Pixel Dropouts, Why?

[Tim Paynter]

Intermittent problem with pixel dropouts. I feel like giving up as a videographer because this happen sometimes and then sometimes not. Please check around 3.40 and you will see the dropouts on Manuel's tunic.

Could this be dust? Using Adobe Premiere 5.5, shot at 60 p, maybe that is one problem, but had the same problem at 30 p on another video.

Need help or need to figure out something else to do, but I can't turn in work like this, and I never know when it will happen and when not.

Shot PD 170 DV mode. Captured with HVR M10u

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[Tim Paynter]

Actually, that should be around 3.43, lots of little black dots popping in and out... just drives me nuts!

[Gregory Gesch]

Hi Tim. Sorry I'm not a Techie but some more information may help someone get a handle on what's going on. When is this occurring? Is it on the original footage, is it happening when you are viewing it in Premiere or only when you render it out? If all is clear until the render what are your render settings? Your highlights are very odd as well, instead of blowing out to white they are becoming black? Are you using any Effects on the clips, if so which? The only time I have personally seen something like this was when I was pushing some colour correction effects too far but, hopefully, someone else may have other ideas.

[Tim Paynter]

I applied the spotlight effect because, despite having a top light, my subject was still dark.

I didn't spot the dropouts until I rendered, then went back into Adobe to check, and you can see them if you look really hard. So in rendering they become significantly worse, or at least you can see them more.

The dropouts seem get progressively worse, especially after the short break. It was all from one clip, so not sure why this is happening. I have done several videos with no problems before with this cam, and then all of a sudden, the problem is back.

I really appreciate the help, over 100 people have viewed this and you are the only one to respond, it can't be that rare, is it?

[Battle Vaughan]

My Guess: dropouts from dirty tape heads or defective tape (maybe tape that has been used several times) on the sony deck you mention; and the effects are emphasized by the post processing you are doing, the image looks like it has been boosted in brightness and/or contrast a lot and has the shadows raised quite a lot. this would make the dropouts --which are black no matter what --- stand out from the raised dark areas.

[Gregory Gesch]

What Battle says makes good sense. Am I correct in thinking that the first sequence of him is without the Spotlight effect? If so, is the rest of the shot of the same quality without the effect or did the lighting and/or exposure change? My suspicion is that it's the spotlight which may be causing most of the problem, but without seeing some raw footage it's difficult to give you any concrete advice as to an alternative. Perhaps you could post a small section of clean raw footage for me/us to have a look at and be able to make some suggestions? If so do you also have After Effects?

[Battle Vaughan]

The real issue is what to do about it. The dropouts stand out against the uniform, which appears to be the only place they are visible.

You might just bring down your lower quarter tones some to lessen the contrast with the spots and see if that's enough. If not, you could make a duplicate track as an overlay, matte out just the uniform on the dupe track and apply a little gaussian blur to the matte area == not enough to blur the image unacceptably, but enough to soften the spots. Keep the blur off his face and the medals and it won't be so noticeable.

[Tim Paynter]

Thanks for the responses. I finally cut out the bad video and inserted new captured video. I think the culprit was the spotlight I put on in post.

Here is the final piece with some changes. Soon enough, I hope to afford better equipment, but one thing is sure, I better have dough to upgrade the editing side if I upgrade the video cam.

Again thanks for your help.

Tim

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[Juris Lielpeteris]

Such a defect could occur inadvertently using some effects like chroma key

[Battle Vaughan]

Here's what my suggested fix(s) look like.

One jpg is the before and after a simple curve adjustment to the blacks.

Second jpg shows what the overlay track with the black adjustment, blur and matte looks like. Everywhere it's black, outside the mask, the track below it shows through. (obviously, you make the same adjustment to the curves on both tracks so the hat, etc, are consistent with the level of the rest of the quartertones.)

The system wouldn't let me upload a video clip for some reason, so the last jpg is a still frame from the output. Obviously you can fine tune all the perameters to your liking, but here's one idea of how to repair this......

[Tim Paynter]

Thanks for the tip. I tried my hand at masks a while back but got frustrated and threw in the towel. That might be the solution if I have the problem again.

I also tried to chroma key this just for the fun of it but thought I had undone all of my changes and gone back to the original. By the time I got to the rendering, I was thousands of changes beyond the chroma phase, so could not have gone back to undo those changes. If it was playing around with chroma that caused this I didn't realize it until way to late.

I have a lot to learn about this. It helps to figure out what went wrong so I can avoid this in the future.

Thanks for the tips, guys.

Tim

[Jeff Pulera]

Hi Tim,

The new clip looks much better, I would blame the lighting effect and encoding compression for the black artifacts in the uniform. Worked with DV for many years, and DV tape dropouts are much larger square blocks due to the way the compression matrix works. Not the little specks your clip showed.

Thanks

[Tim Paynter]

More dropouts, especially during the river rafting sequence. Different camera....

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