REDSpace, REC 709, RAW View and EXPOSING

[George A.]

Hello,

I'm doing lots of tests to get to know the camera. So far I am extremely pleased - I'm using the latest version of Build 16, and I experienced no codec errors and no bugs (except a one-time booting freeze). The images coming from RED speak for themselves. All in all, I'm super-happy with the camera.

The first - and probably most important step - is deciding on the best (most appropriate) exposure in every possible scenario. I mainly use the luma histogram for that, paying attention to the stop lights as well. I use ISO 320 in almost every situation.

I found that the ETTR method (exposing to the right) works best with RED - as opposed to exposing for the middle grey, as in the film world. Therefore, in a normal scene, I am always erring as much as I can towards to right side of the histogram, at the same time making sure absolutely nothing is clipped (except in difficult high-contrast scenes or the specular highlights - dealing with them is a different discussion). Pulling everything back in post gives amazing results, with very little noise and no clipped whites (if you were careful when ETTRed)

Now for the question... the expose to the right method will get you different results, based on the monitoring space you are in (REDSpace, RED 709 or RAW View). The histograms are, of course, different from each other. My tests show that once the REDSpace histogram starts to clip, you can open the lens half a stop (approximately) until the RED 709 histogram clips. Further on, you can open the aperture an additional half a stop until the RAW histogram clips. Since I suppose the RAW View gives you the accurate data of when the sensor actually clips, then there is a difference of about one full stop between clipping in REDSpace and the actual clipping in the RAW View and the sensor itself.

The first thought was that one should monitor in REDSpace (since it just looks closer to the real scene) but set the exposure in accordance with what the RAW View is showing. Again, using the ETTR, one wants to be as close as possible to the right edge of the histogram, without clipping - and REDSpace "makes" you close up your aperture roughly one full stop, defeating this very purpose. Monitoring in RAW takes you right where you want to be, since you accurately know where the exposure is "placed" on the sensor itself.

On second though, I can see the other side of the coin. Is it really best to be right at the edge of the sensor, even if you're not clipping it when shooting? Later on in post, one might easily clip the whites when playing with timing or when transcoding to an editable format, even without touching anything at all (due to different gammas and so on). Maybe it's best to set your exposure on REDSpace or RED 709 after all - still using ETTR - (just double-checking the RAW View for peace of mind), and use that one stop difference as a buffer - making 110% sure you don't clip anything, or using that buffer to gently roll-off whites in post etc

I'm only beginning to delve into the finer aspects of processing RED footage... but since everyone is saying you can dig even deeper into the shadows with Build 16, maybe the second option is indeed the best one. Of course, i'll be doing even more tests

I still don't have a definitive answer, so I'm throwing it out into the open. What viewing space are people using out there when setting exposure? Pros and cons with each one?

George

P.S. Also, my proxies look quite darker than what I'm seeing on the monitor when i shoot. Even when monitoring in REDSpace. Is that still an issue for everybody?

 

[John Tissavary]

I'm not a shooter, so my opinion is probably more from the perspective of grading Red footage, but...

I'd choose RAW for exposure and Redspace for video village. The only thing I would be concerned about when exposing is clipping at either end. But it's nice to show actors, director, producers, etc... the beautiful images resulting form the Redspace viewer lut.

As long as I'm satisfied with noise levels (or lack thereof) in shadows, and am not clipping shadows or highlights, I've got the best possible data for processing. Everything in between shadows and highlights can be manipulated to suit in the grading stage. Histogram biasing by exposure is a secondary, aesthetic choice (unless the full lighting dynamic cannot be captured on the sensor...).

cheers,

jt

 

[Uli Plank]

Well, it all depends on the contrast ratio in your scene. As long as it's less than the DR of the Red, you can shift your luminance values wherever you like.

But if it's high, you need to expose to the right, as close as possible, or you'll get more noise than necessary. You may even want to blow small, very strong highlights (like reflections on metal) to save the rest of your scene.

For this reason I'd like to ask a second time: Please, can we have the histogram working in raw, even when the image is set to REDSpace ?

The folks in video village don't care for the histogram, only for pictures. But as a cameraperson I'd like to see when my sensor is saturating. Or is this beyond the power of the processing in the camera?

 

[George A.]

Leaving the dynamic range of the scene aside, the question is: when shooting, is it a good idea to solidly expose to the right in the RAW VIEW, getting very very close to the right edge, even without clipping anything on the sensor?

True, the whites will be ok in the raw file. However, there is still the processing stage to enter the equation. Since you are barely under overexposure in the raw file, can you keep the highlights unclipped throughout the entire chain of postproduction? If yes, then perfect - I would ETTR all the time based on the RAW VIEW.

