Jump to content
maxotics

Are S-LOGS More Destructive Than They're Worth?

Recommended Posts

24 minutes ago, Deadcode said:

i have a question which is just partly related to the original topic.

If i record ML raw with my 5D2, am i able to create proper HDR footage out of it? i know it's limited to 11.7 stop DR and HDR requires 15 EV, but HDR is just a tonemapping right?

It's related!  You can't change the physics of a sensor.  100 ISO essentially means, the sensor can get a perfectly accurate color, with no noise, at f1 for 1 second, or something like that.  The more you move away from that strength of light, the less the sensor can read it, to the point where it is "guessing" so badly it looks like noise.  Let's just talk about light at the 7th stop of DR in a physical scene of 15 stops and the main exposure would be to capture the 3rd to 9th stop of the scene (that is, would expose for 6th stop of physical brightness).  In 8bit photo/video, the 10th stop of physical light becomes white because it's the 6th stop, end of the 8-bit space.

How to get that data?  In HDR, the camera takes a different exposure where it exposes for the 7th stop of physical brightness, meaning the 6th stop of 8bit recording is getting that extra stop in the scene.  If you shoot RAW, however, you're getting that 7th stop because you're getting 12 stops of dynamic range.  HOWEVER, the raw values at the 7th stop aren't as good as the main exposure; again, the further away you move from your main exposure the less quality color.  So which is better, using the 7th Stop of RAW OR using a 7th stop where the amount of light into the camera has been changed.  

I haven't seen any analysis of that question but it is a super one in my book!  Although ML has an HDR video feature, I don't believe it take different exposures, it just take a different reading of the RAW data.  If the manufacturers could figure out how to change aperture or shutter-speed 30 times a second, for video, well, that would be interesting indeed! 

Share this post


Link to post
Share on other sites
EOSHD Pro Color for Sony cameras EOSHD Pro LOG for Sony CamerasEOSHD C-LOG and Film Profiles for All Canon DSLRs
2 hours ago, maxotics said:

 

I haven't seen any analysis of that question but it is a super one in my book!  Although ML has an HDR video feature, I don't believe it take different exposures, it just take a different reading of the RAW data.  If the manufacturers could figure out how to change aperture or shutter-speed 30 times a second, for video, well, that would be interesting indeed! 

at HDR raw video the camera sets different ISO for half of the resolution. For example ISO100/ISO800 will increase the dynamic range about 2.5 stops. the overlapped region is full resolution the highlights and the deep shadows are half resolution with some aliasing. works perfectly for stills, but in video the resolution is a little bit low and the post-process takes ages (it creates 20 bit raw)

 

Share this post


Link to post
Share on other sites

Between the two of us we're going to confuse a lot of people about HDR :)  In reference to the issues with S-LOG, I want to point out that the concept of ISO is that, again, it's just a reference point of where an image should be properly exposed in the data stream.  As far as I know, ISO has no functional effect on the sensor's work.  It is only AFTER the sensor is exposed that it is used to set the gain, so to speak, on the signal.  And this is where it isn't as simple as extending the ISO, like in HDR, to increase dynamic range because there is a component of perception in dynamic range, which is why HDR can easily look artificial or plastic.   When you set ISO, you're also setting your center point of exposure.  Brightness and dimness extend out from it in a way that should be natural to us.  When you have two frames of data, one at ISO 100 say, and one at ISO 800, you actually have two perceptual expectations of how light goes from dark to bright.  When you try to fill in clipped areas in either direction, dark or bright, our brain can quickly see when something doesn't make sense.  This relates to S-LOG because it too records a range of light beyond our normal expectations.  Mostly, we don't notice if there is little color because we're more sensitive to basic contrast.  In both HDR and S-LOG, the more color fidelity you go after, in normal DR, the more these issues fight back.

Share this post


Link to post
Share on other sites
On 07/07/2017 at 4:46 PM, maxotics said:

Oliver, you know I love you to death and greatly admire your work.  But I have to push back a bit here.  When you say "S-LOG is totally worth it, if you now now to use and treat it." You're insinuating that SLOG is better than standard profiles, that everyone should shoot it?  Right?  It is ONLY extended dynamic range in the fact that it picks up extended brightness values in the scene, it is NOT extended COLOR range, in fact, quite the opposite.  The extended brightness range you get are TRADED OFF for color fidelity.  Now, you may only want to see those 10 million colors, and I respect that, but to say that everyone should shoot in a way that degrades the camera FULL color fidelity I don't understand.  

As for highlight rolloff, yes, I can see that, but again, it ignores what you lose in the mid-tones.

