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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Shooting in log?

macgregor said:
In the end, we should be all talking about zone system, and not so much about ISO. Where do we want to set our 18% grey is the clue.
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Macgregor, are you saying that you got 9-stops of exposure latitude with your Red? That would be about the same latitude as film, which I don't think Red is even claiming.
 
Mac, that just makes no sense to me.

Everyone swears that the Red can't be underexposed by more than about a stop below the 18%-gray-to-45-IRE standard without displaying undesirable noise.

Rec709, plain and simple, only encompasses two stops over 45 IRE, even if you consider 110% to be the clipping point.

Underexpose that by a stop and add the +0.4 stop of headroom at ISO 320 and you get 3.4 stops, let's be generous and round up to 3.5.

Something tells me we're not going to see a clean seven stops below middle gray when underexposed by a stop.

So I must say that I highly question the 11 stops thing.

-Stu
 
ProLost said:
Mac, that just makes no sense to me.

Everyone swears that the Red can't be underexposed by more than about a stop below the 18%-gray-to-45-IRE standard without displaying undesirable noise.

Rec709, plain and simple, only encompasses two stops over 45 IRE, even if you consider 110% to be the clipping point.

Underexpose that by a stop and add the +0.4 stop of headroom at ISO 320 and you get 3.4 stops, let's be generous and round up to 3.5.

Something tells me we're not going to see a clean seven stops below middle gray when underexposed by a stop.

So I must say that I highly question the 11 stops thing.

-Stu
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The 11-stop figure comes from measuring the RAW conversion to RGB LOG, but not necessarily in Rec709 space... but are you sure that there are only two stops between 45 IRE and 110 IRE? That sounds like each stop equals a jump of 30 IRE...
 
I'll jump in as we've been doing our testing as well... in comparison against our vipers , and our F23's (also soon to add a D20 into the testing mix hopefully). Right now we're pegging the red at 8 stops, Viper at 9-10, and F23 at 11-12 depending on lighting conditions. The big thing I want to point out is that from working with Viper footage for so long is that everytime the viper was treated like a film camera its turned out rather wonderfully, every time its been treated like a video camera I won't name names but its looked bad.

The same holds true for the red. So I'm going to vote with Stu a log based output is really important, because we can then in the monitor, a Luther, or a whatever create in LUT a more true representation of what will hit the Theatre screen.

One last thing, I've noticed and I'm going to say it rather obnoxiously, screw shooting Rec 709. It looks bad. The green is mint and the reds make you think of pepto bismal. If you're looking at an approximation it should be a useful one. If you want to see what I mean I can show you on our barcos I have two buttons P3 and Rec 709, no you won't see it anywhere else but by having that inherent level of quality in your data it shows in what you're finally able to achieve even if you only have dvd release.

Ok done with Rant, I have seen all 4 of the above cameras be absolutely beautiful, and its exciting as hell.
 
Jeff Brue said:
The same holds true for the red. So I'm going to vote with Stu a log based output is really important, because we can then in the monitor, a Luther, or a whatever create in LUT a more true representation of what will hit the Theatre screen.

One last thing, I've noticed and I'm going to say it rather obnoxiously, screw shooting Rec 709. It looks bad.
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In my estimation, and I could be wrong, if Rec 709 output is not in correspondence with the log output data, then it is Red who is to be blamed and not Rec 709. It appears to me that they chose a white point for Rec 709, shy of some highlight headroom (I think somebody from Red said 0.4 stops), hence, any signal values above that point which Red chose to make threshold for the Rec 709 white point is mapped to the same value in Rec 709, where as they can easily map those values to "above white" in the log data.

Hence, any extra information you are seeing in the log space vs. Rec 709 space is the dependent upon what signal value Red chose for Rec 709 white point and how they treated any values above it.

I would tend to think that Red could have incorporated or "rolled off" that extra highlight headroom in the Rec 709 space by moving the white point, and made people monitoring/metering using Rec 709 happy.

It is important to realize this difference, and not universally bash Rec 709 space. It is a particular implementation of Rec 709 space a camera manufacturer chose to implement to blame and not the space per se.
 
The default setup for output is over-exposed by 0.4EV. If you set exposure to -0.4EV, the output is full range.

The 0.4EV headroom is in there to protect the highlights by making the image appear a bit brighter, forcing a little under exposure.

For post manipulation, I'd argue that REC709 gamma curve is more suitable than log as it looks "more reasonable" on a monitor without correction, and if used full range, carries the same range, with enough precision, and it's an international spec that you can look up and implement, whereas "log" is different for everything that does "log". RedLog, for instance, is defined as it is, knowing the precise values of the dataset that gets mapped into the log space - similarly Panavision and Grass Valley choose their own curves based upon knowledge of their sensors and image processing.

Graeme
 
If you're naming nodes, I'd suggest they be called "log to linear light" and "linear light to log" and also have a "linear light to video gamma" and "video gamma to linear light" set too. When people say "lin" I have no idea what they mean - it's totally ambiguous. I'd be happy if I never hear "lin" or "linear" again, and only hear "log", "video gamma" and "linear light", which are a lot less ambiguous.