If not, then it's better to expose based on REDSpace, and let it act as a one-stop buffer to protect the highlights (or to have enough room to roll them off more gently in post).

I still believe ETTR-ing all the way to the edge of the histogram (if possible) gives the best results on RED, as far as the overall image is concerned. However, I don't want to introduce clipping problems further down the road, despite the whites being protected in the raw file (protected, but too close to the right edge).

 

[Nate Clapp]

also- I have noticed that Redspace looks good on onboard monitor- but HDSDI sent to panasonic 17" looks clipped. Set camera for Rec 709- and panasonic monitor looks good. I guess that makes sense- that is that REC 709 sent to HD monitor would be the right choice- but I know clients are going to be worried when they are sent a slightly clipped overexposed shot to their client monitor, even though my little monitor looks good. Makes me think I may have to toggle over to rec 709 just before I roll so clients feel better. Has anyone else had this problem? If so- it would be nice to send redspace to monitors onboard and rec 709 down the pike for everyone else. Seems like redspace was made to fix low luminance on onboard, but now it has created opposite problem on other monitors. Or maybe I have totally misunderstood what's going on. if so, please enlighten me.

 

[Tim Sutherland]

What would be nice is to have a color space for onboard viewing (EVF and RED LCD) as well as histogram, and a second color space selectable for the preview, 720p, and HDMI viewing. That way you see your RAW or REDSpace histogram and view, while the HD monitors get REC 709, the best for them.

 

[Gunleik Groven]

Red Space is just a way of faking some extra headroom in the brighter areas on the RED. It's kinda adding a harder S-curve, thus protecting your highlights and still making your blacks look black...

It's a good plan if you're usually setting up your exposures too high based on the other preview luts, wb/asa settings etc.

 

[Antoine Baumann]

Personnaly I always let the camera on raw viewing and I "decalibrate" the director/client monitor by pushing the chroma and a bit of the contrast and everybody is happy. (I still would love to have "edge highlight" on red lcd but not on red evf and not on hd-sdi out).
When exposing looking to the raw I always let a bit of headroom with the highlight to be sure to "keep the highlights unclipped throughout the entire chain of postproduction", of course "you may want to blow small, very strong highlights (like reflections on metal) to save the rest of your scene".

ciao,
antoine.

 

[Tim Sutherland]

That's what we did on set too, I had to pull the director's monitors off calibration and just let the dp know that he should come up to the camera 8.4 or red lcd to see what the brightness really was if he was trying to get picky, although his monitor was pretty close.

 

[Stuart English]

HD-SDI and Panasonic Monitor

HD-SDI and Panasonic Monitor

also- I have noticed that Redspace looks good on onboard monitor- but HDSDI sent to panasonic 17" looks clipped. Set camera for Rec 709- and panasonic monitor looks good. I guess that makes sense- that is that REC 709 sent to HD monitor would be the right choice- but I know clients are going to be worried when they are sent a slightly clipped overexposed shot to their client monitor, even though my little monitor looks good. Makes me think I may have to toggle over to rec 709 just before I roll so clients feel better. Has anyone else had this problem? If so- it would be nice to send redspace to monitors onboard and rec 709 down the pike for everyone else. Seems like redspace was made to fix low luminance on onboard, but now it has created opposite problem on other monitors. Or maybe I have totally misunderstood what's going on. if so, please enlighten me.

It shouldn't look clipped (we test against Panasonic) So check your monitor levels against the internal test signals from the RED-ONE and see if that looks clipped too.. if so, your monitor probably has an issue.

 

[Rocco Schult]

For this reason I'd like to ask a second time: Please, can we have the histogram working in raw, even when the image is set to REDSpace ?

The folks in video village don't care for the histogram, only for pictures. But as a cameraperson I'd like to see when my sensor is saturating. Or is this beyond the power of the processing in the camera?

I believe so, yes. There are limits. Thats why scaling, color space etc. needs to be same - I guess the histogram measurement works after processing, so it depends on it. Maybe we will be surprised sometime because they manage to vice versa it.

 

[Nate Clapp]

I thought I checked- but I will again. So just to clarify- in redspace output picture should look good & the same in both onboard and Panasonic monitor at same time?
I will investigate further....

 

[Nate Clapp]

OK I humbly stand corrected- I put my Panasonic 8.4 up-it indeed looked like onboard monitor, matching redspace. I then plugged in my 17 inch and it looked hot and clipped. What the??? Anyway- reset gamma to "Normal" in 17 inch (where it should have been to begin with) and bingo problem solved. I feel much better about redspace now. Whew! Thanks for Stewart.