Please think about what I wrote more carefully and tell me why S-LOG does not trade off "brightness contrast" in a scene for color fidelity in the full gamut we expect.  Tell me why what you're saying is an objective statement that SLOG is better than standard profiles.

Thanks for the love. 

Im not saying everyone should shoot S-LOG.

My opinion is that S-LOG, under a skilled hand, will more than likely give more pleasing results - with the majority of users on here are going for the "filmic, organic" look. 

Forgive me, I'm not that interested in the scientific depth of how it works. I just learn to expose it and grade it like a painter would choose their paints. 

You're right though, you do lose colour information. Put any A7 camera on PP off and bang! Colour explosion. BUT... the dynamic range is very poor. 

I feel what you lose in colour, is worth the benefit for that LOG range. It's not enough of a loss in my eyes to dismiss S-LOG.

Share this post


Link to post
Share on other sites
44 minutes ago, Oliver Daniel said:

Thanks for the love. 

Im not saying everyone should shoot S-LOG.

My opinion is that S-LOG, under a skilled hand, will more than likely give more pleasing results - with the majority of users on here are going for the "filmic, organic" look. 

Forgive me, I'm not that interested in the scientific depth of how it works. I just learn to expose it and grade it like a painter would choose their paints. 

You're right though, you do lose colour information. Put any A7 camera on PP off and bang! Colour explosion. BUT... the dynamic range is very poor. 

I feel what you lose in colour, is worth the benefit for that LOG range. It's not enough of a loss in my eyes to dismiss S-LOG.

On paper 8bit Slog is total garbage. In real world situation it's very handy. Andrew created a very nice A7s Slog2 vs 5D3 MLRaw video long time ago and the result were quite pleasing. He was blown away by the results too. 

Share this post


Link to post
Share on other sites
2 hours ago, Oliver Daniel said:

Forgive me, I'm not that interested in the scientific depth of how it works. I just learn to expose it and grade it like a painter would choose their paints. 

If someone set up a studio and paid professionals to light it all within 6 stops (like a real TV set) and asked you to bid for the camera work and you said you shoot everything in S-LOG what should they conclude?  What if they say, "Oliver, the way I understand it, an 8-bit camera's normal gamut captures 16 million colors in 6 stops of dynamic range with the noise expected within those 6 stops.  If you shoot LOG, you're bringing in values above those 6 stops, which don't actually exist on our stage, which will be noisy.  Why would you trade any of those 16 million colors on our stage, for colors (brightness) that is not on our stage?"  You're using "science" as a reason not to really think about this stuff.  Again, maybe I'm wrong, but I haven't heard any argument against what I see.  

Another way of looking at it is that when you say you shoot everything LOG it's like a photographer saying they shoot everything 1600 ISO and when you challenge them on it they say they really know how to "use it and apply noise reduction expertly."  Would you want photographs from such a photographer?  Of course not (unless they're shooting a scene where deep shadows are more important than the general exposure).    When you shoot S-LOG you are also shooting high ISO in a way.  Why would you ever want to do that in a scene lit to perfectly fit the gamut of people's displays?

If you want to see for yourself, light a scene within 6 stops and shoot both in a normal profile S-LOG and see for yourself.  

Share this post


Link to post
Share on other sites
11 hours ago, maxotics said:

If someone set up a studio and paid professionals to light it all within 6 stops (like a real TV set) and asked you to bid for the camera work and you said you shoot everything in S-LOG what should they conclude?  What if they say, "Oliver, the way I understand it, an 8-bit camera's normal gamut captures 16 million colors in 6 stops of dynamic range with the noise expected within those 6 stops.  If you shoot LOG, you're bringing in values above those 6 stops, which don't actually exist on our stage, which will be noisy.  Why would you trade any of those 16 million colors on our stage, for colors (brightness) that is not on our stage?"  You're using "science" as a reason not to really think about this stuff.  Again, maybe I'm wrong, but I haven't heard any argument against what I see.  

Another way of looking at it is that when you say you shoot everything LOG it's like a photographer saying they shoot everything 1600 ISO and when you challenge them on it they say they really know how to "use it and apply noise reduction expertly."  Would you want photographs from such a photographer?  Of course not (unless they're shooting a scene where deep shadows are more important than the general exposure).    When you shoot S-LOG you are also shooting high ISO in a way.  Why would you ever want to do that in a scene lit to perfectly fit the gamut of people's displays?

If you want to see for yourself, light a scene within 6 stops and shoot both in a normal profile S-LOG and see for yourself.  

