Levels: highlight cut off

[anton_foy]

Hello,

I do not understand why is this:

Levels(0, 1, 65280, 0, 65280, coring=false, dither=false)

is cutting off my highlights?

http://www.imagebam.com/image/7cf4ca1355130247

If I use this line

Levels(0, 1, 65280, 0, 235*256, coring=false, dither=false)

it keeps the highlight intact
http://www.imagebam.com/image/6309cc1355130248
but do I really need to do this to not loose my highlight information? I want to keep as much information as possible.

Thanks!

[poisondeathray]

It's cut off by the limited range RGB conversion. The Y values are still there , you just don't "see" them in an RGB image

235*256 = 60160

In the 1st image, for 16bit values you have bright cloud values in the Y=60160-65280 range. (This is analogous to Y 235-255 in 8bit values when converted to RGB for display using limited range, they get clipped by the RGB conversion)

The 2nd example with levels depresses the output high to 60160 (analgous to 235 in 8bit) before the RGB conversion, so those values are not clipped, but the whole waveform is compressed from the top, so entire image is darker. This applies range compression from the top (squishes the waveform)

[anton_foy]

@poisondeathray
Thanks so what would you suggest would be the best option to keep the info in the image as much as possible?

[Cary Knoop]

Originally Posted by anton_foy

@poisondeathray
Thanks so what would you suggest would be the best option to keep the info in the image as much as possible?

Use float32 for processing.

But the more interesting question is why do you think you need to use the Levels function in the first place?

Also, out of curiosity what lens are you using?

[poisondeathray]

Originally Posted by anton_foy

@poisondeathray
Thanks so what would you suggest would be the best option to keep the info in the image as much as possible?

Depends on what you want to do with it, and/ or how it's going to be viewed

If you're keeping it as limited range video, then definitely bring the "superbrights" down. But just compressing the highlights darkens the image. But maybe that's the look you're going for. Maybe not. Maybe you want to bring midtones up a bit . You have more control in other programs such as resolve or NLE's

[anton_foy]

Originally Posted by Cary Knoop

Use float32 for processing.

But the more interesting question is why do you think you need to use the Levels function in the first place?

Also, out of curiosity what lens are you using?

Thanks, I will try to do the processing in 32 bit float (although I would suspect my computer cannot handle it until I upgrade as even in 16 bit my export crashes due to "out of memory").

Regarding levels, if I do not use it at all I get blown out highlights and the only solution I could come up with was this:
Levels(0, 1, 65280, 0, 235*256, coring=false, dither=false)

The lens is a Tamron 10-24mm f/3.5-4.5. Not so sharp but nice for the wide angles. In this test clip the focus is off tho.

[anton_foy]

Originally Posted by poisondeathray

Depends on what you want to do with it, and/ or how it's going to be viewed

If you're keeping it as limited range video, then definitely bring the "superbrights" down. But just compressing the highlights darkens the image. But maybe that's the look you're going for. Maybe not. Maybe you want to bring midtones up a bit . You have more control in other programs such as resolve or NLE's

Thanks, the look does not matter too much (it is in Slog2) since I will be color grading it in Resolve and I want to keep as much info as possible when it gets imported into that. But if I keep it as limited range video it will have "unused" margins (16*256 steps up for black and 20*256 steps down for white) right?

[Cary Knoop]

Originally Posted by anton_foy

Regarding levels, if I do not use it at all I get blown out highlights and the only solution I could come up with was this:
Levels(0, 1, 65280, 0, 235*256, coring=false, dither=false)

That's odd.

I can take a look at things if you provide an out of camera clip compared to your results after processing.

Originally Posted by anton_foy

The lens is a Tamron 10-24mm f/3.5-4.5. Not so sharp but nice for the wide angles. In this test clip the focus is off tho.

Quite a heavy chromatic aberration at the edges.

[anton_foy]

Originally Posted by Cary Knoop

That's odd.

I can take a look at things if you provide an out of camera clip compared to your results after processing.


Quite a heavy chromatic aberration at the edges.

Thanks! I did another test and found out that when I import the frames in Photoshop the highlights are lost / blown out but I found that when I import the processed clip into Davinci Resolve and change levels from "auto" to "full" under "Clip attributes" the highlights are back. So Resolve interprets the clip incorrectly and I have to manually set this on each clip I import. Well that solved it. No more need to use Levels.

Yes it is quite some chromatic aberration on this one but I like the lens in some situations

Here are the clips:
https://we.tl/t-nWFpkdzzCT

[Cary Knoop]

Originally Posted by anton_foy

So Resolve interprets the clip incorrectly and I have to manually set this on each clip I import.

Not necessarily.

Resolve loads video levels by placing the visible range between 0.0 and 1.0 float32.
If the clip has WTW, you can pull it in using highlight roll off, as Resolve never clips.

As a matter of fact Resolve interprets your sheep clip as full, not even the transients go out of range even when I interpret the clip under video levels, so I do not understand how you observe any clipping.

