How?- properly bring down intentionally overexposure

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Seth Marshall

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How?- properly bring down intentionally overexposure

PostFri Aug 26, 2022 7:02 pm

Shooting LOG I often overexpose my image to intentionally lift my shadows to reduce noise. Sony cameras have their CineEI workflow for this. If I am intentionally 2 stops overexposed, what the proper way to bring down exposure before applying a LUT that is designed for footage to be properly exposed? If I'm supposed to use the "Offset" control what number represents one stop (the offset default is 25)? Does it matter if I'm in Log mode or not?

There used to be LUTs available with specific Offsets, but once the Sony Fs7 camera had a firmware upgrade so we had the ability to "bake in" those ISO exposure changes it appears those offsets went away.

I've seen before people often change the gamma setting but that throws everything off.
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Marc Wielage

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Re: How?- properly bring down intentionally overexposure

PostSat Aug 27, 2022 8:33 am

Seth Marshall wrote:Shooting LOG I often overexpose my image to intentionally lift my shadows to reduce noise.

I think this is a very bad idea for a lot of reasons. Noise is a function of lighting as well as exposure, so the danger you have in overexposure is sacrificing highlight detail -- clipping and destroying them -- for the same of less noise. You can do this in film negative (and in fact we often used to tell DPs to "give us a thick negative" by overexposing 1/3 or even 1/2 of a stop. But I think for digital images, you have to do the opposite and protect the highlights by underexposing a little bit, then compensate in the shadows with more fill light.

There are some great books out there on lighting and digital cinematography that go into this in great detail. I tell students, when in doubt, SHOOT TESTS. Find out the limits of your camera before the shoot, and figure out when noise is a problem and when highlight clipping (or shadow blockiness) becomes noticeable. And I don't think increasing ISO is the answer, either. There's a nominal range for every camera where the noise looks decent, and you just have to light to that stop, rather than opening wide up and increasing exposure in the camera. There are a lot of cameras out there that are rated at 1200 or even 1600, but the reality is you actually get better pictures at 800 (or lower). Tests will show you what the real usable range of the camera is.
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Uli Plank

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Re: How?- properly bring down intentionally overexposure

PostSat Aug 27, 2022 8:43 am

Marc, while I normally fully agree with you, this is a different issue.

Those Sony Slog cameras don't use the full dynamic range in most lighting situations. One or two stops of overexposure normally don't clip your highlights at all and get the shadows 'out of the mud'.

Of course one can ask why use log at all in such cases, when these cameras are offering some less radical profiles, like Cine1-4 or S-Cinetone.

There were LUTs specific for such overexposure all over the internet, but I haven't seen them lately. I tend to work by hand and eye…
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Re: How?- properly bring down intentionally overexposure

PostSat Aug 27, 2022 10:09 am

Marc, this is how Sony cameras work in Cine EI mode.
It let's you allocate more/less information above/below middle gray by offsetting your exposure, just like we used to do shooting on film and rating it at different exposure index.
Think of it as faux-RAW.
To bring back your exposure where it should live there are different strategies.
You can use the offset wheel, or you can use the contrast/pivot sliders.
What I find the most accurate, though, is to linearize your footage and back using 2 CST nodes, and create a node in between. Since in the middle node you are working in a linear space, a simple gain operation will correct your exposure.
Doubling the gain value will be a +1 stop correction, halving it will be a -1.
So, in the case of a +2 stop rating, the gain value should be 25.
Hope this helps.

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Re: How?- properly bring down intentionally overexposure

PostSat Aug 27, 2022 12:23 pm

Perhaps consider using CST instead of a LUT to bring the log footage into a proper color space for grading. Then you can use the grading tools to reduce the exposure, etc. Is that possible?

It is common practice with those cameras to over-expose by one or more stops as noted. If you don't, you will absolutely get noise in the darker regions of the image.
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Re: How?- properly bring down intentionally overexposure

PostSat Aug 27, 2022 1:45 pm

If it is pure log curve then offset is directly related to exposure but how Resolve units correspond to stops, don’t know. It depends on log curve parameters too, it is not universal. In ”turn de knobz” mode it doesn’t really matter what is what, just turn them until it looks good. In color managed workflow, exposure is easier to do properly if either tools are colorspace aware and you can do proper linear gain/exposure change or you can do linearization step in some node yourself and then apply gain. With gain it is easy, x stops change is multiplier formed by 2 raised to power of stops change, for example -2 stops will be 2^-2 which is 1/4=0.25
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Uli Plank

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Re: How?- properly bring down intentionally overexposure

PostSat Aug 27, 2022 2:59 pm

Unfortunately, Slog-2 is not really pure log and while Slog-3 is, IMHO, it's too wide even for 10 bit recording. So, we have a bit of a dilemma here. I'd not ever use Slog with 8 bit, BTW.