I don't actually shoot S-LOG all the time. 

In a situation where 14 possible stops would spread the data too thinly (low light), I'd opt for a hyper gamma mode, where highlight roll off has a bit more control yet the image retains a lot more info into less stops. 

For the TV scenario, well, it really spends on what you're shooting, the lighting design, the style - on what camera and setting I'd choose. Is there are big 5k Arri coming through the window, and 150w Dedolights providing a kick for the actors face? Or is everything lit with Kino 4-banks at high key? Are there lots of colour variants, or is it just consistent tungsten? All these choices determine what the best profile to use for the project. 

I've had a lot of my music work on TV, however I've only shot primarily for TV once. They wanted SLOG-2 4K ProRes 422, yet would also accept SLOG-2 4K from the A7SII and A6500 as B/C cams! (This was BBC3). The variants in location was staggering, but they just wanted a consistent, grounded film look. 

Whilst I do pay attention to the technical side, the look is most important. SLOG gets that look for me, so despite its shortcomings in colour, it gets the look I want much easier than standard Rec709 profiles. 

 

Share this post


Link to post
Share on other sites
56 minutes ago, Oliver Daniel said:

I don't actually shoot S-LOG all the time. 

In a situation where 14 possible stops would spread the data too thinly (low light), I'd opt for a hyper gamma mode, where highlight roll off has a bit more control yet the image retains a lot more info into less stops. 

For the TV scenario, well, it really spends on what you're shooting, the lighting design, the style - on what camera and setting I'd choose. Is there are big 5k Arri coming through the window, and 150w Dedolights providing a kick for the actors face? Or is everything lit with Kino 4-banks at high key? Are there lots of colour variants, or is it just consistent tungsten? All these choices determine what the best profile to use for the project. 

I've had a lot of my music work on TV, however I've only shot primarily for TV once. They wanted SLOG-2 4K ProRes 422, yet would also accept SLOG-2 4K from the A7SII and A6500 as B/C cams! (This was BBC3). The variants in location was staggering, but they just wanted a consistent, grounded film look. 

Whilst I do pay attention to the technical side, the look is most important. SLOG gets that look for me, so despite its shortcomings in colour, it gets the look I want much easier than standard Rec709 profiles. 

 

Again, that last thing I mean to do here is question your creative skills, which are immense.  I can understand why BBC might want S-LOG if "the variants in location was staggering", but does that change the fact that IF you were shooting in all controlled 6-stop environments you wouldn't touch S-LOG with a 15 foot pole?  Nor would they want you to?  What you're talking about is quite fascinating to me, all the variables that go into choosing your profile.  If you say the loss in color fidelity is worth the extra dynamic range, then I believe you!  But how does another filmmaker on the forum, like me, put that into practical use?  I don't shoot every day like you do.  I can't eyeball the scene and know from hours of camera use what profile will get me the look I want?  Which brings me back to my point.

Professionals use S-LOG, which is very tricky, to tame high DR scenes which they CANNOT control.  Why would anyone, in control, light a scene beyond 6 stops?  Even if they wanted noise, they could simply underexpose!  So shouldn't the first goal of anyone be to get a scene as tightly lit as possible?  

I understand the S-LOG is fun, and I understand why one wants it.  Again, I'm no here to pick a fight, I sincerely struggle with this issue myself.  I want to find a solution for me.  But when I see people on YouTube who show graded S-LOG in a scenes under 6 stops of light I just don't get it.  It proves nothing because S-LOG isn't made for that environment--again, it's misleading!  Those image data from a standard profile, in those scenes would have up to 30% MORE COLOR!

Let me say again how I understand things.  Digital sensors have a sweet spot of light sensitivity at a certain stop, at a certain ISO.  So if your first stop is 100 ISO, your second stop, in DR, is at 200 ISO, your 3rd stop at 400 ISO.  4th, 800, 5th, 1600, 6th, 3200.  There IS noise in light that hits the sensor at its 6th stop, it's just not very noticeable.  If, like you mention, you have some 5K Arri coming through the window and you don't want it too overexposed, you might shoot an S-LOG that is 10 stops out.  That means you're moving the lowest stop to account for the Arri, putting your top stop at 48,000 or something like that.  It really doesn't matter if you're shooting 8, 10 bit H.264 or RAW, THE PHYSICAL LIGHTING drives your decision in having to use S-LOG and it means, ultimately, that you have to use noisy image data to get contrast.

