's going to happen to actors' faces at 1-stop, 2-stops, 3-stops and 4-stops both under and overexposure once the log image is graded back to normality with an s-curve applied to contrast.

 

You can then expose the camera confidently. Knowing, (depending on the camera) that 1-stop under will be a little dim, 2-stops under will be dark but with good detail, 3-stops under will be extremely dark with just a tiny amount of detail, and 4-stops under will be virtually black.

 

Knowing these limits for the camera you're using lets you keep noise under control (because you know your baseline), and allows you to expose for precisely the amount of detail you want to be seen in the final shot. It also lets you know how much you need to 'light the shadows' in order to maintain shadow detail.

 

As a general safety rule. I find that 2-stops under (on faces) is a happy medium for dark/low-key scenes. It gives you dark images with plenty of detail, and can easily be crushed down darker if you need.


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#14 David Baron

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Posted 29 January 2015 - 11:03 AM

Always be aware that many compressions really do a number to the shadows.  If you under expose on certain cameras that use a lower bit-rate you might get smearing in the shadows (not the case on the f7, but this almost killed me on a movi shot using a GH4). 

 

I would always rather have to pull down the shadows in post than risk loosing detail in the shadows of an under-exposed image.  Light the faces 1-2stops under anticipating the grade but no more than that.  This will help highlights or hard hits of lights from being over.


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