Just try on your own how far you can get with Slog-2 and 10 bit, using a CST.
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Seth Marshall

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Re: How?- properly bring down intentionally overexposure

PostSat Aug 27, 2022 10:19 pm

Thanks for the replies everyone. I believe offset is the way to go but it's been awhile since I've graded and thought I'd check in to see if this issue has been revisit.

I'm a DP and this is very common practice. Of course we consider our highlights before making these decisions. Most recently I intentionally overexposed 2 stops because space was dark and there was nothing at all above the top half of the waveform. The background was almost black and I wanted to make it as clean as possible. My delivery requirement was SLog3, so my decision was to rate at 200 instead of 800, the waveform filled in nicely and I have tons of detail and latitude for whatever they need to do in post.

Image looks great, I just want to make sure someone new at post doesn't decide to use gamma to correct for it!

EDIT: Actually I should mention the concern about someone unknowingly correcting exposure using gamma is exactly the reason I posted this. I saw a video somewhere awhile back where someone walked through all the various ways to correct exposure in lieu of having a LUT built intentionally for an exposure offset. I can't find that now but their use of color charts was a great way to see exactly what's going on.
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How?- properly bring down intentionally overexposure

PostSat Aug 27, 2022 11:39 pm

You should find and study the log curve of your camera, with native iso. log offer you the best dynamic range on native iso, choose the best for your shooting.
The problem of noise and compression of data in the shadow are only compression related, is often better to record less compressed and process later instead to have different quantity of noise in shadow middle and high lights.
Anyway the better way to reduce exposure is to add a node for exposure where use linear color space and change gamma value.

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Re: How?- properly bring down intentionally overexposure

PostSun Aug 28, 2022 1:14 am

Uli Plank wrote:Those Sony Slog cameras don't use the full dynamic range in most lighting situations. One or two stops of overexposure normally don't clip your highlights at all and get the shadows 'out of the mud'.

We've done many, many SLog projects (like with the F55 and the FX7 & FX9), and highlight clipping is always a problem. Usually the cheaper the camera -- particularly DSLRs and mirrorless still cameras that can shoot video -- the more problems we run into with dynamic range. Of course, the standard philosophy is "Expose to the Right," which generally I agree with, but to me the important thing is to avoid slicing off the specular highlights. We can't ever get them back, no matter what. There's a good middle ground where it's exposed just enough to avoid noise in the shadows, yet still not blow out the highlights.

Usually, we'd use a CST Node (to apply correct Input Color and Input Gamma to the Raw or Log file), followed by an Offset node, sometimes followed by a contrast curve, and then a couple of nodes that would trim the result and push it into the area we needed. But if the clip was intentionally overexposed, as the o.p. said, it could be disastrous in terms of clipping. Noise is not really that big an issue, as long as there's enough light on set and you're shooting at a reasonable ISO.

Of course, Noise Reduction is always an option. If I have time, I prefer to use Neat Video, but all these tools can be useful, and it's a question of using whatever's most appropriate for the time and budget available.

Uli Plank wrote:There were LUTs specific for such overexposure all over the internet, but I haven't seen them lately. I tend to work by hand and eye…

We have some tricks designed to soften clipped highlights, maybe add a little glow, defocus the highlights with a qualifier, that kind of thing, but it's never the same as real solid highlight detail. It's a bandaid fix at best. I'm guessing that's what the LUTs try to do, but bear in mind that a LUT can't store defocus or glow information.
Last edited by Marc Wielage on Mon Aug 29, 2022 1:50 am, edited 1 time in total.
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Re: How?- properly bring down intentionally overexposure

PostSun Aug 28, 2022 7:03 am

Marc Wielage wrote:
Uli Plank wrote:There were LUTs specific for such overexposure all over the internet, but I haven't seen them lately. I tend to work by hand and eye…

We have some tricks designed to soften clipped highlights, maybe add a little glow, defocus the highlights with a qualifier, that kind of thing, but it's never the same as real solid highlight detail. It's a bandaid fix at best. I'm guessing that's what the LUTs try to do, but bear in mind that a LUT can't store defocus or glow information.

If they are technical exposure compensation luts they probably do just pure exposure change, one or two stops down etc, meant for specific log curve flavor.
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Re: How?- properly bring down intentionally overexposure

PostSun Aug 28, 2022 11:44 pm

S-Log2 IS very much a Log profile and is actually one of the best Log encoding profiles you can use as it has the most efficient use of bits compared to S-Log, S-Log3 and other Cineon derivatives. S-Log2 offers approximately 14 stops of dynamic range on practical implementations.