Many people on the Internet talk about S-LOG as if it is a fix-all for all lighting.  That's what drives me bonkers.  Is it?  Yes, it fixes certain high DR physical scenes into a look one may want, but it would also DESTROY the quality of a scene in 6-DR lighting.  To me, the FIRST GOAL is a noise-free image, fully saturated image, in the DR that will eventually reach the viewer.  Again, they never see anything beyond 6 DR, period.   So I don't understand why you don't say, I only shoot S-LOG when I have to.  Why isn't your first goal shooting a scene that optimizes the image capabilities of your camera, which, no matter how good, still struggles a little bit at 6 stops outs?

Just want to repeat, not questioning your skills, but what are your "first principles" as a cinematographer ;)  I know it is to get the best look for your client, but before that, don't you want the best image?  That's part of my OP, that S-LOG has made many people lazy about how they approach the photography aspect and it may hurt them in the future.  For example, someone shoots S-LOG in a 6 DR scene, then on monitors in the future that are more color rich, the footage looks very washed out and noisy compare to other cinematographers who shot the profile that maximizes the camera's capabilities in a 6 DR range. 

 

Share this post


Link to post
Share on other sites

I don't own a Sony, and I've never shot Log, but most of the videos I enjoy online have muted palettes and low saturation, so I guess from an artistic standpoint, I'd choose log too if I had it. I don't care for fully saturated images most of the time, though of course, I've seen some great films with super saturated colors. 

 

Share this post


Link to post
Share on other sites

Okay, I've skimmed through some of the comments here and hopefully I can add something helpful/useful and clear some things up for everyone here.

Quote

My current conclusion is S-LOG is not really about dynamic range, unless you interpret that as capturing only brightness values in the wild.  S-LOG is a "look".  I'm personally tired of it, but that has no bearing here.

S-Log, Alexa Log C, Canon C-Log, Redlogfilm, Bolex Log, BMD Film, V-Log, all the Cineon-type log specifications on modern cinema cameras were designed for exactly that purpose. The main goal of having these color spaces (consisting of mainly a color gamut and an optoelectronic transfer function, and sometimes a little more) were the following:

  1. Retain most amount of detail possible through digitization, bit reduction, and/or compression.
  2. Integrate/mix footage with motion picture film (Cineon) and other cameras.
  3. Consistency and mathematical accuracy, which translate to less guess work.

And I think there's some misconception that these log specifications were designed to be looks. Yes, they have a look designed in them/inherent to them, but that is not their main function. By retaining the most possible detail you're able to reproduce scene referred data more accurately, which means you can color with everything the camera was capable of seeing/capturing. So, while there is a bit of 'lookery' happening with these color specifications, their main purpose is to retain data.

Quote

When one shoots S-LOG, aren't they walking away with more noise than accurate color values in which to apply the LUT?

No. All else equal, any noise in an image recorded in a log color space will be present in that image when viewed in another color space. These color transforms can't add or subtract noise from an image, only change the appearance just like every other bit of signal.

Quote

Will S-LOG look very dated and washed out in the future?

Not sure what you mean by dated, but as long as you're viewing wide gamut or HDR data on a display with a gamut lesser in size or more restrictive transfer function, it will look desaturated and low contrast.

Quote

Why isn't there more discussion of the destructiveness of S-LOGs on color data?

Log specifications are not inherently destructive. Bit reduction and compression, however, are destructive (in most cases).

Quote

The question is, isn't it a misnomer to say LUTs put the color back in?

The data is already present in the image. A LUT is literally just a quantized representation of a color transform (continuous functions like our log specifications). So all it does is change the appearance of the data that's already there.

If further explanation is needed, I'd be happy to oblige.

Share this post


Link to post
Share on other sites
On 7/9/2017 at 6:22 AM, maxotics said:

I understand the S-LOG is fun, and I understand why one wants it.  Again, I'm no here to pick a fight, I sincerely struggle with this issue myself.  I want to find a solution for me.  But when I see people on YouTube who show graded S-LOG in a scenes under 6 stops of light I just don't get it.  It proves nothing because S-LOG isn't made for that environment--again, it's misleading!  Those image data from a standard profile, in those scenes would have up to 30% MORE COLOR!

 

No. Small gamut does not equal more data.

Okay, this isn't exactly the best representation, but this is the line of thought that I came up with when it clicked for me. Disclaimer: it is literally a childish example. So I apologize in advance haha

Color space is a sandbox and data is your sand.

Say we have a sandbox of arbitrary size and our current point of reference. We start to fill it with sand up until just after one single grain of sand spills out of the boundary of the sandbox. This would represent an image with colorfulness at its highest level and a linear lightness that gets mapped to 1.0 or 255 or 1023 etc.

