Where's my over brights?

[Bruce Findleton]

Strange going-ons with AspectHD. I'm using the latest build (90) and when I look at my clips in a Cineform project my over brights are getting clipped. The pic on the left is a frame from a regular Adobe project. The same frame on the right is from the Cineform project.

I've set Maximum Bit Depth in Video Rendering, I've got both Use HD Colorspace and Use videosystems RGB checked in the playback settings. Is there something else that I'm missing?

Bruce

[David Newman]

Likely nothing lost. The scopes prior to CS3 couldn't show over brights, nor did they tell us they now could. We refresh the scopes with cgRGB, as that was all it used to support, and cgRGB will not show above 100%. We will consider that upgrade. Note: It still seems the RGB scopes are 100% limited.

However, your highlight are not lost, as you can put on a color corrector to pull the highlights into range.

P.S. all this is much easier in Prospect HD/2K which natively supports 32-bit float for much better highlight preservation.

[Bruce Findleton]

I'll usually toss a ProcAmp effect on it and lower the contrast until I've recovered as much as I could but this looks like it's actually lost the data. Are you saying that it's just a scopes issues. This could get messy.

And, yes, I'm biting the bullet and upgrading to Prospect HD next week.

[Bruce Findleton]

I'll repeat my last: Is this just a scopes issue or have the values actually been clipped?

[David Newman]

Just a scopes issue.

[Pete Bauer]

Bruce, might be possible to doublecheck by exporting frame grabs of the same frame using native HDV and CF AVI, then comparing RGB and/or luma levels in Photoshop? If a super white area has the same RGB values whether done in native HDV or with a CF AVI, you can feel more assured that no clipping is happening.

[Bruce Findleton]

Well, things are getting interesting. I tried a variation of your suggestion.

First I exported the same frame from the same source (Cineform .avi) out of an Adobe project (I'll call this native) and an Aspect project. Each had a ProcAmp effect applied with Contrast set to 90. In Photoshop I combined them into one image and set the upper layer to the Difference blend mode. There were noticeable differences.

Next I exported the same frames with the effects turned off and diff'ed those and still noticeable differences appeared.

Then I diff'd the two native images and compared it to the diff'ed Aspect images. Very nearly identical but the Aspect images had greater differences.

Finally (I can hear your sigh of relief) I exported the native image with the ProcAmp removed but a unadjusted Levels effect added. This dropped it into RGB space; you can see noticeable color changes when you turn the effect on and off.

This one was almost identical to the Aspect/no effects image while it had significant color changes compared to the native/no effects image.

Since adding the RGB effect to the native clip makes it look much more like the Aspect clip with no effects I'm thinking that I am in fact missing my over brights in the Aspect project.

Suggestions and comments about what's going on would be welcome.

[David Newman]

Why not just put a CineForm color corrector on it, and reduce the brightnessto see that there is highlight information still present. All this messing around with RGB is just confusing. In Prospect HD we use float on the scopea, while they still display in RGB, you can see the highlight be extracted from 100%+ as you reduce the brightness or contrast.

[Bruce Findleton]

Brightness brings down the entire image. The ProcAmp effect works in YUV and when you bring down the contrast it leaves the blacks where they are. Kinda nice that way.

I'll be Prospect enabled next week so the issue will presumably be moot by then. Thanks for the assist.