S-Log3 has far less usable bits and is actually capped at the knees at ~14 stops DR across most cameras so you will never truly take advantage of the additional DR available on that profile. I don't know why people hype it up.

Trust the cold hard facts, not the hype or hearsay.

Both S-Log2 & S-Log3 offer a little over 6 stops DR above mid-gray so there is plenty of highlight range. If you are over-exposing by 2 stops, that reduces the highlight range to 4 stops above mid-gray. Still more than plenty for most scenarios, especially if you're delivering to SDR.

If you are trying to preserve specular highlights, that's a different discussion, but even then, remember that SDR peaks at approximately 2.5 stops above mid-gray. You would still need to perform some mapping to bring those specular levels down to an SDR range regardless of whether those highlights clip at 4 stops or 6 stops.

Instead of using a LUT, you'd be better served using Color Management. Normalize your S-Log2/3 to a timeline space like Rec.2020 Intermediate (without input/output tone mapping) and then use the exposure controls to bring your highlights down by 2 stops (if you've over-exposed by 2 stops). This is a much better and accurate workflow than using a LUT.
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Re: How?- properly bring down intentionally overexposure

PostMon Aug 29, 2022 1:56 am

Hendrik Proosa wrote:If they are technical exposure compensation luts they probably do just pure exposure change, one or two stops down etc, meant for specific log curve flavor.

You can't get it back if it's really clipped. Not ever. Not even in film. "Exposure compensation" doesn't mean anything. Darkening? Pulling down contrast? C'mon. If the highlights are blown-out, it's gone forever.

The one possible exception is the Blackmagic cameras' "Highlight Recovery" mode, and it can coax a little less clipping out of the signal. But... it only goes so far, and it doesn't work on anything else.

Many, many times, I've run into (say) Red camera clips where the background windows were radioactive/overexposed, and no amount of dropping the ISO or Exposure controls could get that information back. We could improve it to the point where it wasn't a flat line on the waveform, but it never looked good. Basically, it's hard to overcome bad work by the DP, when they didn't use an ND gel on the windows and/or didn't fill the actors in the foreground properly. Usually if I tactfully point that out, the DP will sigh and admit, "yeah, I wish we'd had time to fix that on set. But you've at least made it look a little better."

RikshaDriver wrote:Instead of using a LUT, you'd be better served using Color Management. Normalize your S-Log2/3 to a timeline space like Rec.2020 Intermediate (without input/output tone mapping) and then use the exposure controls to bring your highlights down by 2 stops (if you've over-exposed by 2 stops). This is a much better and accurate workflow than using a LUT.

I'm a big fan of color management and use it all the time. But again: you can't get the highlight information back if it's blown out -- not with a LUT, not with Color Management, not anything. Once the camera sensor itself is overloaded... it's gone.

The new Alexa S35 camera has some specific tweaks where they've actually managed to extend dynamic range to a whopping 17 stops, but they kind of cheated by lowering the black sensitivity and improving shadow detail. I've done quite a few Alexa projects and they're often a pleasure to work on.

https://www.arri.com/en/company/press/p ... -35-camera

Even if the DP does let the Alexa highlights clip a little bit, often it does so in a pleasing way that's kind of reminiscent of film, which I think was Arri's deliberate intent. But I don't see the same results with a cheap Sony camera shooting SLog, especially with a compressed codec like H.264. Those are a nightmare to deal with.
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Re: How?- properly bring down intentionally overexposure

PostMon Aug 29, 2022 6:21 am

Marc Wielage wrote:
Hendrik Proosa wrote:If they are technical exposure compensation luts they probably do just pure exposure change, one or two stops down etc, meant for specific log curve flavor.

You can't get it back if it's really clipped. Not ever. Not even in film. "Exposure compensation" doesn't mean anything. Darkening? Pulling down contrast? C'mon. If the highlights are blown-out, it's gone forever.

Why do you keep insisting that they are really clipped? OP already said highlights are protected. Why not just read what is written instead of coming up with bazillion theories about things no-one said nothing about. Are you arguing that downstepping two stops is impossible? 17 stops in new Alexa is absolutely useless if you keep the lens cap on! In my career I have never seen anyone recover data from behind lens cap so why even bring the Alexa up? To be really crystal clear here, second half was rhetorical, no need to waste paragraphs for explaining how dop and ac should actually make sure there is no cap on so they can clip all highlights.
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Re: How?- properly bring down intentionally overexposure

PostMon Aug 29, 2022 9:40 am

Hendrik Proosa wrote:Why do you keep insisting that they are really clipped? OP already said highlights are protected.

I just re-read the original message twice, and there's nothing there about protecting the highlights. I'm merely saying that the subject of the message -- How to properly bring down intentionally overexposure [sic] -- is crazy. If you're not clipping the image, then it's a normal exposure -- not an overexposure. I think we have a difference in terminology.