Let's fill the sandbox with more sand so that it spills overwhelmingly out to the side. But, we can't play with that sand because it's outside our sandbox.

Now we're going to build a sandbox encompassing the spill and the other sandbox; far enough out so that there is a good amount of space between the boundary and our sand. Our point of reference is still the smaller sandbox, so even though it's the same amount of sand in and around the small sandbox, occupying the same space, it looks like a lot less sand because of the size of the sandbox (sorta the same idea of using smaller plates when eating. The same amount of food on a small and large plate will look like 'more' on the small plate). This is the same has having a wide gamut or HDR color space. Since most of us have a point of reference that is small, a relatively small amount of data will look normal or well saturated and contrasty. And what we would consider a relatively or exceedingly large amount of data in our small color space would look desaturated and low contrast in a wide gamut or HDR color space because the data is 'small' relative to the size of the larger space.

Hope this makes sense.

Cheers

Share this post


Link to post
Share on other sites

I learned a couple of things from this thread. Sandbox explanation works. I also like the explanation that S-log sacrifices colour information for detail and highlight retention. I feel like smoother highlights and shadows is more important than colour for the majority of scenes. Thanks guys!

Share this post


Link to post
Share on other sites

This is a great thread.

I've been experimenting with colour profiles once again on the A7SII after settling with the GFILM recipe for SLOG2. I tried out PP Off and Cine 4, and what I couldn't get away from was that SLOG2 produces a certain look and texture that the other profiles simply can't match. Perhaps on one or two shots you could get close, but for most, there's a tonal graduation that is unique to LOG profiles. 

Yes, when I zoom into an image, there's more colour noise, but I can live with that given that the image as a whole is much more pleasing, more film-like when compared to the Cine gammas or PP off. 

Share this post


Link to post
Share on other sites

Does anybody here have both an A7SII and an A6500? I know that the latter is a little sharper, but how do they compare when it comes to S-log, quality of the image, etc? Is the A6500 rolling shutter so bad that you can't use it on a gimbal with fast moving shots?

Share this post


Link to post
Share on other sites
5 hours ago, Amro Othman said:

I learned a couple of things from this thread. Sandbox explanation works. I also like the explanation that S-log sacrifices colour information for detail and highlight retention. I feel like smoother highlights and shadows is more important than colour for the majority of scenes. Thanks guys!

Like I said with the sandbox example, you don't lose color information when using a log color space with wide gamut. It's literally the opposite. Wide gamut stores the most possible color information. These curves just change where the data is mapped. The log curve redistributes linear data so that the shadows and midtones are more likely to keep detail through quantization and compression.

The only things that will cause you to lose information are the aforementioned quantization and lossy compression.

Share this post


Link to post
Share on other sites
20 hours ago, iaremrsir said:

No. Small gamut does not equal more data.

Okay, this isn't exactly the best representation, but this is the line of thought that I came up with when it clicked for me. Disclaimer: it is literally a childish example. So I apologize in advance haha

Color space is a sandbox and data is your sand.

Say we have a sandbox of arbitrary size and our current point of reference. We start to fill it with sand up until just after one single grain of sand spills out of the boundary of the sandbox. This would represent an image with colorfulness at its highest level and a linear lightness that gets mapped to 1.0 or 255 or 1023 etc.

Let's fill the sandbox with more sand so that it spills overwhelmingly out to the side. But, we can't play with that sand because it's outside our sandbox.

Now we're going to build a sandbox encompassing the spill and the other sandbox; far enough out so that there is a good amount of space between the boundary and our sand. Our point of reference is still the smaller sandbox, so even though it's the same amount of sand in and around the small sandbox, occupying the same space, it looks like a lot less sand because of the size of the sandbox (sorta the same idea of using smaller plates when eating. The same amount of food on a small and large plate will look like 'more' on the small plate). This is the same has having a wide gamut or HDR color space. Since most of us have a point of reference that is small, a relatively small amount of data will look normal or well saturated and contrasty. And what we would consider a relatively or exceedingly large amount of data in our small color space would look desaturated and low contrast in a wide gamut or HDR color space because the data is 'small' relative to the size of the larger space.

Hope this makes sense.

Cheers

I never said a small gamut equals more data, did I?  I don't understand your analogy, though others seem to.   I'll try to explain what I'm saying using your metaphors.