Maybe Stu and I should set up a petition, or we should put a "lin" swear box in the Red tent at NAB?

Graeme
 
ProLost said:
Mac, that just makes no sense to me.

Everyone swears that the Red can't be underexposed by more than about a stop below the 18%-gray-to-45-IRE standard without displaying undesirable noise.-Stu
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Exactly, and that is what i said and displayed on the graphic one page ago. THe last 4 stops (shadows) display a lot of grain, so you want to avoid them as much as you can. Therefore, if you move your 18% grey to that zone (underexpose from the "original" 320ISO) your images will look BAD.

I think we are talking about the same thing here.
 
macgregor said:
Now, RED has more than 8 stops. The question is how much noise are you willing to accept on your film.
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What's the motivation to peg RED at 8 stops?

If you're The Camera House and you have Vipers and F23's that you own, would you really want people to rent RED before your high cost items? Does TCH own any REDs or are they on consignment?
 
Yes we have Reds coming in yes we rent them, yes we like them. Motivation well... when you get into high end digital aquisition and you really start looking at the cameras (which we're in a position to do) you'll realize each sensor is like a film stock. They each have their strengths and weaknesses, its our job as a rental house to present those differences and let the film maker decide.

Personally I think the viper has the best color range, I think the F23 can reach further into highlights than any camera out there, and Red has an amazing amount of detail and can not be beat on the price point, and opens up a wonderful new market. Not to mention that it is the ONLY 35 mm type sensor that takes our film lenses, currently available to buy.

On the same note the viper can't speed ramp, the F23's reds are orange, and the red (still) has too much compression and film out is a battle when material is shot looking at a rec 709 on a vectorscope.

Stu didn't say anything new to us here, the thing is I've seen Red in the last few months change this camera rather drastically, so I don't like shouting about anything until they say 1.0. They should be given for the first year the benefit of a doubt, god knows every other first gen DAQ camera has.

Lastly, yeah I will universally bash Rec 709, I think its another case of engineers compromising in committee which always leads to a least common denominator, in order to tell everyone they mush upgrade their TV's every 3-4 years. xvYCC is already out there and works.
 
mmost said:
Not if you feed it to an external monitor that can either implement a view LUT (like a Cinetal) or a box that does the same thing (like a LUTher). I can't speak for Stu, but that could be what he's thinking here: a way of getting a reasonable film print preview during production. This is a common way of working with cameras such as the Viper and Genesis.
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Hello All,

I'm a Toronto based DP that is about to test the RED. I must admit, not having a live RAW logarithmic preview on set is a major issue for me. I've shot on the Viper with a Film-out in mind, and I'm constantly monitoring the FILMSTREAM output. I'm essentially checking what I'm exposing on the "digital neg." As also mentioned in this thread, putting this signal through some kind of "print emulation" (luther etc.) is also a must in my mind in your going to print.

cheers

luc
 
ProLost said:
mmost: Yes, although I'm also simply concerned with the exposure habits of video creating images that aren't filmout friendly. This will be the topic of the blog post, so stay tuned.

Deanan: Thanks for jumping in. Long ago I asked Graeme on this forum if RED Log could be documented so we knew what was going on with it. I don't suppose you could shed some light on the actual formula?

Based on the published information about Genesis Panalog (the tell you where black, white and 18% gray fall) I was able to reverse-engineer matching settings for the log-to-lin nodes in most compositing apps: link

I'd love to do the same for RED Log if possible.

-Stu
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Graeme sent this in a reply to one of my posts, and later said he was still deciding on how to tabulate stuff for developers to someone elses, his post to me went

"The log curve is of the form y=A * log(B*(x+C)). It's not a spline based curve at all. By altering A,B and C you can get a whole family of nice curves that obey the properties we need."

I`ll be pressing for more details when the strain is lifted from the Red dev team a little, if the sdk`s I hope they`ll release don`t deliver, but I`m sure they will, as I know nothing about log data till I do lots of reading!!
 
I crazy thought crossed my mind.. Jim Jannard signs up Stu to join the red team. hehe. unlikely but interesting thought.

A message to Stu, love your blog.. if you ever compelled to write a red related manual/book, I'd buy it in a heartbeat.
 
Graeme Nattress said:
If you're naming nodes, I'd suggest they be called "log to linear light" and "linear light to log" and also have a "linear light to video gamma" and "video gamma to linear light" set too. When people say "lin" I have no idea what they mean - it's totally ambiguous. I'd be happy if I never hear "lin" or "linear" again, and only hear "log", "video gamma" and "linear light", which are a lot less ambiguous.

Maybe Stu and I should set up a petition, or we should put a "lin" swear box in the Red tent at NAB?
Click to expand...

I use "lin" all the time, but only to describe linear light. I wish everyone else would do the same. Seeing gamma-encoded video referred to as "linear" makes my skin crawl.

-Stu
 
I'd like to use "lin", but it has become meaningless through misuse. That's why I have had to start to say linear light, to emphasize the point. And yes, referring to gamma encoded video also makes my skin crawl....

Graeme
 
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