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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?

S

Stu Maschwitz

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Is it possible to use a "RED Log" or "PD Log 685" curve in the camera while shooting? So as to preview log rather than Rec709?

-Stu
 
Stu,
At NAB I seem to remember the team saying you could pull an image into Redcine build a LUT and load it back into the camera. My guess it will be a while though before this is potentially implemented.
 
So in the meantime we have only one hard-coded preview color space?

I am preparing a blog post about the potential treacherousness of shooting with a Rec709 preview for eventual filmout.

-Stu
 
ProLost said:
Is it possible to use a "RED Log" or "PD Log 685" curve in the camera while shooting? So as to preview log rather than Rec709?

-Stu
Click to expand...

Direct previewing of log is not very useful as it will appear very low-contrast. Hence, some sort of log->linear operation may be in order here. In addition, if you shoot using Log/gamma and then linearize later, you would have lost a lot of linear light detail which would be helpful in linear-domain tone-mapping.

In the normalized image intensity range, log (DPX Log; don't know what exactly is the formula for PD/Red Log) and Rec 709 gamma of 0.45 might behave similarly. Please notice that I am talking about "behavior" of response and not the actual pixel intensity vis-a-vis log vs. gamma.

I have to check back on this fact. But top my head would be the behavior of the responses might be similar, even if actual intensity values are different. Hence, even if you directly preview them (without linearizing them), they might exhibit similar pattern.
 
Other previewing modes will come post build 15.
However, improvements to the current viewing modes will
be in build 15.

PDlog685 wouldn't be so great for metering because it's
constrained so much but would make external print emulation
previewing viable.

REDlog would be ideal but you'd have to build a your external luts off REDlog.
 
Deanan said:
REDlog would be ideal but you'd have to build a your external luts off REDlog.
Click to expand...

If I understand you correctly that you are saying that one applies lut mapping on the RedLog, instead of linear data, then you would have lost some linear light detail, which might be helpful in certain circumstances.
 
Joofa said:
Direct previewing of log is not very useful as it will appear very low-contrast.
Click to expand...

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.
 
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
 
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.
Click to expand...

Sure, you are right. I think those systems will do a high-contrast mapping of the low-contrast log data, similar to what I talk about in the following thread:

http://www.reduser.net/forum/showthread.php?p=157670#post157670

So basically, you fit a high-contrast curve to the low-contrast data, either in functional form, or through the lut, which implements the functional form. Gamma of 0.6 on film negative is low contrast. In the post I mention high-contrast gammas of 2.5 - 4.0 on the print film, and end-to-end system gamma of 1.8, which is also high-contrast.
 
ProLost said:
Based on the published information about Genesis Panalog (the tell you where back, 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
Click to expand...

I'd love for you to do that Stu - bring it!
 
Thanks Mike for saying it better than I did.

Joofa, going from 12 linear to 10 linear out the HD-SDI would not be a good thing and would result in a loss of DR.

Stu, do you mean a REDlog to Linear LUT?
 
Indeed, that's what I would like to see—and its inverse, i.e the transfer function used in RED Alert to go from linear to RED Log.

-Stu
 
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