Yes, the sandbox equals our data space, we can fit 16 million colors into our sandbox.  Our gamut is essentially how far apart the colors are, from one piece of sand to another, arranged from darkest to brightest.  Perceptually, the gamut MUST match the sandboxes distribution or it will look wrong to us.  I want to point out, that I haven't made clear in other posts, that there are no real colors in our sandbox.  There are only grayscale readings (brightness) from sensor pixels with known color filters in front.  The Gamut (and other matrix calculations) is what translates those colors into a brightness/contract/saturation whatever scale that makes sense to us.  Because sensors have their own oddities, and our vision also had idiosyncrasies,  we don't just make a red with a value of 20 double the redness of a value of 10, or if we do, it doesn't mean that we make the value of 80, a double of 40.  

If you take sand from outside your sandbox then yes, you MUST change the gamut to match what we expect visually.  Unfortunately, S-LOG introduces another way of thinking about gamut, not as a way of making visual sense of image data, but as a way of taking full-color data outside a 24-bit space and re-jiggering it AS IF it fit in the sandbox in the first place.  THE PROBLEM is that data outside the 6-stops of expected gamut, which are put into our sandbox, are at higher noise than those from our original sandbox.  Noise is what makes us get less color which again, are ONLY RELATIVE BRIGHTNESS values that the sensor picks up.  

Put another way, let's talk about red only.  In a standard profile you're getting 1 to 255 shades of red.  The values at the low and high end are noisier, more uncertain, than the values in the middle, say at 127, because that is the nature of all scientific sensors.  The actual red you make out of those values in up to you.  You can get someone's LUT for example, and assign them accordingly.  When you shoot S-LOG you're getting sand outside your sandbox, as you say, but what you're not recognizing is THE QUALITY OF THAT SAND is poor.   Wide gamut, HDR, all these ideas will not change that very simple fact. 

You can test this yourself as I did (at the end of my video).  The quality of your data is the number of distinct colors you get because again, they have no real color, that is assigned afterwards based on your assumptions of how the data is distributed.  You get 16 million distinct colors in a standard profile and only 10 million distinct colors in an aggressive S-LOG.  You can distribute those 10 million colors to make an image that more closely matches the wide dynamic range of the original scene, in basic contrast only, BUT, and I say this again, AT THE EXPENSE of color information.  

You may be reading this and thinking, 'well, if I follow your argument why would anyone use S-LOG."  Because in lighting they can't control S-LOG can give them contrast they can't get in a standard profile.  Again, I HAVE NOTHING against s-log.  I'm just pointing out that a lot of people doesn't seem to understand WHAT THE TRADEOFFS are.  So I don't understand what you're saying on the level of how you think you can extend the sandbox without real consequences and that the first goal should always be to light your scenes to fit a 6-stop sandbox.  When people suggest to new filmmakers that their footage looks bad because "they don't know how to use S-LOG" I disagree strongly.  Even when used perfectly, S-LOG is NOT BETTER than a 6-stop scene lit to get EXACTLY the look you want in a 6 stop range which is what EVERYTHING ENDS UP IN.

11 hours ago, iaremrsir said:

Like I said with the sandbox example, you don't lose color information when using a log color space with wide gamut. It's literally the opposite. Wide gamut stores the most possible color information. These curves just change where the data is mapped. The log curve redistributes linear data so that the shadows and midtones are more likely to keep detail through quantization and compression.

The only things that will cause you to lose information are the aforementioned quantization and lossy compression.

 Prove to me it is "literally the opposite."  Wide gamut store wider values in a physical scene but those wide values are of poor quality.  Because you always end up in a 6-stop space, why not get those values in a standard gamut?  That's what you're not thinking about.  CAN YOU GET any look you want IF you could control the light in every situation to 6 stops?  Yes, you can, which is why big-budget film crews have huge trucks of light modification equipment.  THEY KNOW a film shot in 6-stop light will look better than wide gamut in 10 stop light.  S-LOG is for when you CANNOT afford to light everything perfectly.  Or you're run-and-gunning and you don't have the time, etc.

 

Share this post


Link to post
Share on other sites
12 minutes ago, maxotics said:

I. Put another way, let's talk about red only.  In a standard profile you're getting 1 to 255 shades of red.  

I'm afraid you're confusing bit depth (in this case, 8bit with its 256 shades per color channel) with color profiles.

I think it's easier to draw a simple analogy between dynamic range and image resolution:
A Log-Curve does the same thing for dynamic range that an anamorphic lens does for image resolution: It squeezes/compresses a larger bandwidth of visual information into a lower-bandwith medium. (In the case of an anamorphic lens, a wider image into a narrower frame, in the case of a log curve, a wider dynamic range/palette of colors into a narrower palette.) 

