The power of sLog - and why i'd pay $6,000 for it.......

SLog is a gamma curve like cinegamma, its just very aggressive. The differnce is that the hardware behind it is VERY powerful, so color accuracy and its ability to "See" more of the sensor is higher. In a way, its like raw, in that its all the sensor data in one place, the difference being raw, is just the analog signal from the sensor, unprocessed, recorded to redcode.

Slog is raw sensor data, converted to a vsible form then recorded to uncompressed/prores/cineform etc.....

They are similar in a loose sense.
 
starcentral said:
Can you please school me on how SLOG is not equivelant to RAW?

(Just looked up Cinedeck rental rates, $250/day, $1000/week)
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RAW is before debayer so pixels are not RGB, and redcode is wavelet compressed RAW so debayer still needs to happen.
Red mentioned that they may bring out a version called redcode-RGB which would be for an in-camera 1080p debayer option.
Best way for you to understand is to play with a RAW file from a DSLR still and put it through the debayer process on your computer
 
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Thanks for the explanations, that is helpful. I see they are loosely similar.

Timur, a couple of questions:

- Have you drawn any conclusion on how far you can push/pull 420 footage (in stops) before it really starts falling apart? (ie. introducing noise or artifacts)
- The F3 outputs 422 via SDI dual link without the SLOG upgrade, so what diffrence is it to have SLOG 444 but record using AJA KI PRO which is only 422?
- To the previous point, isn't it just as well to record 422 from the F3 and have the same results you did in your tests?
 
starcentral said:
Thanks for the explanations, that is helpful. I see they are loosely similar.

Timur, a couple of questions:

- Have you drawn any conclusion on how far you can push/pull 420 footage (in stops) before it really starts falling apart? (ie. introducing noise or artifacts)
- The F3 outputs 422 via SDI dual link without the SLOG upgrade, so what diffrence is it to have SLOG 444 but record using AJA KI PRO which is only 422?
- To the previous point, isn't it just as well to record 422 from the F3 and have the same results you did in your tests?
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i can fill in a few blanks.

A. 420/422/444, pushing in luminance will all be the same if they are recorded to the same way to the same codec. color space has nothing to do with luminance, but effects more of the general feel and look because the areas with color and light will vary up in color information and effects subtlety of how skin tones, and other portions of the image look. but it doesn't effect dynamic range or sensitivity.

B. same answer as A, no difference in luminance, it's all about actually pushing the color, 444 you have a lot more control, and can create really subtle changes with really smooth movements in your color spectrum. letting you dial in very fine things if you so desire.

C. yes, same results luminance wise, refer to A, and B :)
color space is just that and only that.
 
Timur,
Great test. Thanks

Question, why test against rec 709 instead of the cinegammas? The 709 180% is clearly inferior to both the s-log and cinegammas.

The question I have is how do the cinagammas hold up against the s-log when both are exposed properly for the individual curve and recorded to prores HQ? It seems like a logical comparison.

I have seen a lot of test where simultaneous footage was pulled of the sxs card but exposure favored the s-log and was recorded to 420.

Again, thanks for the test.
 
Timur, tell me more about the monitoring of the image when you shoot and getting proper exposure. It seems that it would be easier because of the range to get a proper exposure but it sounds like that isn't the case. How difficult is it getting the proper image and exposure using the camera settings and external monitor?

I plan on upgrading to S-Log and using the PIX240 to record at 4:2:2. How difficult or easy will it be to monitor the image and exposure using the onboard camera waveform, zebra and external monitor.
 
The draw back of using a single sdi is that you lose LUT support.

However exposure is just like normal, you just have to understand how LOG works. its compressing in the lower range blow 40 IRE to about 10 IRE, 7 stops of the lattitude with middle grey at 35IRE, and above 40, from 40-110 the top 6 stops.

just know where you're middle grey is supposed to fall and you can use false color, or a wave form to set your exposure on the Log itself. in fact, viewing the log, is great cause you can see EXACTLY whats burning out and what isn't. you just have to understand how its going to change when you de-Log it. This is advanced Hollywood exposure stuff. you REALLLY have to understand your exposure and what you can put where. Go to far down and you get muddy blacks, to high and the image looks to bright and unnatural.

In the video, the shot of mark harris, i intentionally under exposed in LOG, and as you can see its muddy and dark when delogged. where as the shot of the overpass, and Tom walking into the sun, is very carefully exposed and thus you can see how beautiful it can be. Its almost like film.... its better to slightly over expose than to slightly under expose.




*actually..... i need to triple check the 35IRE middle grey on Sony sLog. it may be 40 now that i think about it....
 
You say that, like film, it is better to over expose than to under expose. Using the zebra for whites what would you suggest for peak white? IRE for skin/face?
 
I'm figuring this out now... but it seems that slight over exposure is easier to recover than slight under.

Actually, ***Paging TOM****, Whats easier bringing down slight over, or bringing up slight under?
 
it's a tricky question, honestly there's no right answer, it's dependent on the shot, how it's lit, what the tonal range is like (where the light is, how much light you have) and amount of native contrast in the shot as is. bring down from slightly over will eliminate noise, but you run the risk of milking out your dark end too much and have to overcrush your blacks to get something rich and contrasty out of it. go slightly under and you risk gaining up too much and introduce more noise to your image. It's always tight rope, but the codec really helps with how thick that rope is. pro res is pretty good, not the best, but pretty good. I'd personally prefer if you can do it, to go slightly over so I can bring it down because i'm a noise Nazi, but you'll probably end up with a more natural looking image right off the bat if you go slightly under and bring it up since the darks are landing really close to where you want them to be already.


that's why it's important in log workflows to be able to LUT on set and see what you really have. And working with it day in and day out, you'll develop a instinct for how you need to expose. Just like veteran DP's with film who don't even need to meter anymore. they see it with their eye and know how the film will react exactly.
 
