Color Aliasing/Pixelating/Bending?

Explorer ,
Jun 10, 2021 Jun 10, 2021

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Hey there Adobies,

 

So, I color corrected and graded my iphone 6s footage in premiere pro and then there was a color aliasing/pixelation/bending (please tell me the correct term before I keep on making a fool of myself :D) in the bottom left of the footage. Could you tell me why this is the case? Is it because the color range on Iphone 6s isn't good?Capture.PNG

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Adobe Community Professional ,
Jun 10, 2021 Jun 10, 2021

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maybe try to add a slight Gaussian Blur

did you try to transcode to constant frame rate using Hanbrake?

https://handbrake.fr/

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Explorer ,
Jun 11, 2021 Jun 11, 2021

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Do I have to do that with every footage? Handbraking it? So, the color bending happened because of NON constant frame rate?

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Adobe Community Professional ,
Jun 10, 2021 Jun 10, 2021

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Looking at the image, in several places you clearly have light spaces where there's a band around it. Which shows there is clipping going on in the original clip with the color balance being off. So channels are clipping at different levels.

 

I would guess you need to get better control over the exposure of that and this can be tricky with some phones. But auto-exposure can be a killer for video work.

 

Neil

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Explorer ,
Jun 11, 2021 Jun 11, 2021

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So, this means NO auto exposure?

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Explorer ,
Jun 11, 2021 Jun 11, 2021

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Also, the so called clipping happened because in the "luma vs saturation" curve I brought down the end the top down so that the blacks and white won't be affected by the color grading. The video clip itself had no clipping whatsoever. I still don't understand why that is the case though? Why when I put it down in the "luma vs saturation" curve, it looks like it's clipping?

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Adobe Community Professional ,
Jun 11, 2021 Jun 11, 2021

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You used too much of the Luma v Sat ... and one other odd thing, with Luma v Sat and Sat v Sat, never EVER take any spot above the starting mid line ... only drop parts of the curve.

 

Blacks and whites won't be affected notably by color corrections/changes because there's very little color at the ends of the range already. I do tend to use the luma v sat to lower color content in deep shadows and hightlights myself, but again, only pull down, and in a gradual curve.

 

Auto-exposure and auto-color balance are a total drag in video post production. Turn your head, the exposure or white balance can and will change. Ditto if someone walks between the light and the image, leaving a shadow across the wall behind you. Or clouds passing over sun outside even though you're inside.

 

Correcting for that is a right pain.

 

Neil

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Explorer ,
Jun 13, 2021 Jun 13, 2021

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Thank you so much for this!

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Adobe Employee ,
Jun 11, 2021 Jun 11, 2021

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Good morning winster,

Thanks for writing in today with your issue. I'm glad you are mindful of trying to correct such errors, however, in this case, you don't have a lot of options. You may have to live with these hot spots because there is no color information left in those areas. As Neil suggests, you can go less aggressively with some of your Lumetri settings.

 

Next time you shoot, you have a chance to fix these things. I would try and correct the issue before shooting next time. That issue is your lighting. Camera settings need to be looked at too.

 

I like that you've gone for a dramatic look. You've got a hard key light source on the left side of your face, but it's too strong. You can see areas of the face where this zero color information. It's gone.

To fix this you can adjust lighting. My guess is that you have no actual video lights and are using the sunlight coming through a bedroom window as your source. Yes? There may even be two windows in this room.

If it were a standard light, you might try to reduce the energy going to that light source by dimming the light, diffusing the light, or moving the light further back from the subject. If the sun and this window is all you have, you can head down to the Walmart and pick up some sheer curtains for my second idea: diffusion. You can layer those up until you get a nice soft light source. Works for me. 

 

The hot spots on the doors behind you can be remedied by flagging it at the source. You might not have grip equipment handy, so you can use household items. A shower curtain hanger pole, some spring clamps, and blackout curtains has helped me cut down hard shadows and blown out areas of the frame. If you like some hotter places in the frame, again, diffusion is your friend.

 

You can also adjust your camera settings and stop down the aperture until you have a more balanced lighting level. Stopping down can affect your depth of field, so keep that in mind. You can use ND filters over your camera lens or physically move the camera to work for you in that area. Above all, you can always shoot a stop or two lower than normal and brighten the exposure in post. It may take some experimentation to get that technique down, though. I like to do this for both photo and video, as you can always brighten up a scene, but once the color information is lost (blown out, or too dark), you can never regain it in post. I like the option of always having control over all the pixels in a frame.

Underexposed 4K frame - iPhone 6s PlusUnderexposed 4K frame - iPhone 6s PlusEven mobile phones can work in gaining control over your shooting situation. I have a cool camera case for my iPhone to handle this - it has a bunch of ND filters. I like to use pro camera apps or even the Rush camera to have more control over my camera. I had a 6S Plus and shot some great 4K with it using the FiLMiC Pro app back in 2016, so keep at it with camera control settings. You can use Auto Exposure to set up a nice balanced lighting level, but then once it's set, you can turn it off. As Neil suggests, an auto iris opening and closing your aperture is very annoying to the viewer.

I hope this advice helps you a bit in getting a better shot next time you create a video. Wishing you the best of luck.

 

Thanks,
Kevin

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Explorer ,
Jun 13, 2021 Jun 13, 2021

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Kevin, thank you so very much for this! The fact that you took your time to write all of that means the world to me 🙂 Much love!

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