Desqueezing the image can easily result in ugly artifacts if your resolution is limited:

- if you record 2:1 anamorphic in 1920x1080 and desqueeze to 3840x1080, you will end up with blocky/doubled pixels on the horizontal axis. You wouldn't have those artifacts if instead you recorded in 4K for desqueezing into 3840x1080.

- if you use a log curve to squeeze 12 stops dynamic range into the linear 8 stops supported by an 8bit codec, you will end up with a torn curves in the histogram and blocky color gradients when desqueezing the color back into 12 stops. You wouldn't have those color artifacts if instead you had had 10bit color depth for your log curve recording.

This is why, with an 8bit camera (and supposing that it has perfect 8bit Rec709 color science), it's preferable to record scenes with a contrast ratio of 1:255 (=8 stops) or less in Rec709 instead of Log.

In reality, consumer and prosumer cameras implement all kinds of crowd-pleasing processing gimmicks in their Rec709 profiles (such as artificial sharpening, denoising, color shifts and contrast enhancement) but have them switched off in their Log profiles, so that many people end up using Log profiles for a less artificial, less-consumer-videoish, more organic-looking image - although this may come at the price of color banding artifacts and generally less color depth. After desqueezing 8bit log into Rec709, you probably end up with 7bit or 6bit actual color depth, just as desequeezing 2:1 anamorphic from a 1920x1080 recording into 1080p will half your pixel resolution.

Share this post


Link to post
Share on other sites
2 hours ago, maxotics said:

I never said a small gamut equals more data, did I?

But you said "standard profiles" which are narrow gamut/SDR color spaces similar to sRGB/BT.709. So, yes, you did indirectly say you get more color with a smaller gamut.

2 hours ago, maxotics said:

If you take sand from outside your sandbox then yes, you MUST change the gamut to match what we expect visually.  Unfortunately, S-LOG introduces another way of thinking about gamut, not as a way of making visual sense of image data, but as a way of taking full-color data outside a 24-bit space and re-jiggering it AS IF it fit in the sandbox in the first place.  THE PROBLEM is that data outside the 6-stops of expected gamut, which are put into our sandbox, are at higher noise than those from our original sandbox.  Noise is what makes us get less color which again, are ONLY RELATIVE BRIGHTNESS values that the sensor picks up.

You're applying a line of thought that suggests these log specifications are applied at the analog stage before digitization which is the only place that a color transform could add noise. Any noise in the raw data before color transform will be present in the image regardless of the color transform. The only difference is that the noise is pushed down further in the other color space and wiped out with any other fine details in the shadows by lossy compression. Again, compression is what gets rid of detail, more so than quantization/bit reduction. 

2 hours ago, maxotics said:

Put another way, let's talk about red only.  In a standard profile you're getting 1 to 255 shades of red.  The values at the low and high end are noisier, more uncertain, than the values in the middle, say at 127, because that is the nature of all scientific sensors.  The actual red you make out of those values in up to you.  You can get someone's LUT for example, and assign them accordingly.  When you shoot S-LOG you're getting sand outside your sandbox, as you say, but what you're not recognizing is THE QUALITY OF THAT SAND is poor.   Wide gamut, HDR, all these ideas will not change that very simple fact. 

You can test this yourself as I did (at the end of my video).  The quality of your data is the number of distinct colors you get because again, they have no real color, that is assigned afterwards based on your assumptions of how the data is distributed.  You get 16 million distinct colors in a standard profile and only 10 million distinct colors in an aggressive S-LOG.  You can distribute those 10 million colors to make an image that more closely matches the wide dynamic range of the original scene, in basic contrast only, BUT, and I say this again, AT THE EXPENSE of color information.  

You may be reading this and thinking, 'well, if I follow your argument why would anyone use S-LOG."  Because in lighting they can't control S-LOG can give them contrast they can't get in a standard profile.  Again, I HAVE NOTHING against s-log.  I'm just pointing out that a lot of people doesn't seem to understand WHAT THE TRADEOFFS are.  So I don't understand what you're saying on the level of how you think you can extend the sandbox without real consequences and that the first goal should always be to light your scenes to fit a 6-stop sandbox.  When people suggest to new filmmakers that their footage looks bad because "they don't know how to use S-LOG" I disagree strongly.  Even when used perfectly, S-LOG is NOT BETTER than a 6-stop scene lit to get EXACTLY the look you want in a 6 stop range which is what EVERYTHING ENDS UP IN.