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As I understand, if I use S-Log in 422 I won't get the benefit of LUT. So how much more difficult will this make getting proper exposure? What will I be seeing in the monitor?
 
When working with RAW, I usually go about one stop under-exposed to retain more highlight information... but that is a one stop under exposure from the native iso of the chip... now that isn't SLOG, but I'd think the same train of thought should apply, no? What is the ISO you shoot SLOG at on the F3? If you're already pushing with ISO, I can see how over exposure and pulling in post would be better for noise... but if shooting F3 not pushed, isn't there room for underexposure and push in post?

Timur, when is the next time you are in LA?
 
D10S said:
As I understand, if I use S-Log in 422 I won't get the benefit of LUT. So how much more difficult will this make getting proper exposure? What will I be seeing in the monitor?
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you'll see the slightly milky image, you can ghetto rig it by adjusting the contrast on your monitor but that's just half of it. a huge part of my job as DIT is to paintbox monitors and do real contrast expansions to the sdi tap to see what you REALLY have, and how it's gonna look as close as you can get it on set. It won't be perfect but it's a better ball park. It may feel like a luxury to have that for most but it's part of what I do, so thus i'm a biased and would have to say it's a integral part of the workflow. if you can't do it, than I'd just say shoot as much as you can on your own time and figure out where your sweet spots are, as you do have a good elasticity in the footage, and there's a very good amount of forgiveness for your image exposure wise.



@ryan
standing iso in s log is 1600. that's 0 db. that's where you achieve the most DR. but keep in mind that the f3 actually doesn't have a even curve. if you look at it on a step chart, the f3 has never had equal amount of highlight protection, it actually has more in the bottom end because of it's great sensitivity. so let's say the F3 is a solid 13 stops of DR in log, 7 of those stops are in ur low end, and it's only +6 with the highlight retention. that's why it's so much easier to just underexpose a little if you need to, to keep the highlights, and bump it back up later with minimal to no noise penalty. however if you the situation allows it, getting your mid point a little higher and you're not clipping, allows for a cleaner looking image when you do your contrast expansion.

as stated, there's def a few stops of play around room though.
 
Ryan Patrick O'Hara said:
When working with RAW, I usually go about one stop under-exposed to retain more highlight information... but that is a one stop under exposure from the native iso of the chip... now that isn't SLOG, but I'd think the same train of thought should apply, no? What is the ISO you shoot SLOG at on the F3? If you're already pushing with ISO, I can see how over exposure and pulling in post would be better for noise... but if shooting F3 not pushed, isn't there room for underexposure and push in post?

Timur, when is the next time you are in LA?
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Log works differently. The mid point is not at 50. Its 30 - 40 ire. Its difficult to explain without showing you a waveform.
 
Hmmmmm i may be on the wrong track about exposing Sony sLog...

Been having a conversation with Alistar Chapman about this.... then i saw this:
slogwaveform.jpg


This seems to suggest skintone, which normally is a stop over middle grey, should be around 55IRE.

The issue being that The F3 has 7.5 stops below middle grey, and 6 above... so do you set for the mid point of the scale? the way LOG is traditionally exposed? or the way the waveform seems to suggest, far brighter than i feel neccesary.

hmmmmmmmm?
 
MAc whats your opinion on my findings? Yo have a bit more experience than i do w/ log.

I still feel exposing the way i did, mid grey 35, is best. Seems you do too.
 
Mid grey at 36 IRE is only about half a stop lower than the Abel chart shows. You're protecting the highlights and not really reducing your DR by much. Sounds like a safe way to go.

Timur - Did Abel have charts for over and underexposure? Would be nice to see how DR is reduced.
 
I'd say chosing your mid grey point depends on your specific scene and what you're trying to protect.

If you're shooting at mid grey 50 then you are protecting your lows more than your highs on the F3 since with SLOG it is -7.5 from mid and +6 from mid.

If you're shooting a high contrast scene then you'd probably want to protect your highs more so mid grey @ 35 perhaps makes sense.

If you're shooting "in the dark" or a very evenly lit scene maybe you want to shoot @ 50 (or even higher) to keep your dynamic range in the low end.

Having said that, different cameras will have different mid points you want to establish:

lattitude.gif
 
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starcentral said:
I'd say chosing your mid grey point depends on your specific scene and what you're trying to protect.

If you're shooting at mid grey 50 then you are protecting your lows more than your highs on the F3 since with SLOG it is -7.5 from mid and +6 from mid.

If you're shooting a high contrast scene then you'd probably want to protect your highs more so mid grey @ 35 perhaps makes sense.

If you're shooting "in the dark" or a very evenly lit scene maybe you want to shoot @ 50 (or even higher) to keep your dynamic range in the low end.
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yep. different cameras will have different sweet spots, but it's always about WHAT you are shooting. if there was a magical formula that worked every single time for everything, these discussions would be long over, and a lot of ppl including myself would probably be out of the job :)
 
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