I started out as a camera operator for 5-6 years, so I'm painfully aware of what overexposure is, what correct exposure is, and what underexposure is. If it's overexposed, it's gonna be clipped; if it's exposed well, according to the book, then highlights won't be clipped and there's no problem. Don't intentional overexpose anything -- just expose it correctly, and bear in mind key-to-fill ratio. If you don't understand that, do a Google search. And when in doubt... shoot tests.
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Re: How?- properly bring down intentionally overexposure

PostMon Aug 29, 2022 12:14 pm

Relax, guys.
It's just a big misunderstanding. While the OP is obviously referring to ETTR (expose to the right), Marc is getting this as clipping.

But even with ETTR you may need to clip some small highlights, depending on scene contrast. So, Marc's tricks for making those look more acceptable are still very valuable.
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Re: How?- properly bring down intentionally overexposure

PostMon Aug 29, 2022 12:35 pm

Seth Marshall wrote:Shooting LOG I often overexpose my image to intentionally lift my shadows to reduce noise. Sony cameras have their CineEI workflow for this. If I am intentionally 2 stops overexposed, what the proper way to bring down exposure before applying a LUT that is designed for footage to be properly exposed? If I'm supposed to use the "Offset" control what number represents one stop (the offset default is 25)? Does it matter if I'm in Log mode or not?

There used to be LUTs available with specific Offsets, but once the Sony Fs7 camera had a firmware upgrade so we had the ability to "bake in" those ISO exposure changes it appears those offsets went away.

I've seen before people often change the gamma setting but that throws everything off.
To answer the original question. Assuming you protect highlights from clipping AND overexpose by boosting your lights or opening the aperture. If you're just increasing the ISO there will be 0 benefit with this workflow

If you wanna be mathematically correct with exposure you could use the HDR global wheel (set the gamma tag to whatever the footage is in) or go into linear with a CST and use the Gain (0.5 is -1 stop. 0.25 is -2 stops etc) as some people already pointed out.

Using the HDR global wheel is probably the most convenient way to do this, because you could also tag the entire timeline correctly and the leave the tool itself at "use timeline".

Offset in a pure Log like ACEScc does the same thing, but there are no easy to use values with the offset tool. Each Log curve would need different values of offset.
Last edited by Sven H on Mon Aug 29, 2022 2:34 pm, edited 1 time in total.
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Re: How?- properly bring down intentionally overexposure

PostMon Aug 29, 2022 1:54 pm

Marc Wielage wrote:If you're not clipping the image, then it's a normal exposure -- not an overexposure. I think we have a difference in terminology.
Thinking of the False Color feature in the Pocket, I would normally exposing the scene to get my 18% Gray Card in the green.

If I then open the Iris by two stops (assume highlights are not clipped after doing so), I believe this is what is meant by "over" exposed in this context.

Maybe it's technically not, because nothing clips, but I believe that's what's meant here.
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Re: How?- properly bring down intentionally overexposure

PostMon Aug 29, 2022 2:56 pm

Jim Simon wrote:
Marc Wielage wrote:If you're not clipping the image, then it's a normal exposure -- not an overexposure. I think we have a difference in terminology.
Thinking of the False Color feature in the Pocket, I would normally exposing the scene to get my 18% Gray Card in the green.

If I then open the Iris by two stops (assume highlights are not clipped after doing so), I believe this is what is meant by "over" exposed in this context.

Maybe it's technically not, because nothing clips, but I believe that's what's meant here.


I was going to make a similar point - I've been wondering what is actually meant by overexpose by two stops? Terminology is potentially confusing here.

As a stills photographer I would normally spot meter a gray card in the same light as the main subject and take that as my basic exposure. Opening up two stops on that reading would then be two stops overexposure (basically same thing as Jim is saying). It might or might not clip depending on the scene.

Since getting into shooting video I have taken to exposing using the waveform or parade scopes on an external monitor (Ninja V or Video Assist12G with ProRes Raw/BRAW raw video from Nikon Z6). By trial and error I have found I am getting best results by exposing to the right but ensuring that the brightest highlights are not clipping (indicated by the flat line on the waveform scope). However, if I open up two stops on that I am definitely clipping and there is no recovery of detail in those highlights. If they're gone, they're gone.

Both scenarios are technically overexposure. One might or might not be ok in the highlights, the other is definitely not ok.
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Re: How?- properly bring down intentionally overexposure

PostTue Aug 30, 2022 7:14 am

mickspixels wrote:Since getting into shooting video I have taken to exposing using the waveform or parade scopes on an external monitor (Ninja V or Video Assist12G with ProRes Raw/BRAW raw video from Nikon Z6). By trial and error I have found I am getting best results by exposing to the right but ensuring that the brightest highlights are not clipping (indicated by the flat line on the waveform scope). However, if I open up two stops on that I am definitely clipping and there is no recovery of detail in those highlights. If they're gone, they're gone.

