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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 :)

Whats the best colour space to export for DPX

S

simonpeterarnold

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Just asking what everyone here is suggesting to use for colourspace wise for export of DPX. We have used rec709 for the last 3 and it has been of but I am sure we should be using one with more depth. We tried Redlog but our graders seemed unimpressed with the results. Also the camera gamma is set to CameraRGB is this correct or should it be rec709 as well. How do I tell which one to use.
 
simonpeterarnold said:
Just asking what everyone here is suggesting to use for colourspace wise for export of DPX. We have used rec709 for the last 3 and it has been of but I am sure we should be using one with more depth. We tried Redlog but our graders seemed unimpressed with the results. Also the camera gamma is set to CameraRGB is this correct or should it be rec709 as well. How do I tell which one to use.
Click to expand...

If they "seem unimpressed with the results" then the chances are pretty good that they don't know what it is, don't understand what log coding does, and don't know how to properly set it up.

Using any video gamma color space to create 10 bit DPX files is a waste of bits, and an improper use of the available data. Not to mention that DPX files are usually assumed (at least in the world of post production) to be log encoded in the first place. If you're creating 10 bit DPX files from 12 bit R3d data, you should be using a log encoded color space - Redlog, or in some cases, PD685.
 
mmost said:
If they "seem unimpressed with the results" then the chances are pretty good that they don't know what it is, don't understand what log coding does, and don't know how to properly set it up.

Using any video gamma color space to create 10 bit DPX files is a waste of bits, and an improper use of the available data. Not to mention that DPX files are usually assumed (at least in the world of post production) to be log encoded in the first place. If you're creating 10 bit DPX files from 12 bit R3d data, you should be using a log encoded color space - Redlog, or in some cases, PD685.
Click to expand...

He's completely right. Your grader is not that experienced or more likely an editor that grades, kind of a guy?

edit: the purpose for DPX is to create a "negative" for you to grade from. Therefor you want to try to "keep" as much info as possible, for your session. That's what it's all about.
 
Can we separate out discussion of the gamma curve used from the colour space used? It's very confusing to refer to a gamma curve as a colour space!

The REC709 gamma curve is totally appropriate to use with a 10bit DPX. It's not the optimum curve for a 12bit to 10bit conversion (REDLOG is that optimum curve) but a REC709 gamma is not bad by any means. The only "curve" that is bad is linear light as you basically throw two stops away. Ok, they're the darkest two stops, but it does make a difference.

For colour space - cameraRGB or REDspace are totally appropriate.

The important thing is just to ensure the exposure and ISO are set so as to avoid any highlight clipping from the processing.

Graeme
 
Graeme Nattress said:
Can we separate out discussion of the gamma curve used from the colour space used? It's very confusing to refer to a gamma curve as a colour space!

The REC709 gamma curve is totally appropriate to use with a 10bit DPX. It's not the optimum curve for a 12bit to 10bit conversion (REDLOG is that optimum curve) but a REC709 gamma is not bad by any means. The only "curve" that is bad is linear light as you basically throw two stops away. Ok, they're the darkest two stops, but it does make a difference.

For colour space - cameraRGB or REDspace are totally appropriate.

The important thing is just to ensure the exposure and ISO are set so as to avoid any highlight clipping from the processing.

Graeme
Click to expand...

Thanks, for the advice. With regards to ISO are there any guidelines for setting this as so far I have left them as the are from the R3D files. Just for the record I am not a grader but the operational end of getting the files converted to be graded in Baselight so my knowledge of colourspace is limited but I have been asked to set up the workflow for our company.
 
Set ISO to 320. Adjust exposure to ensure no clipping. You may not need to adjust the exposure so check the histograms.

Graeme
 
I get extremely lost understanding the whole log/linear thing, I come from simply capturing into avid and editing and color correcting there.

Now that we have 2 red cameras, and have possible film out projects coming up, I'm trying to learn about log as it obviously is a better way to go for film out.

I have no idea where to start to understand log, like when I switch the gamma to redlog in redcine, everything goes all pasty, if one is chosing redlog in redcine are you meant to then adjust curves to make it look correct, or is there something you are meant to do to your monitors to adjust for log grading?

It's obvious I know nothing about this subject, is there anyone that understands how this all works that would be willing to give me some consultation over the ph, or if possible on the board here, if so pls PM me or let me know here, I would be willing to pay a fee for the time if need be.

