Differences between Preview and rendered video

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Julian Wegmann

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Differences between Preview and rendered video

PostThu May 18, 2017 2:55 pm

Hello there!

So i just tried out Davinci Resolve to edit and colorgrade a music video. My problem is that the preview of the
video in D. Resolve looks really good but after rendering the video seems to lose some of the colorgrading and saturation. I rendered with the custom options and youtube 1080p standard options. How can i fix the differences? Hope somebody can help me, thank you!

I made some screenshots of the problem but i'm not allowed to share urls here.


ps.: I'm working with Davinci Resolve 12.5.5.026 on an Macbook Pro 2013 with Mac OS Sierra 10.12.4.
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Julian Wegmann

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Re: Differences between Preview and rendered video

PostThu May 25, 2017 8:14 pm

Alright, nobody seems to face the same problem :|

Today i tried the same thing on my windows pc with Davinci Resolve 12.5. Preview in Davinci and rendered video looks excatly the same. So it seems to be a "Mac problem" i guess..
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Antoine Grasset

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Re: Differences between Preview and rendered video

PostThu May 25, 2017 10:35 pm

What happens if you import your rendered file back into Resolve ? Does it looks good again ?
And what are you using to play your rendered files : Quicktime 7, Quicktime 10, VLC, Youtube ?
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Marc Wielage

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Re: Differences between Preview and rendered video

PostFri May 26, 2017 1:31 am

Two points:

1) don't try to compare what you see in the GUI to what actually gets exported. Only rely on an an external calibrated monitor with a color-managed output.

2) when in doubt, export a few seconds of color bars through the same signal path, then check it on the scopes. If the bars are identical, then the image has not changed. If there is a shift, you'll see it in the levels.
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Antoine Grasset

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Re: Differences between Preview and rendered video

PostFri May 26, 2017 2:30 am

Marc Wielage wrote:1) don't try to compare what you see in the GUI to what actually gets exported. Only rely on an an external calibrated monitor with a color-managed output.


That's where we're headed tough and BMD already implemented changes to encourage relying on the GUI.
IMHO when coloring web-only content it's perfectly fine if your software+hardware setup is right.
For web content, the digital photography and graphic design industries have been going forever without depending upon external monitoring.
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Rami Abou Fakher

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Re: Differences between Preview and rendered video

PostFri May 26, 2017 5:41 am

I had the same issue but I didn't compare between DR preview and my reference monitor in iMac, I tried as Marc he mentioned by using the color bar and import it to DR and I checked the scopes and my reference monitor, and I there were a different in the saturation level (the export version less saturated than the original).
And when I turned off the broadcast safe in the preferences and re-export again the issue is solved.

Sent from my ONEPLUS A3003 using Tapatalk
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Tero Ahlfors

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Re: Differences between Preview and rendered video

PostFri May 26, 2017 8:44 am

Antoine Grasset wrote:For web content, the digital photography and graphic design industries have been going forever without depending upon external monitoring.


Photography and graphic design aren't comparable to grading when it comes to color management and color pipelines. You CAN grade by using the GUI preview if you, or a possible client, don't care that the footage is correct to a certain specification.
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Andrew Kolakowski

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Re: Differences between Preview and rendered video

PostFri May 26, 2017 9:56 am

Why are they not comparable?
Both rely on same principle- work is done on a monitor calibrated to some specification. The only difference is that video is moving, pictures not :)
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Antoine Grasset

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Re: Differences between Preview and rendered video

PostFri May 26, 2017 2:26 pm

Tero Ahlfors wrote:
Antoine Grasset wrote:For web content, the digital photography and graphic design industries have been going forever without depending upon external monitoring.


Photography and graphic design aren't comparable to grading when it comes to color management and color pipelines. You CAN grade by using the GUI preview if you, or a possible client, don't care that the footage is correct to a certain specification.


I'm on board with Andrew, I think they are comparable.
Photography and graphics for web/digital communication are worked and approved on calibrated display with proper GUI color management.
Further more theses days photos and videos can be captured by the same device, processed on the same software, and delivered to the same media (website/instagram/online ads/etc) : pipelines are very much alike.

That being said, there are specific cases where external monitoring is needed :
- color grading for TV/broadcast/cinema = monitoring on external monitor Rec709/projector P3
- photography intended for print = printing Fogra CMYK proofs.


Back to the subject : Julian how is your problem going ?
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Irakly Shanidze

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Re: Differences between Preview and rendered video

PostFri May 26, 2017 10:00 pm

You might want to try unclicking the box "use mac display for preview" in color management tab of the project settings. I know, it sounds strange, but this is exactly what helped me with this problem.
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Julian Wegmann

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Re: Differences between Preview and rendered video

PostMon Jun 05, 2017 2:52 pm

Hello there! Thanks for your answers! Sry for my late reply, but i didn't expect any answer after weeks of no reply to my post.

So if i put my rendered video back in DR it looks good again, darker and more saturation.
On my Mac i use Quick time to compare the DR Preview with the rendered video. On my Windows pc i use VLC but also tried Quicktime, because i know that there are some differences in the colors between the players. But that's not the problem

I also unchecked the "use mac display for preview" but that didn't change anything.
The broadcast safe in the preferences is deactivated by default.

Like i said, the way i "fixed" the problem is to use my Windows PC for Colorgrading in DR. There i don't have to change anything, the preview does look excactly like the rendered video. I think that's how it should be. Im not a professional colorgrader, i was just searching for a programm to cut and color grade some videos for my youtube channel. Tried different programms like Adobe and Final cut, but for me DR is the easiest way to do it. According to the slogan "easy to use, difficult to master".

In conclusion its sad that i couldn't use my mac for this because of the problem. On Windows i have to convert every video with the help of imovie, otherwise DR isn't able to see the files.

btw sry for my english, i'm german :)
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JPOwens

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Re: Differences between Preview and rendered video

PostMon Jun 05, 2017 5:08 pm

Andrew Kolakowski wrote:Why are they not comparable?
Both rely on same principle- work is done on a monitor calibrated to some specification. The only difference is that video is moving, pictures not :)


But they're not. And there is a lot of difference... more than just "one is moving and the other isn't."

More of a distinction needs to be made between "scene-referred" and "display referred" workflows. This is key to understanding the ACES workflow concept. So far a topic that is not well-explained.

This is why there are Input Device Transforms and Output Transforms. These are the real LUTs (if you will) that manage the platform differences. In between are the Look Modification and Reference Rendering Transforms.

If you want to get back to scene-referred, "what the DP saw" then that means working in a value-neutral colorspace. It kind of doesn't help that there are now six of them (ACESxxx), relevant to subtle CG, VFX, and grade requirements. At its core, I can appreciate the attempt to place a collected set of values in a universally-recognized encoding scheme. It is a step toward addressing this other disconnect that is driving threads like this.

Its also not for everybody. You do not need this for 709-709 production. It would be one of those silly things like translating your Basque novel into English so you could fan it out into other languages... but really, its only release is going to be Basque. But you wouldn't consider doing anything with an English original for English release. Is there a flaw in the logic here?


jPo, CSI

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