That is exactly right -- well-said.

Uli Plank wrote:Relax, guys. It's just a big misunderstanding. While the OP is obviously referring to ETTR (expose to the right), Marc is getting this as clipping. But even with ETTR you may need to clip some small highlights, depending on scene contrast. So, Marc's tricks for making those look more acceptable are still very valuable.

I think there's a happy medium where you expose to the right but NOT lose any highlights. If you're careful, it can be done. A huge part of it is just shooting the scene well and giving it sufficient fill light on set. I have infinite respect for DPs who can make the right judgements on knowing how much fill to provide on set, knowing they can always bring that down in post and add contrast while retaining highlight detail.

The picture below is a good example:

Image

The left side shows blown-out windows where they've exposed for the walls. The picture on the right has more fill (or possibly some digital fixes) and non-clipped windows. One reason why I recoil at clipped highlights is that this doesn't happen in film (if you know what you're doing), and to me it just makes a digital image more "harsh and edgy" (to coin a phrase). The more we can mimic the pleasing response of motion picture film, the better off we are and the more natural the image looks.
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Re: How?- properly bring down intentionally overexposure

PostTue Aug 30, 2022 8:01 am

I'd never let a window blow out with a modern camera.

But one usually needs to let a a direct light source in the frame or small reflections on chrome or glass clip, or the rest of the frame would get too dark. That's what early versions of automatic exposure in BM's cameras did wrong.

I know, other than on film, such highlights would look ugly in electronic cameras. That's where Marc's tricks would be needed to make them look more natural. The recently added 'Halation' filter in DR will be helpful too. Don't forget to give back some color to such highlights if the light in your scene is not pure white.
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Re: How?- properly bring down intentionally overexposure

PostWed Aug 31, 2022 1:03 am

Uli Plank wrote:I'd never let a window blow out with a modern camera.

I wish our clients would follow your example! Generally, what happens with us is this...

Image

That's what I think of when I hear "intentional overexposure."
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Re: How?- properly bring down intentionally overexposure

PostWed Aug 31, 2022 3:37 pm

Uli Plank wrote:That's what early versions of automatic exposure in BM's cameras did wrong.
The original Pocket did that. I actually prefer it.

If you got Zebras, then the sensor was clipping. Changing ISO had no effect on them.

The Pocket 4K changed that, making the Zebras...less reliable, I think.
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Re: How?- properly bring down intentionally overexposure

PostWed Aug 31, 2022 4:08 pm

I'm going to grumble about two points:

1) ETTR, common and accepted as it is, seems to ignore the degradation which occurs when you bring highlights nearer to clipping (without clipping). Depends on the camera obviously, but is crucial information (as opposed to specular highlights) exposed at 90 or 95% such a great idea?

2) you can't count the number of 35mm movies with 100% blown-out skies..... And lower budget feature films where there wasn't the time or resources to balance the interior, so everything outside is clipping in a pretty ugly way, film notwithstanding.

Film or digital, blown-out windows could be deemed a style. Or blown-out windows and dark interiors:

vlcsnap-7010-05-14-05h13m52s526.jpg
vlcsnap-7010-05-14-05h13m52s526.jpg (446.18 KiB) Viewed 3916 times
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Re: How?- properly bring down intentionally overexposure

PostWed Aug 31, 2022 5:22 pm

John Paines wrote:I'm going to grumble about two points:

1) ETTR, common and accepted as it is, seems to ignore the degradation which occurs when you bring highlights nearer to clipping (without clipping). Depends on the camera obviously, but is crucial information (as opposed to specular highlights) exposed at 90 or 95% such a great idea?



Common sense is required. According to Jeff Schewe (digital photography pioneer and author), the idea of Expose to the Right was originally proposed by Thomas Knoll (Mr Photoshop) where he suggested that a better signal to noise ratio (SNR) could be achieved by moving the exposure to the right of the metered exposure on an image histogram as long as the scene contrast was within the dynamic range of the sensor. Nobody ever suggested sacrificing the quality of the image in doing so.

So definitely going over the top with ETTR is not recommended. A nice balance between minimising shadow noise and retaining good detail in the highlights is the idea. In my experience, erring on the side of caution where highlight details are concerned is very sensible - as above, when they're gone, they're gone.
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Re: How?- properly bring down intentionally overexposure

PostWed Aug 31, 2022 5:51 pm

Proponents of ETTR insist that "common sense" means routinely overexposing images. That's why it's become a general principle -- at least in online discussion forums.