Thanks
Stricko
 
I have from 3 post companies worked on getting DPX from REDCode. What was found by them is that the gamma curve in REDLog is slightly to high so they recommend to bring it down in exposure setting with approx. -0.5.

Now I'm not an expert but that worked fine for us.

I use camera RGB and REDLog 2K DPX with an adjustment of -0.5 in exposure for each clip and Lanczos as filter setting. Each post house has asked me not to apply and NR, they all felt it was to strong and rather do it themselves, if necessary. This has worked brilliantly for me, even to make a film print out of. After it of course has been graded in a CC suite, such as Baselight or Lustre etc.

All this is of course so we could preserve as much for the actual grading in the suite and not before.
 
The 0.4 stop buffer is no longer there with B16, so you can see where you clip more accurately in camera.

Graeme
 
What I'm starting to gather is if you are coming out of redcine for say AVID Composer, then doing a 1st pass correction and rendering out linear is the go, and if you are going to take your files to a DI House for grading, then chosing Log and not adjusting things to much in redcine is the go.

One more question, when someone is grading footage with say a log dpx file, does the programme display the picture all pasty, like it looks in redcine when one choses redlog for example, and the colorist just adjusts colors to getting it looking good, or do those programmes understand log and before they get grading it already looks more like rec709 for example looks like in redcine, not sure if I'm making any sense, just trying to understand how this all works.

Any help appreciated.

Thanks
Stricko
 
Depends on the colorist and the final output

for SD/HD they view on a Grade1 ref monitor and grade to that.

Going to film is different and you grade with a Viewing LUT thats dependent on the stock your film outing to and possibly a 3d LUT from a calibration company for your projector/monitor.

Actually there is a tonne more than that to film but thats the jist.

s
 
stricko108 said:
One more question, when someone is grading footage with say a log dpx file, does the programme display the picture all pasty, like it looks in redcine when one choses redlog for example, and the colorist just adjusts colors to getting it looking good, or do those programmes understand log and before they get grading it already looks more like rec709 for example looks like in redcine, not sure if I'm making any sense, just trying to understand how this all works.
Click to expand...

Log coded images are not meant to be viewed. They're created as containers for information that you then de-log for proper viewing and color correction. Basically, they are meant to be an intermediate file. They are not intended to be color corrected directly, although I suppose with enough gamma correction, you could do that - but a number of values will still not be where they should be.
 
flameop said:
how many colorists apply a LUT first though.. and how many just bring the blacks down n whites up then crack on :-/
Click to expand...

Depends on the Lut. All the times I've graded has been with print film Lut's and the result is simply amazing.
 
flameop said:
how many colorists apply a LUT first though.. and how many just bring the blacks down n whites up then crack on :-/
Click to expand...

Yikes. I hope not many. There are colorists out there that don't necessarily have a great deal of experience outside the telecine/broadcast market. If you're going for filmout or DCDM without someone experienced in delivering those media, then to me it's like bringing your car to a bicycle shop for repairs.

cheers,

jt
 
Thanks guys, I'm starting to understand how this works now,
for HD release I'll stick with redspace or rec709.
If and when I need to goto film, I'll hire a house that knows there stuff.

THanks again

Stricko
 
weirdcrew said:
Each post house has asked me not to apply and NR, they all felt it was to strong and rather do it themselves, if necessary. This has worked brilliantly for me, even to make a film print out of. After it of course has been graded in a CC suite, such as Baselight or Lustre etc.
Click to expand...

IMHO, the catch there is that unless you're in a 4k session when you apply NR you're getting (noticeably) inferior noise management. I'm guessing nearly 1/2 stop improvement in the noise floor when debayering at 4k vs. 2k.

I would, however, love to see adjustable NR back in Scratch/Redcine. It's not enough to have it just go on/off - amount of application control is essential.

I realize everyone's got their fave colorists and tools, but it should not be underestimated how beneficial it is to have the RAW debayer at the end of the processing chain. I avoid debayering prior to CC, so until other systems can including R3D native support I won't grade on anything but Scratch. I adore Scratch, and yet I'm also looking forward to the SDK so Baselight and Nucoda (and a ton of other tools) can support Red projects.


cheers,
jt
 
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