TOPIC:

I have HLG/rec 2020 clips on a Wide Gamut timeline. Everything looks fine.

I have some overlays I would like to use... dust/sparks/flares/etc. These are shot on a black background. The usual procedure is to place them over a clip and set blend mode to screen. Works as intended on a SD/709 timeline.

On the wide gamut timeline, things get strange. The overlay clip looks fine on its own. Once switched to a "screen" mode, the colors are all off. It's like a grayish tint over everything. The waveform display show everything clamped down/clipped around 50IRE (actual value changes depending on the overlay clip)

I've attached an image of the RGB parade to illustrate.

I have tried:
Changing exposure values - waveform is still clamped to the upper limit
Color space override - no effect
HDR tools/Color Comfort - will brighten colors in "normal" mode, but no effect on "screen" mode

Any ideas how to work around this?

Would you mind posting a still image from the base layer video and a still image for the overlay effect clip (PNG or TIFF would be good)?

How about trying ADD as a composite option instead of SCREEN? I've come across situations where a different choice produces the desired effect but without odd complications, like the clipping going on as evidenced in the last pane.

Here is a selection of screen grabs showing the clips, scopes, and settings.

VTC wrote:

How about trying ADD as a composite option instead of SCREEN? I've come across situations where a different choice produces the desired effect but without odd complications, like the clipping going on as evidenced in the last pane.

Interesting. I had run through all the blend options and none produced the effect that "screen" is supposed to. However, I just tried it with "color conform" turned on for the overlay and it seems to work for _some_ clips.


I should also point out that the clip I posted in my previous post was for example only. I was just trying out random overlays to see if I could get one to work. Also, I intentionally left the overlay to a standard aspect ratio to better illustrate the problem.

jrm wrote:

Here is a selection of screen grabs showing the clips, scopes, and settings.

It would be helpful to get actual stills of each actual clip that is producing the problem (you know, something that could be used for some testing). That's why I asked. It could be a color space issue, or something else. It would be helpful to know your type of CPU, macOS version, as well as FCP version. I doubt there are mind-readers here on the forum...

DaveM wrote:

jrm wrote:

Here is a selection of screen grabs showing the clips, scopes, and settings.

It would be helpful to get actual stills of each actual clip that is producing the problem (you know, something that could be used for some testing). That's why I asked. It could be a color space issue, or something else. It would be helpful to know your type of CPU, macOS version, as well as FCP version. I doubt there are mind-readers here on the forum...

I misunderstood what was meant by stills. Figured a screen grab was what was meant.

So a simple save current frame output? I I’ll do that when I get home.

not at home to see actual version right now, but…
Mac Studio m1 ultra
latest/current OS
latest/current fpx

Here are the "stills" - one of the underlying video, and one of the overlay.

Not sure these frame exports will help as they don't illustrate the problem. When this overlay image is brought back into FCP, it behaves properly. Blend mode can be set to "screen" and it will work as intended.

Learning this, I placed the overlay video clip in a wide gamut timeline and export as a 10 bit HDR clip. I figured this is essentially what the frame export process was doing. However, only the still image worked when brought back in. The video file is recognized as HDR, but still doesn't "screen" blend properly on the wide gamut timeline.



Clip would not attach to previous message. It is attached here.

Note that the underlying clip was too large for upload. I had to bring it into PS and re-save as a PNG to get file size down.

jrm wrote:

Clip would not attach to previous message. It is attached here.

Note that the underlying clip was too large for upload. I had to bring it into PS and re-save as a PNG to get file size down.

Hmm, I would have thought you could use "Share" and simply export the current frame in the timeline. Anyway, the still for the clip you posted is using the sRGB color space, so my test results may not be indicative of what you're seeing in FCP.

I converted the clip image into Rec. 2020 colorspace and imported it into Affinity Photo, along with the overlay image. Using screen blend mode, things appear to look as one would expect:


I imported the overlay and my converted version of the clip into FCP. In an HLG timeline (in a wide gamut Library), the screen blend mode yielded gray, as you mentioned. The add blend mode gave me a similar result to screen mode in Affnity Photo (or what you'd expect with screen blend mode in FCP, sort of):


I'm using FCP 10.6.5, so I don't have the "color conform" feature. I don't know if using the sRGB still of the clip you posted affected things, or whether my simple color space conversion affected things, either. Strange...

My initial thought was that it might help to do what you did (convert the overlay to HDR and export then re-import it). You might want to check out some of the generators or effects bundled with FCP to see if they might work for you, or at least to see if they behave properly (or as you'd expect when using the screen blend mode).

DaveM wrote:

Hmm, I would have thought you could use "Share" and simply export the current frame in the timeline.

That's exactly what I did for both overlay and clip. The problem is that the clip file was over 30MB and too large to upload to this forum. I brought it into PS to reduce the file size.

Anyway, the still for the clip you posted is using the sRGB color space, so my test results may not be indicative of what you're seeing in FCP.

I converted the clip image into Rec. 2020 colorspace and imported it into Affinity Photo, along with the overlay image. Using screen blend mode, things appear to look as one would expect:

I imported the overlay and my converted version of the clip into FCP. In an HLG timeline (in a wide gamut Library), the screen blend mode yielded gray, as you mentioned. The add blend mode gave me a similar result to screen mode in Affnity Photo (or what you'd expect in FCP):

I'm using FCP 10.6.5, so I don't have the "color conform" feature. I don't know if using the sRGB still of the clip you posted affected things, or whether my simple color space conversion affected things, either. Strange...

What's especially odd to me is how the clip behaves differently than the video file it came from.

The still - original frame export and smaller PS version that was uploaded here - behaves properly in FC. Screen mode works as expected.

The video - both the original SD version and one exported as a 10-bit HDR from a wide gamut timeline - exhibits the problem.

One would think that the frame export and video export would behave the same, but they don't.

FYI - color conform seems to be nothing but an automatic/built-in version of HDR Tools. Same conversion options on both, its just that CC is always there and has an "automatic" function. Regardless, in this particular case, CC, HDR Tool, and color space override provide no help.


I guess "add" is the solution here -but it still bugs me why screen blend doesn't work.

jrm wrote:

That's exactly what I did for both overlay and clip. The problem is that the clip file was over 30MB and too large to upload to this forum. I brought it into PS to reduce the file size.
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I guess "add" is the solution here -but it still bugs me why screen blend doesn't work.

Aha, I understand. Sorry about that. PNG or TIFF stills from larger frame sizes can easily be over ~7 MB in size (the limit for attachments here, it seems).

Me too. I'm a bit confused about the behavior, though I don't have the source media you have. Is there an alpha channel in the overlay video? I'm grasping at straws, a bit.

Add blend mode does slightly change some of the mid-range colors, it seems, but if it's a decent workaround that's cool. Maybe someone else reading this thread will have a better idea about what's happening...

No alpha channels involved.