Whether the benefits are worth the risks hasn't, to the best of my knowledge, ever been demonstrated. And at what capture standards? Those which were common when ETTR was first proposed, or 10/12 bit 4:2:2 or better on the latest sensors with 12+ stops of DR?

I wonder also if the practice is consistent with long-standing aesthetic standards, which don't emphasize preserving shadow detail in graded material, but that's for another day.
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Re: How?- properly bring down intentionally overexposure

PostThu Sep 01, 2022 12:11 am

Like many other concepts and phrases there is a certain usefulness in the idea behind ETTR, but if applied by itself oft leads to a mess.

One really, really needs to always be aware of the entire desired capture. Shadows through highlights.

I've been asked how to fix images where they exposed to retain highlights out a window. And relied on the DR of their marvelous log capture device to "hold" all interior data.

Which, technically, was captured.

However ... the hoped-for midtones of skin in the expected final image were only a third stop higher than things expected be mid-shadows.

Hence banding would result if you really lifted the mids to their "proper" visual brightness.

Had they really studied that histogram in-cam, and thought ... they'd have added lights for those midtones or gelled the windows.

Something *useful*.

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Re: How?- properly bring down intentionally overexposure

PostSat Apr 01, 2023 2:03 pm

RikshaDriver wrote:S-Log2 IS very much a Log profile and is actually one of the best Log encoding profiles you can use as it has the most efficient use of bits compared to S-Log, S-Log3 and other Cineon derivatives. S-Log2 offers approximately 14 stops of dynamic range on practical implementations.

S-Log3 has far less usable bits and is actually capped at the knees at ~14 stops DR across most cameras so you will never truly take advantage of the additional DR available on that profile. I don't know why people hype it up.

Trust the cold hard facts, not the hype or hearsay.

Both S-Log2 & S-Log3 offer a little over 6 stops DR above mid-gray so there is plenty of highlight range. If you are over-exposing by 2 stops, that reduces the highlight range to 4 stops above mid-gray. Still more than plenty for most scenarios, especially if you're delivering to SDR.

If you are trying to preserve specular highlights, that's a different discussion, but even then, remember that SDR peaks at approximately 2.5 stops above mid-gray. You would still need to perform some mapping to bring those specular levels down to an SDR range regardless of whether those highlights clip at 4 stops or 6 stops.

Instead of using a LUT, you'd be better served using Color Management. Normalize your S-Log2/3 to a timeline space like Rec.2020 Intermediate (without input/output tone mapping) and then use the exposure controls to bring your highlights down by 2 stops (if you've over-exposed by 2 stops). This is a much better and accurate workflow than using a LUT.


i worked with slog2 for some years and absolutely had to ettr+2 for slog2 because middle gray sits pretty low with this one. if you do wysiwyg exposure you will end up with lots of really nasty noise within your shadows, and even mids, compressing skin detail and color information, so separation gets bad and the "raised" face looks pretty flat. Sony Sensors i know are pretty noisy in dark areas from a7s to blackmagic.

also slog2 is way harder to grade manually than slog3 in my experience. Thats why most dslr shooters prefer slog3. its pretty straigt forward with lgg corrections. slog2 has shifted colors and doesnt respond very well to standard lgg.

back in the days i had some nice -2 and -3 compensation luts for slog2, provided by sony. Unfortunately the 8bit codec of my a7s2 couldnt stand it and the color shifts applied by it broke the image apart.

tbh this behavior of slog and sony sensors tought me, that they are not really those "low light monsters" everyone talks about, because the moment you have low light levels you absolutely have to raise the iso and overexpose alot to get your image out of the heavy noise floor. And usually you absolutely crush all highlights in the scene at the same time.

This became even clearer to me, when i switched to my ursa mini g2, which kinda works completely the other way around.

now i only use ettr if the DR/contrast of the scene is pretty low, so even by pushing (with aperture, or 2nd base iso if available) the exposure by 2-3 stops nothing will clip. This may give you better separation because it pushes the signal to the linear part of the log curve.
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Re: How?- properly bring down intentionally overexposure

PostSat Apr 01, 2023 10:03 pm

One of the original arguments for ETTR that dis make sense, is by doing that you had more bits available for recording deep deep grays going to black and avoiding banding. This is still valid, but is far less relevant with 10 bit and greater sensors.

Highlight clipping is unrecoverable, and is one of the most ugly visual effects. Better banding in the dark regions than blown highlights.
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Re: How?- properly bring down intentionally overexposure

PostSun Apr 02, 2023 1:58 am

I just re-read this entire thread, and one thing nobody stresses enough is...

THE IMPORTANCE OF KEY-TO-FILL RATIO.