Yes, in 8-bit you lose color resolution, but not to the extent that you are suggesting. If you've ever looked at characteristic curves of a log curve and something like linear or BT.709, you'll see that once you get to around 3-4 stops below middle gray, with a "standard profile" you're dropping detail low enough to where a codec like H.264 can smooth that detail out (which also smooths out noise and gives that plastic look or dancing blocks). But with a log curve, shadow detail is held above that threshold and is less likely to be smoothed out entirely (thus allowing you to avoid the plastic and shadow blocking). So yes, you might get more code words per stop with a "standard profile," but highly saturated colors are more likely to clip, you lose fine details in shadows, and you have a lot less room in the highlights. When you get into the mathematics of it, yes, you lose some code words per stop, but you can record more saturated colors, more highlight detail than just 2.3 stops, and detail and texture in the shadows. Even if an expert cinematographer lit a scene, they'll more often than not still have values in the deep shadows and possibly specular highlights. Of course it's not ideal in 8-bit, but nothing is.

This doesn't even touch on post production color management when knowing the specifics of the color space is vital.

2 hours ago, maxotics said:

 Prove to me it is "literally the opposite."  Wide gamut store wider values in a physical scene but those wide values are of poor quality.  Because you always end up in a 6-stop space, why not get those values in a standard gamut?  That's what you're not thinking about.  CAN YOU GET any look you want IF you could control the light in every situation to 6 stops?

You just said wide gamuts are able to store more intense values. That means they can store those more intense values that the raw data contains. Meaning they can store more colors regardless of the resolution (bit depth) that those colors are quantized into.

2 hours ago, maxotics said:

Yes, you can, which is why big-budget film crews have huge trucks of light modification equipment.  THEY KNOW a film shot in 6-stop light will look better than wide gamut in 10 stop light.  S-LOG is for when you CANNOT afford to light everything perfectly.

Yet, cinema/TV has been shot in log and more recently raw, then graded in log working color spaces for decades.

Share this post


Link to post
Share on other sites

@cantsin and @iaremrsir you keep trying to explain this to me as if I just stumbled upon video technology, as if I haven't written software that works with RAW data.  I can't force you to think through the ramifications of S-LOG. 

I feel you keep bringing up issues that obfuscate the core question.  What does compression have to do with the amount of noise in sensor data or 8-bit color spaces? Nothing!  

You wrote, "You're applying a line of thought that suggests these log specifications are applied at the analog stage before digitization"  YES I AM!  Though not in the way you say because "log specifications" are not a thing you apply in one place or another.  ALL DATA must be married to a curve in the end.  Where you think that curve should be applied is a philosophical one.  You talk about it as if it is some tool.  What I AM SAYING is that S-LOG pulls noisy data from the sensor outside the bounds of what it is engineered to do best and what its physical limitations are.  It has nothing to do with whether it is before or after digitization.  In a sense, you keep arguing that S-LOG can fix noisy data.  I say it can't.  

I never said Cinema/TV doesn't use S-LOG.  Where did I say that?  And I certainly NEVER, EVER said it has been used in RAW because that is flat-out non-nonsensical.  I would also never say "graded in log" because that is the same as saying "graded in graded" because you cannot do much grading without changing a curve.  Again, curves, LOG or linear, are all arbitrary applications of sizing on brightness values to create a subjective perception of contrast.  Don't you see that when you work with curves in your NLE all day it's easy to believe it's a tool?  I understand where you're coming from.  Which is why you need to work harder in thinking about how the image data gets to your NLE and how what you tell the camera to do, how to capture the data, what I'm calling its default "standard profile" or S-LOG, has different effects on the image then what curve you choose in post.  If the camera manufacturers had called S-LOG what it really is, mixed ISO shooting there might not be so much confusion.

Again, if you get the results you want using your workflows, great!  In the end, that is ALL the matters.  But that doesn't mean what you do will work for the next guy.  Arguing that the other guy doesn't need mid-tone values because S-LOG can do this or that is, to me, artistically arrogant and indicative of a half-baked understanding of photography.  I am NOT saying you're a bad filmmaker because you use LOG, far from it!  But I will call anyone, even Oliver, on an argument that one can make S-LOG do anything if they know what they're doing.  If that' is true, I want to know how!  But you have to tell me how you get around the physics of image capturing as it exists today.  I have only heard rationales for the trade-offs, not reasons why S-LOG is always preferable.

The only thing I have learned so far is that S-LOG has become sort of a lowest common denominator of image quality that prioritizes capturing wide DR in the real world over better color saturation, that the camera is capable of, in scenes lit to maximize the camera's potential.  

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...