Assuming the clip was recorded Rec709 the video is underexposed and the temperature is a bit on the cold side.

The other clip is also full range and interpreted correctly by Resolve. This clip is overexposed, and you have blown out highlights that cannot be recovered.

Check the camera options because for Rec709 videos you should really use video levels.

[anton_foy]

@Cary Knoop

As a matter of fact Resolve interprets your sheep clip as full, not even the transients go out of range even when I interpret the clip under video levels, so I do not understand how you observe any clipping.

I meant the processed clip not the original ones. But good then I can just pull it back either way then.

[Cary Knoop]

Originally Posted by anton_foy

@Cary Knoop


I meant the processed clip not the original ones. But good then I can just pull it back either way then.

Unfortunately, there is really nothing to pull back on either clip.

[anton_foy]

Originally Posted by Cary Knoop

Unfortunately, there is really nothing to pull back on either clip.

I think you misunderstood. Did you watch the images I uploaded? In one of them the highlights are more blown out and the other is not as much. So when I switched to levels "full" in Clip Attributes in Resolve I did not have that problem anymore. So that is what I meant by "pull back".

[Cary Knoop]

Originally Posted by anton_foy

I think you misunderstood. Did you watch the images I uploaded? In one of them the highlights are more blown out and the other is not as much. So when I switched to levels "full" in Clip Attributes in Resolve I did not have that problem anymore. So that is what I meant by "pull back".

We seem to have a misunderstanding, the sheep clip is underexposed and there are no blown-out highlights while the test clip is overexposed, no processing will be able to recover those.

[anton_foy]

Originally Posted by Cary Knoop

We seem to have a misunderstanding, the sheep clip is underexposed and there are no blown-out highlights while the test clip is overexposed, no processing will be able to recover those.

Yes they are underexposed and overexposed, out of focus and not correct white balanced etc. hence "test clips". But I used them not to impress you but for the purpose to demonstrate my problem with "clipped highlight" (the castle clip anyway) that is caused by how Resolve displays the clip depending on if full, video or auto settings on levels. Now it is working and I am happy

[Cary Knoop]

You are missing the point, the point is that the test clip is clipped beyond repair:

https://www.dropbox.com/s/nhb2136xthuymze/clipped.jpg

It is not a full versus video levels issue.

[WorBry]

Also checked out the clips in Resolve and agree with Cary - the 'test' clip is full range and over-exposed i.e. when brought into Resolve at 'Full' data levels the highlights are clipped - there is no latitude for 'highlight pull-down'.

You could have a go at softening the margins of the clipped patches of sky with a qualifier mask, but I think I'd be more inclined to import the clip at 'Video' levels, darken it with a Layer Node and 'Multiply' composite blend ('opacity' = Key Output Gain around 0.30 to 0.35) and apply a Soft Clip with the Curves Tool (H.S around 39) to bring the clipped highlights just into range. Maybe add some Mid-Tone Detail and adjust Saturation to taste.

[anton_foy]

Originally Posted by Cary Knoop

You are missing the point, the point is that the test clip is clipped beyond repair:

https://www.dropbox.com/s/nhb2136xthuymze/clipped.jpg

It is not a full versus video levels issue.

...once again, I know it is clipped beyond repair, it is white totally in some places in the castle clip BUT that is NOT the point. Look at the first images I uploaded and compare them side by side. Then you will see that one is more blown out the other and that is the same exact frame, that was the POINT of this thread of how to process without clipping even more.
I could use a non blown out highlights to demonstrate the problem but that would not make much sense since there are not enough brights in the image.

http://www.imagebam.com/image/7cf4ca1355130247
http://www.imagebam.com/image/6309cc1355130248

[anton_foy]

Originally Posted by WorBry

Also checked out the clips in Resolve and agree with Cary - the 'test' clip is full range and over-exposed i.e. when brought into Resolve at 'Full' data levels the highlights are clipped - there is no latitude for 'highlight pull-down'.

You could have a go at softening the margins of the clipped patches of sky with a qualifier mask, but I think I'd be more inclined to import the clip at 'Video' levels, darken it with a Layer Node and 'Multiply' composite blend ('opacity' = Key Output Gain around 0.30 to 0.35) and apply a Soft Clip with the Curves Tool (H.S around 39) to bring the clipped highlights just into range. Maybe add some Mid-Tone Detail and adjust Saturation to taste.

Thanks yes as I explained in my earlier post I am not interested in highlight "pull down" or "roll off". This is just a test clip showing the difference that was bothering me and (see previous or first post for image comparison) between different settings (levels) on the same frame. The solution for me was to remove the levels line in my avs-script and use "full" levels in Resolve and the blown out highlights were no more double blown out.

Poisondeathray

It's cut off by the limited range RGB conversion. The Y values are still there , you just don't "see" them in an RGB image

he replied this and that was the answer, I just did not know how to make it visible again until now.

[Cary Knoop]

And again, I would update the camera settings to use video levels for Rec709 instead of full levels.