Exposure is one thing, but if you don't fill everything in the dark part of the shot, we can't dig it back out. Expose for the highlights so they're not clipped and blown out, and if the other parts of the room are too dark... use fill lights! This is far more critical than "intentional overexposure."

An article for reference;

What Are Contrast Ratios and How Do You Use Them?
https://www.premiumbeat.com/blog/how-us ... ilmmaking/

We can always try to force more light into the dark areas during final color, but if we're trying to bring up a muddy, underexposed image without enough fill, it's never going to look good. That's with film, high-end digital cameras, cheap digital cameras, anything. Doesn't matter if it's SLog, VLog, or any Log. Lighting is really critical, and you can't necessarily make up for terrible lighting in final color.

A saying I've been using for more than 30 years: we can always make it better, but we can't always make it good.
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Re: How?- properly bring down intentionally overexposure

PostMon Apr 03, 2023 1:53 am

Agree totally with Marc. Fixing the lighting on location is always best. All post processing efforts will never beat good lighting initially.
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Re: How?- properly bring down intentionally overexposure

PostMon Apr 03, 2023 3:56 am

Without going into the details if that is a good strategy or not, with the new HDR tools, the "best" way to change exposure is to setup the correct color space in teh HDR tools (I think your is something like Slog/Slog2) and simply ask for -2 global exposure.
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Re: How?- properly bring down intentionally overexposure

PostMon Apr 03, 2023 10:09 pm

waltervolpatto wrote:Without going into the details if that is a good strategy or not, with the new HDR tools, the "best" way to change exposure is to setup the correct color space in teh HDR tools (I think your is something like Slog/Slog2) and simply ask for -2 global exposure.


Thanks for this. I was going to mention that a linear/gain node doesn't work correctly (for exposure) unless the timeline is the same as the camera gamma/gamut. A stop in Davinci WDR or 709 is different than a stop in S-Log, HDR tab for the win.

Good Luck
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Re: How?- properly bring down intentionally overexposure

PostTue Apr 04, 2023 1:10 am

Wow, its amazing how a very common and correct exposure policy for Slog has turned out to be so controversial and elicited so many responses. So here's one more from a DP who's shot tons of Slog:

1- First - Seth. Yes you were on the right track to use "offset" before your LUT (before is critical) if you are not using an exposure compensated LUT. That's what i used to do . However I just learned from Howard roll (see the posts above and below ) that a better tool might be the "global " wheel in the HDR palette, which can give an adjustment that is more akin to what your camera would do. I haven't experimented with it yet but it looks powerful.

Don't worry about how many stops you are adjusting, Just bring the picture down to where you want it . Chances are you'd have to adjust exposure somewhat even if you weren't using log . You can also use a CST or color management and then just lower the exposure in the same way. In either case "Offset" or maybe better "HDR Global" is what you want otherwise you are altering the nature of your curve. That's fine if you want to but its a choice better made after the basic exposure is set.

2 - Regarding the word "overexposure" . A simple nomenclature confusion might be at the heart of a lot of this. Technically "overexposure" is the wrong term though many of us use it because its simple. Actually the "so called correct" ISO rating for any film stock or camera is just what the manufacturer has chosen to label their product but its to some extent arbitrary. Typically DP's have very often rated the ISO of both film negative and Slog lower than the manufacturers rating and typically to get "more exposure" for better blacks at the expense of some highlight latitude. I might say I'm "overexposing", but I'm not , I'm correctly exposing for how I know the sensor or film stock will respond to the scene . Likewise if I "push" a negative in development I'm not "underexposing" in camera, I'm rating the negative for a push process. That's why Sony uses the term EI ( exposure Index) instead of ISO.
Its tricky shooting with an A7 series camera because they don't have Cine EI and can't compensate in the viewfinder for rating the camera slower, so in fact your image will look overexposed on the EVF, but it won't actually be in Post.
If you have a scene with a lot of dynamic range ( often uncontrolled and and outdoors), then you may very well choose the manufactures ISO because you want to preserve highlights, not shadows.

3- It sounds like Marc has had to deal with a lot of badly shot video that actually was overexposed which is just shoddy workmanship , or it was shot in uncontrolled situations where the DP had to pick his/her poison - i.e.. to choose whether to sacrifice the shadows or the highlights. That's just a judgement call.

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Last edited by Leonardo Levy on Tue Apr 04, 2023 8:00 am, edited 3 times in total.
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Re: How?- properly bring down intentionally overexposure

PostTue Apr 04, 2023 2:37 am

Leonardo Levy wrote:Its tricky shooting with an A7 series camera because they don't have Cine EI and can't compensate in the viewfinder for rating the camera slower, so in fact your image will look overexposed on the EVF, but it won't actually be in Post.

All very good points here, an excellent overview!

Just one remark: some of the recent Sony Alpha series models offer "Gamma Display Assist" now under the Display Options now plus below that "Assist Type" with choices for Slog2 and 3 plus HLG.
It does not compensate for different exposure ratings, but it's a good start ;-)
Maybe AI can help you. Or make you obsolete.

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Re: How?- properly bring down intentionally overexposure

PostTue Apr 04, 2023 4:12 am

Leonardo Levy wrote:1- First - Seth.Yes You are correct use "offset" before your LUT


You're of course free to grade footage however you like but offset is basically grabbing the whole image and sliding it up or down the scale. Using exposure in the HDR tab, or a linear node is identical to using exposure in the Raw tab. Here you can see the Raw tab and the HDR tab yield identical results while the offset node has crushed the blacks and lost detail.

Good Luck

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Leonardo Levy

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Re: How?- properly bring down intentionally overexposure

PostTue Apr 04, 2023 7:22 am

Thanks, I confess I overlooked those responses and was not very familiar with the HDR tab .
I just found this tutorial


and he starts off showing the advantage of using the global wheel instead of offset for exposure adjustments. Makes sense to me and I will try that in the future.

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Re: How?- properly bring down intentionally overexposure

PostTue Apr 04, 2023 8:10 am

Howard Roll wrote:You're of course free to grade footage however you like but offset is basically grabbing the whole image and sliding it up or down the scale. Using exposure in the HDR tab, or a linear node is identical to using exposure in the Raw tab. Here you can see the Raw tab and the HDR tab yield identical results while the offset node has crushed the blacks and lost detail.

Some years ago, Patrick Inhofer of MixingLight.com did a good tutorial series that basically asked, "is it better to try to adjust exposure in the RAW tab, or with the usual Lift/Gamma/Gain controls?" And he came to the conclusion that ultimately, there's not a huge amount of difference. But it's a lot faster to use LGG simply because we can get to the knobs on a control surface faster.

I do use Offset frequently, and it's an open question as to the differences between Offset on the Primary tab or on the HDR tab. They ARE different, but (to me) the differences are subtle. If Walter says they're better on the HDR tab, I'll believe him.
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Re: How?- properly bring down intentionally overexposure

PostTue Apr 04, 2023 9:17 am

Offset in a pure log environment is the exact same as gain in linear (aka exposure).

the main difference between Offset and HDR Global comes down to one thing (only talking exposure for now).
usually we are not in a pure log environment but in a semi-log. all those curves (except ACEScc and S-Log/S-Log2) have a linear extension in the shadows.

That's why you're lifting or crushing the shadows if you're using Offset.

Don't ask about white balance. that's a way more complex topic ;)
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Re: How?- properly bring down intentionally overexposure

PostTue Apr 04, 2023 9:25 am

If you offset below zero, and clamp it, it is gone. Scaling values down don't push them below clamping level even if you scale them with zero. This is the difference. But when not clamping, offset in pure log is mathematically equal to scaling on linear values.
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Re: How?- properly bring down intentionally overexposure

PostTue Apr 04, 2023 2:27 pm

Marc Wielage wrote:
I do use Offset frequently, and it's an open question as to the differences between Offset on the Primary tab or on the HDR tab. They ARE different, but (to me) the differences are subtle. If Walter says they're better on the HDR tab, I'll believe him.


Marc, you know I use offsets like there is no other control, the question was "the best strategy" to recover those two stops of exposure and mathematically teh HDR tools do what the RAW tab will do.

do I use it? Yes, if I have a scene that is all underexposed by (let's say) a full stop, I grab all teh shot, +1 in HDR exposure tool, ripple to the group and I'm good to go.

If i can do a correction to the whole group in one swoop, I will do it.
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Re: How?- properly bring down intentionally overexposure

PostTue Apr 04, 2023 4:37 pm

Hendrik Proosa wrote:If you offset below zero, and clamp it, it is gone. Scaling values down don't push them below clamping level even if you scale them with zero. This is the difference. But when not clamping, offset in pure log is mathematically equal to scaling on linear values.
Almost correct. Exposure scales in linear, where negative (below zero) values are possible due to sensor noise or other operators before the exposure adjustment.

Clamping is destructive anyway, doesn't matter if you use offset or hdr global. since we're talking resolve wich is 32 bit float, there is no clamping by default.
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Re: How?- properly bring down intentionally overexposure

PostThu Apr 06, 2023 2:06 pm

Sven H wrote:
Clamping is destructive anyway, doesn't matter if you use offset or hdr global. since we're talking resolve wich is 32 bit float, there is no clamping by default.


in all this discussion, we are "assuming" that something is left in the RAW, if you saturate the sensor (clipping) there is nothing left anyway to restore...
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